SQLite

  $(TOP)\src\test_mutex.c \
  $(TOP)\src\test_onefile.c \
  $(TOP)\src\test_osinst.c \
  $(TOP)\src\test_pcache.c \
  $(TOP)\src\test_quota.c \
  $(TOP)\src\test_rtree.c \
  $(TOP)\src\test_schema.c \
  $(TOP)\src\test_schemapool.c \
  $(TOP)\src\test_superlock.c \
  $(TOP)\src\test_syscall.c \
  $(TOP)\src\test_tclsh.c \
  $(TOP)\src\test_tclvar.c \
  $(TOP)\src\test_thread.c \
  $(TOP)\src\test_vdbecov.c \
  $(TOP)\src\test_vfs.c \

<p><tt>%code</tt> is typically used to include some action routines or perhaps
a tokenizer or even the "main()" function
as part of the output file.</p>

<p>There can be multiple <tt>%code</tt> directives.  The arguments of
all <tt>%code</tt> directives are concatenated.</p>

<p>If the argument to <tt>%code</tt> is a filename within <tt>&lt;...&gt;</tt>
then the content of the named file is inserted instead of the text of the
argument itself.

<a id='default_destructor'></a>
<h4>4.4.2 The <tt>%default_destructor</tt> directive</h4>

<p>The <tt>%default_destructor</tt> directive specifies a destructor to
use for non-terminals that do not have their own destructor
specified by a separate <tt>%destructor</tt> directive.  See the documentation

<pre>
   %include {#include &lt;unistd.h&gt;}
</pre>

<p>This might be needed, for example, if some of the C actions in the
grammar call functions that are prototyped in unistd.h.</p>

<p>If the argument to <tt>%include</tt> is a filename within
<tt>&lt;...&gt;</tt> then the content of that file is inserted instead
of the text of the argument itself.


<p>Use the <tt><a href="#pcode">%code</a></tt> directive to add code to
the end of the generated parser.</p>

<a id='pleft'></a>
<h4>4.4.10 The <tt>%left</tt> directive</h4>

Shared-Schema Mode Notes
========================

The [reuse-schema](/timeline?r=reuse-schema) branch contains changes 
to allow SQLite connections to share schemas
between database connections within the same process in order to save memory.
Schemas may be shared between multiple databases attached to the same or
distinct connection handles.

Compile with -DSQLITE\_ENABLE\_SHARED\_SCHEMA in order to enable the
shared-schema enhancement.  Enabling the shared-schema enhancement causes
approximately a 0.1% increase in CPU cycles consumed and about a 3000-byte
increase in the size of the library, even if shared-schema is never used.

Assuming the compile-time requirements are satisfied, the shared-schema
feature is engaged by opening the database connection using the
sqlite3_open_v2() API with the SQLITE_OPEN_SHARED_SCHEMA
flag specified.  The main database and any attached databases will then share
an in-memory Schema object with any other database opened within the process
for which: 

  * the contents of the sqlite_master table, including all object names,
    SQL statements and root pages are identical, and
  * have the same values for the schema-cookie.

Temp databases (those populated with "CREATE TEMP TABLE" and similar
statements) never share schemas.

Connections opened with the SQLITE_OPEN_SHARED_SCHEMA flag
specified may not modify any database schema except that belonging to the
temp database in anyway. This includes creating or dropping database 
objects, vacuuming the database, or running ANALYZE when the
sqlite_stat\[14\] tables do not exist.

For SQLITE_OPEN_SHARED_SCHEMA connections, the
SQLITE_DBSTATUS_SCHEMA_USED sqlite3_db_status() verb
distributes the memory used for a shared schema object evenly between all
database connections that share it.

## The ".shared-schema" Command

The shell tool on this branch contains a special dot-command to help with
managing databases. The ".shared-schema" dot-command can be used to test
whether or not two databases are similar enough to share in-memory schemas,
and to fix minor problems that prevent them from doing so. To test if
two or more database are compatible, one database is opened directly using 
the shell tool and the following command issued:

        .shared-schema check <database-1> [<database-2>]...

where &lt;database-1&gt; etc. are replaced with the names of database files
on disk. For each database specified on the command line, a single line of
output is produced. If the database can share an in-memory schema with the
main database opened by the shell tool, the output is of the form:

        <database> is compatible

Otherwise, if the database cannot share a schema with the main db, the output
is of the form:

        <database> is NOT compatible (<reason>)

where &lt;reason&gt; indicates the cause of the incompatibility. &lt;reason&gt;
is always one of the following.

<ul>
  <li> <b>objects</b> - the databases contain a different set schema objects
  (tables, indexes, views and triggers).

  <li> <b>SQL</b> - the databases contain the same set of objects, but the SQL
  statements used to create them were not the same.

  <li> <b>root pages</b> - the databases contain the same set of objects created
  by the same SQL statements, but the root pages are not the same.

  <li> <b>order of sqlite&#95;master rows</b> - the databases contain the same
  set of objects created by the same SQL statements with the same root pages,
  but the order of the rows in the sqlite&#95;master tables are different.

  <li> <b>schema cookie</b> - the database schemas are compatible, but the 
  schema cookie values ("PRAGMA schema&#95;version") are different.
</ul>

The final three problems in the list above can be fixed using the
.shared-schema command. To modify such a database so that it can share a 
schema with the main database, the following shell command is used:

        .shared-schema fix <database-1> [<database-2>]...

If a database can be modified so that it may share a schema with the main
database opened by the shell tool, output is as follows:

        Fixing <database>... <database> is compatible

If a database does not require modification, or cannot be modified such that
it can share a schema with the main database, the output of "fix" is identical
to that of the "check" command.

## Implementation Notes

A single Schema object is never used by more than one database simultaneously,
regardless of whether or not those databases are attached to the same or
different database handles. Instead, a pool of schema objects is maintained 
for each unique sqlite&#95;master-contents/schema-cookie combination
opened within the process. Each time database schemas are required by a
connection, for example as part of an sqlite3&#95;prepare\*(),
sqlite3&#95;blob&#95;open() or sqlite3&#95;blob&#95;open() call, it obtains
the minimum number of schemas required from the various schema-pools, returning
them at the end of the call. This means that a single schema-pool only ever
contains more than one copy of the schema if:

  * Two threads require schemas from the same pool at the same time, or
  * A single sqlite3&#95;prepare\*() call requires schemas for two or more
    attached databases that use the same schema-pool.

The size of a schema-pool never shrinks. Each schema pool always maintains 
a number of schema objects equal to the highwater mark of schema objects
simultaneously required by clients.

This approach is preferred to allowing multiple databases to use the same
Schema object simultaneously for three reasons:

  * The Schema object is not completely read-only. For example, the 
    Index.zIdxAff string is allocated lazily.
  * Throughout the statement compiler, SQLite uses variables like 
    Table.pSchema and Index.pSchema with the sqlite3SchemaToIndex() routine
    in order to determine which attached database a Table or Index object
    resides in. This mechanism does not work if the same Schema may be
    used by two or more attached databases.
  * It may be easier to modify this approach in order to allow
    SQLITE&#95;OPEN&#95;SHARED&#95;SCHEMA connections to modify database
    schemas, should that be required.

SQLITE&#95;OPEN&#95;SHARED&#95;SCHEMA connections do not store their
virtual-table handles in the Table.pVTable list of each table. This would not
work, as (a) there is no guarantee that a connection will be assigned the same
Schema object each time it requests one from a schema-pool and (b) a single
Schema (and therefore Table) object may correspond to tables in two or more
databases attached to a single connection. Instead, all virtual-table handles
associated with a single database are stored in a linked-list headed at
Db.pVTable.

_fiddle_exec
_fiddle_interrupt
_fiddle_experiment
_fiddle_the_db
_fiddle_db_arg
_fiddle_db_filename
_fiddle_reset_db

_fiddle_db_arg
_fiddle_db_filename
_fiddle_exec
_fiddle_experiment
_fiddle_interrupt
_fiddle_main
_fiddle_reset_db
_fiddle_db_handle
_fiddle_db_vfs
_fiddle_export_db

_sqlite3_bind_blob
_sqlite3_bind_double
_sqlite3_bind_int
_sqlite3_bind_int64
_sqlite3_bind_null
_sqlite3_bind_parameter_count
_sqlite3_bind_parameter_index
_sqlite3_bind_text
_sqlite3_changes
_sqlite3_changes64
_sqlite3_clear_bindings
_sqlite3_close_v2
_sqlite3_column_blob
_sqlite3_column_bytes
_sqlite3_column_count
_sqlite3_column_count
_sqlite3_column_double
_sqlite3_column_int
_sqlite3_column_int64
_sqlite3_column_name
_sqlite3_column_text
_sqlite3_column_type
_sqlite3_compileoption_get
_sqlite3_compileoption_used
_sqlite3_create_function_v2
_sqlite3_data_count
_sqlite3_db_filename
_sqlite3_db_name
_sqlite3_errmsg
_sqlite3_error_offset
_sqlite3_errstr
_sqlite3_exec
_sqlite3_expanded_sql
_sqlite3_extended_errcode
_sqlite3_extended_result_codes
_sqlite3_finalize
_sqlite3_initialize
_sqlite3_interrupt
_sqlite3_libversion
_sqlite3_libversion_number
_sqlite3_open
_sqlite3_open_v2
_sqlite3_prepare_v2
_sqlite3_prepare_v3
_sqlite3_reset
_sqlite3_result_blob
_sqlite3_result_double
_sqlite3_result_error
_sqlite3_result_error_code
_sqlite3_result_error_nomem
_sqlite3_result_error_toobig
_sqlite3_result_int
_sqlite3_result_null
_sqlite3_result_text
_sqlite3_sourceid
_sqlite3_sql
_sqlite3_step
_sqlite3_strglob
_sqlite3_strlike
_sqlite3_total_changes
_sqlite3_total_changes64
_sqlite3_value_blob
_sqlite3_value_bytes
_sqlite3_value_double
_sqlite3_value_text
_sqlite3_value_type
_sqlite3_vfs_find
_sqlite3_vfs_register
_sqlite3_wasm_db_error
_sqlite3_wasm_enum_json
_malloc
_free

_malloc
_free
_realloc
_sqlite3_aggregate_context
_sqlite3_auto_extension
_sqlite3_bind_blob
_sqlite3_bind_double
_sqlite3_bind_int
_sqlite3_bind_int64
_sqlite3_bind_null
_sqlite3_bind_parameter_count
_sqlite3_bind_parameter_index
_sqlite3_bind_parameter_name
_sqlite3_bind_pointer
_sqlite3_bind_text
_sqlite3_busy_handler
_sqlite3_busy_timeout
_sqlite3_cancel_auto_extension
_sqlite3_changes
_sqlite3_changes64
_sqlite3_clear_bindings
_sqlite3_close_v2
_sqlite3_collation_needed
_sqlite3_column_blob
_sqlite3_column_bytes
_sqlite3_column_count
_sqlite3_column_decltype
_sqlite3_column_double
_sqlite3_column_int
_sqlite3_column_int64
_sqlite3_column_name
_sqlite3_column_text
_sqlite3_column_type
_sqlite3_column_value
_sqlite3_commit_hook
_sqlite3_compileoption_get
_sqlite3_compileoption_used
_sqlite3_complete
_sqlite3_context_db_handle
_sqlite3_create_collation
_sqlite3_create_collation_v2
_sqlite3_create_function
_sqlite3_create_function_v2
_sqlite3_data_count
_sqlite3_db_filename
_sqlite3_db_handle
_sqlite3_db_name
_sqlite3_db_readonly
_sqlite3_db_status
_sqlite3_deserialize
_sqlite3_errcode
_sqlite3_errmsg
_sqlite3_error_offset
_sqlite3_errstr
_sqlite3_exec
_sqlite3_expanded_sql
_sqlite3_extended_errcode
_sqlite3_extended_result_codes
_sqlite3_file_control
_sqlite3_finalize
_sqlite3_free
_sqlite3_get_auxdata
_sqlite3_get_autocommit
_sqlite3_initialize
_sqlite3_interrupt
_sqlite3_is_interrupted
_sqlite3_keyword_count
_sqlite3_keyword_name
_sqlite3_keyword_check
_sqlite3_last_insert_rowid
_sqlite3_libversion
_sqlite3_libversion_number
_sqlite3_limit
_sqlite3_malloc
_sqlite3_malloc64
_sqlite3_msize
_sqlite3_open
_sqlite3_open_v2
_sqlite3_overload_function
_sqlite3_prepare_v2
_sqlite3_prepare_v3
_sqlite3_randomness
_sqlite3_realloc
_sqlite3_realloc64
_sqlite3_reset
_sqlite3_reset_auto_extension
_sqlite3_result_blob
_sqlite3_result_double
_sqlite3_result_error
_sqlite3_result_error_code
_sqlite3_result_error_nomem
_sqlite3_result_error_toobig
_sqlite3_result_int
_sqlite3_result_int64
_sqlite3_result_null
_sqlite3_result_pointer
_sqlite3_result_subtype
_sqlite3_result_text
_sqlite3_result_zeroblob
_sqlite3_result_zeroblob64
_sqlite3_rollback_hook
_sqlite3_serialize
_sqlite3_set_auxdata
_sqlite3_set_last_insert_rowid
_sqlite3_shutdown
_sqlite3_sourceid
_sqlite3_sql
_sqlite3_status
_sqlite3_status64
_sqlite3_step
_sqlite3_stmt_busy
_sqlite3_stmt_explain
_sqlite3_stmt_isexplain
_sqlite3_stmt_readonly
_sqlite3_stmt_status
_sqlite3_strglob
_sqlite3_stricmp
_sqlite3_strlike
_sqlite3_strnicmp
_sqlite3_table_column_metadata
_sqlite3_total_changes
_sqlite3_total_changes64
_sqlite3_trace_v2
_sqlite3_txn_state
_sqlite3_update_hook
_sqlite3_uri_boolean
_sqlite3_uri_int64
_sqlite3_uri_key
_sqlite3_uri_parameter
_sqlite3_user_data
_sqlite3_value_blob
_sqlite3_value_bytes
_sqlite3_value_double
_sqlite3_value_dup
_sqlite3_value_free
_sqlite3_value_frombind
_sqlite3_value_int
_sqlite3_value_int64
_sqlite3_value_nochange
_sqlite3_value_numeric_type
_sqlite3_value_pointer
_sqlite3_value_subtype
_sqlite3_value_text
_sqlite3_value_type
_sqlite3_vfs_find
_sqlite3_vfs_register
_sqlite3_vfs_unregister
_sqlite3_vtab_collation
_sqlite3_vtab_distinct
_sqlite3_vtab_in
_sqlite3_vtab_in_first
_sqlite3_vtab_in_next
_sqlite3_vtab_nochange
_sqlite3_vtab_on_conflict
_sqlite3_vtab_rhs_value

//#ifnot omit-oo1
/*
  2022-08-24

  The author disclaims copyright to this source code.  In place of a
  legal notice, here is a blessing:

  *   May you do good and not evil.

   config option may alternately be a function, in which case this
   function re-assigns this property with the result of calling that
   function, enabling delayed instantiation of a Worker.

   - `onready` (optional, but...): this callback is called with no
   arguments when the worker fires its initial
   'sqlite3-api'/'worker1-ready' message, which it does when
   sqlite3.initWorker1API() completes its initialization. This is the
   simplest way to tell the worker to kick off work at the earliest
   opportunity, and the only way to know when the worker module has
   sqlite3.initWorker1API() completes its initialization. This is
   the simplest way to tell the worker to kick off work at the
   earliest opportunity.
   completed loading. The irony of using a callback for this, instead
   of returning a promise from sqlite3Worker1Promiser() is not lost on
   the developers: see sqlite3Worker1Promiser.v2() which uses a
   Promise instead.

   - `onunhandled` (optional): a callback which gets passed the
   message event object for any worker.onmessage() events which
   are not handled by this proxy. Ideally that "should" never
   happen, as this proxy aims to handle all known message types.

   - `generateMessageId` (optional): a function which, when passed an

      columnNames: array}

   Where `typeString` is an internally-synthesized message type string
   used temporarily for worker message dispatching. It can be ignored
   by all client code except that which tests this API. The `row`
   property contains the row result in the form implied by the
   `rowMode` option (defaulting to `'array'`). The `rowNumber` is a
   1-based integer value incremented by 1 on each call into the
   1-based integer value incremented by 1 on each call into th 
   callback.

   At the end of the result set, the same event is fired with
   (row=undefined, rowNumber=null) to indicate that
   the end of the result set has been reached. Note that the rows
   arrive via worker-posted messages, with all the implications
   of that.

   Notable shortcomings:

   - This API was not designed with ES6 modules in mind. Neither Firefox
     nor Safari support, as of March 2023, the {type:"module"} flag to the
     Worker constructor, so that particular usage is not something we're going
     to target for the time being:

     https://developer.mozilla.org/en-US/docs/Web/API/Worker/Worker
*/
globalThis.sqlite3Worker1Promiser = function callee(config = callee.defaultConfig){
self.sqlite3Worker1Promiser = function callee(config = callee.defaultConfig){
  // Inspired by: https://stackoverflow.com/a/52439530
  if(1===arguments.length && 'function'===typeof arguments[0]){
    const f = config;
    config = Object.assign(Object.create(null), callee.defaultConfig);
    config.onready = f;
  }else{
    config = Object.assign(Object.create(null), callee.defaultConfig, config);

  const genMsgId = config.generateMessageId || function(msg){
    return msg.type+'#'+(idTypeMap[msg.type] = (idTypeMap[msg.type]||0) + 1);
  };
  const toss = (...args)=>{throw new Error(args.join(' '))};
  if(!config.worker) config.worker = callee.defaultConfig.worker;
  if('function'===typeof config.worker) config.worker = config.worker();
  let dbId;
  let promiserFunc;
  config.worker.onmessage = function(ev){
    ev = ev.data;
    debug('worker1.onmessage',ev);
    let msgHandler = handlerMap[ev.messageId];
    if(!msgHandler){
      if(ev && 'sqlite3-api'===ev.type && 'worker1-ready'===ev.result) {
        /*fired one time when the Worker1 API initializes*/
        if(config.onready) config.onready(promiserFunc);
        if(config.onready) config.onready();
        return;
      }
      msgHandler = handlerMap[ev.type] /* check for exec per-row callback */;
      if(msgHandler && msgHandler.onrow){
        msgHandler.onrow(ev);
        return;
      }
      }        
      if(config.onunhandled) config.onunhandled(arguments[0]);
      else err("sqlite3Worker1Promiser() unhandled worker message:",ev);
      return;
    }
    delete handlerMap[ev.messageId];
    switch(ev.type){
        case 'error':

          break;
        default:
          break;
    }
    try {msgHandler.resolve(ev)}
    catch(e){msgHandler.reject(e)}
  }/*worker.onmessage()*/;
  return promiserFunc = function(/*(msgType, msgArgs) || (msgEnvelope)*/){
  return function(/*(msgType, msgArgs) || (msgEnvelope)*/){
    let msg;
    if(1===arguments.length){
      msg = arguments[0];
    }else if(2===arguments.length){
      msg = Object.create(null);
      msg.type = arguments[0];
      msg.args = arguments[1];
      msg = {
        type: arguments[0],
        args: arguments[1]
      msg.dbId = msg.args.dbId;
      };
    }else{
      toss("Invalid arguments for sqlite3Worker1Promiser()-created factory.");
      toss("Invalid arugments for sqlite3Worker1Promiser()-created factory.");
    }
    if(!msg.dbId && msg.type!=='open') msg.dbId = dbId;
    if(!msg.dbId) msg.dbId = dbId;
    msg.messageId = genMsgId(msg);
    msg.departureTime = performance.now();
    const proxy = Object.create(null);
    proxy.message = msg;
    let rowCallbackId /* message handler ID for exec on-row callback proxy */;
    if('exec'===msg.type && msg.args){
      if('function'===typeof msg.args.callback){

      debug("Posting",msg.type,"message to Worker dbId="+(dbId||'default')+':',msg);
      config.worker.postMessage(msg);
    });
    if(rowCallbackId) p = p.finally(()=>delete handlerMap[rowCallbackId]);
    return p;
  };
}/*sqlite3Worker1Promiser()*/;

globalThis.sqlite3Worker1Promiser.defaultConfig = {
self.sqlite3Worker1Promiser.defaultConfig = {
  worker: function(){
//#if target=es6-module
    return new Worker(new URL("sqlite3-worker1-bundler-friendly.mjs", import.meta.url),{
//#if target=es6-bundler-friendly
    return new Worker("sqlite3-worker1.js");
      type: 'module'
    });
//#else
    let theJs = "sqlite3-worker1.js";
    if(this.currentScript){
      const src = this.currentScript.src.split('/');
      src.pop();
      theJs = src.join('/')+'/' + theJs;
      //sqlite3.config.warn("promiser currentScript, theJs =",this.currentScript,theJs);
    }else if(globalThis.location){
      //sqlite3.config.warn("promiser globalThis.location =",globalThis.location);
      const urlParams = new URL(globalThis.location.href).searchParams;
    }else{
      //sqlite3.config.warn("promiser self.location =",self.location);
      const urlParams = new URL(self.location.href).searchParams;
      if(urlParams.has('sqlite3.dir')){
        theJs = urlParams.get('sqlite3.dir') + '/' + theJs;
      }
    }
    return new Worker(theJs + globalThis.location.search);
    return new Worker(theJs + self.location.search);
//#endif
  }
//#ifnot target=es6-module
  .bind({
    currentScript: globalThis?.document?.currentScript
  })
  }.bind({
    currentScript: self?.document?.currentScript
  }),
//#endif
  ,
  onerror: (...args)=>console.error('worker1 promiser error',...args)
}/*defaultConfig*/;

/**
   sqlite3Worker1Promiser.v2(), added in 3.46, works identically to
   sqlite3Worker1Promiser() except that it returns a Promise instead
   of relying an an onready callback in the config object. The Promise
   resolves to the same factory function which
   sqlite3Worker1Promiser() returns.

   If config is-a function or is an object which contains an onready
   function, that function is replaced by a proxy which will resolve
   after calling the original function and will reject if that
   function throws.
*/
sqlite3Worker1Promiser.v2 = function(config){
  let oldFunc;
  if( 'function' == typeof config ){
    oldFunc = config;
    config = {};
  }else if('function'===typeof config?.onready){
    oldFunc = config.onready;
    delete config.onready;
  }
};
  const promiseProxy = Object.create(null);
  config = Object.assign((config || Object.create(null)),{
    onready: async function(func){
      try {
        if( oldFunc ) await oldFunc(func);
        promiseProxy.resolve(func);
      }
      catch(e){promiseProxy.reject(e)}
    }
  });
  const p = new Promise(function(resolve,reject){
    promiseProxy.resolve = resolve;
    promiseProxy.reject = reject;
  });
  try{
    this.original(config);
  }catch(e){
    promiseProxy.reject(e);
  }
  return p;
}.bind({
   /* We do this because clients are
      recommended to delete globalThis.sqlite3Worker1Promiser. */
  original: sqlite3Worker1Promiser
});

//#if target=es6-module
/**
  When built as a module, we export sqlite3Worker1Promiser.v2()
  instead of sqlite3Worker1Promise() because (A) its interface is more
  conventional for ESM usage and (B) the ESM export option for this
  API did not exist until v2 was created, so there's no backwards
  incompatibility.
*/
export default sqlite3Worker1Promiser.v2;
//#endif /* target=es6-module */
//#else
/* Built with the omit-oo1 flag. */
//#endif ifnot omit-oo1

    const mustNotReach = ()=>toss("This is not supposed to be reached.");

    await wtest('exec',{
      sql: ["create table t(a,b)",
            "insert into t(a,b) values(1,2),(3,4),(5,6)"
           ].join(';'),
      resultRows: [], columnNames: [],
      lastInsertRowId: true,
      countChanges: sqConfig.bigIntEnabled ? 64 : true
    }, function(ev){
      ev = ev.result;
      T.assert(0===ev.resultRows.length)
        .assert(0===ev.columnNames.length)
        .assert(sqConfig.bigIntEnabled
                ? (3n===ev.changeCount)
                : (3===ev.changeCount))
                : (3===ev.changeCount));
        .assert('bigint'===typeof ev.lastInsertRowId)
        .assert(ev.lastInsertRowId>=3);
    });

    await wtest('exec',{
      sql: 'select a a, b b from t order by a',
      resultRows: [], columnNames: [],
    }, function(ev){
      ev = ev.result;

<!doctype html>
<html lang="en-us">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>SQLite3 Fiddle</title>
    <link rel="shortcut icon" href="data:image/x-icon;," type="image/x-icon">
    <!-- to add a togglable terminal-style view, uncomment the following
         two lines and ensure that these files are on the web server. -->
    <!--script src="jqterm/jqterm-bundle.min.js"></script>
    <link rel="stylesheet" href="jqterm/jquery.terminal.min.css"/-->
    <link rel="stylesheet" href="emscripten.css"/>
    <style>
      /* The following styles are for app-level use. */
      :root {
          --sqlite-blue: #044a64;
          --textarea-color1: #044a64;
          --textarea-color2: white;
      }
      textarea {
          font-family: monospace;
          flex: 1 1 auto;
          background-color: var(--textarea-color1);
          color: var(--textarea-color2);
      }
      textarea#input {
          color: var(--textarea-color1);
          background-color: var(--textarea-color2);
      }
      header {
          display: flex;
          justify-content: space-between;
          align-items: center;
          background-color: var(--sqlite-blue);
          color: white;
          font-size: 120%;
          font-weight: bold;
          border-radius: 0.25em;
          padding: 0.2em 0.5em;
      }
      header > .powered-by {
          font-size: 80%;
      }
      header a, header a:visited, header a:hover {
          color: inherit;
      }
      #main-wrapper {
          display: flex;
          flex-direction: column-reverse;
          flex: 1 1 auto;
          margin: 0.5em 0;
          overflow: hidden;
      }
      #main-wrapper.side-by-side {
          flex-direction: row;
      }
      #main-wrapper.side-by-side > fieldset {
          margin-left: 0.25em;
          margin-right: 0.25em;
      }
      #main-wrapper:not(.side-by-side) > fieldset {
          margin-bottom: 0.25em;
      }
      #main-wrapper.swapio {
          flex-direction: column;
      }
      #main-wrapper.side-by-side.swapio {
          flex-direction: row-reverse;
      }
      .zone-wrapper{
          display: flex;
          margin: 0;
          flex: 1 1 0%;
          border-radius: 0.5em;
          min-width: inherit/*important: resolves inability to scroll fieldset child element!*/;
          padding: 0.35em 0 0 0;
      }
      .zone-wrapper textarea {
          border-radius: 0.5em;
          flex: 1 1 auto;
          /*min/max width resolve an inexplicable margin on the RHS.  The -1em
            is for the padding, else we overlap the parent boundaries.*/
          /*min-width: calc(100% - 1em);
          max-width: calc(100% - 1em);
          padding: 0 0.5em;*/
      }

      .zone-wrapper.input { flex: 10 1 auto; }
      .zone-wrapper.output { flex: 20 1 auto; }
      .zone-wrapper > div {
          display:flex;
          flex: 1 1 0%;
      }
      .zone-wrapper.output {}
      .button-bar {
          display: flex;
          flex-wrap: wrap;
          align-items: center;
          align-content: space-between;
          justify-content: flex-start;
      }
      .button-bar > * {
          margin: 0.05em 0.5em 0.05em 0;
          flex: 0 1 auto;
          align-self: auto;
      }
      label[for] {
          cursor: pointer;
      }
      .error {
          color: red;
          background-color: yellow;
      }
      .hidden, .initially-hidden {
          position: absolute !important;
          opacity: 0 !important;
          pointer-events: none !important;
          display: none !important;
      }
      fieldset {
          border-radius: 0.5em;
          border: 1px inset;
          padding: 0.25em;
      }
      fieldset.options {
          font-size: 80%;
          margin-top: 0.5em;
      }
      fieldset:not(.options) > legend {
          font-size: 80%;
      }
      fieldset.options > div {
          display: flex;
          flex-wrap: wrap;
      }
      fieldset button {
          font-size: inherit;
      }
      fieldset.collapsible > legend > .fieldset-toggle::after {
          content: " [hide]";
          position: relative;
      }
      fieldset.collapsible.collapsed > legend > .fieldset-toggle::after {
          content: " [show]";
          position: relative;
      }
      span.labeled-input {
          padding: 0.25em;
          margin: 0.05em 0.25em;
          border-radius: 0.25em;
          white-space: nowrap;
          background: #0002;
          display: flex;
          align-items: center;
      }
      span.labeled-input > *:nth-child(2) {
          margin-left: 0.3em;
      }
      .center { text-align: center; }
      body.terminal-mode {
          max-height: calc(100% - 2em);
          display: flex;
          flex-direction: column;
          align-items: stretch;
      }
      #view-terminal {}
      .app-view {
          flex: 20 1 auto;
      }
      #view-split {
          display: flex;
          flex-direction: column-reverse;
      }
    </style>
  </head>
  <body>
    <header id='titlebar'>
      <span>SQLite3 Fiddle</span>
      <span class='powered-by'>Powered by
        <a href='https://sqlite.org'>SQLite3</a></span>
    </header>
    <!-- emscripten bits -->
    <figure id="module-spinner">
      <div class="spinner"></div>
      <div class='center'><strong>Initializing app...</strong></div>
      <div class='center'>
        On a slow internet connection this may take a moment.  If this
        message displays for "a long time", intialization may have
        failed and the JavaScript console may contain clues as to why.
      </div>
    </figure>
    <div class="emscripten" id="module-status">Downloading...</div>
    <div class="emscripten">
      <progress value="0" max="100" id="module-progress" hidden='1'></progress>  
    </div><!-- /emscripten bits -->

    <div id='view-terminal' class='app-view hidden initially-hidden'>
      This is a placeholder for a terminal-like view which is not in
      the default build.
    </div>

    <div id='view-split' class='app-view initially-hidden'>
      <fieldset class='options collapsible'>
        <legend><button class='fieldset-toggle'>Options</button></legend>
        <div class=''>
          <span class='labeled-input'>
            <input type='checkbox' id='opt-cb-sbs'
                   data-csstgt='#main-wrapper'
                   data-cssclass='side-by-side'
                   data-config='sideBySide'>
            <label for='opt-cb-sbs'>Side-by-side</label>
          </span>
          <span class='labeled-input'>
            <input type='checkbox' id='opt-cb-swapio'
                   data-csstgt='#main-wrapper'
                   data-cssclass='swapio'
                   data-config='swapInOut'>
            <label for='opt-cb-swapio'>Swap in/out</label>
          </span>
          <span class='labeled-input'>
            <input type='checkbox' id='opt-cb-autoscroll'
                   data-config='autoScrollOutput'>
            <label for='opt-cb-autoscroll'>Auto-scroll output</label>
          </span>
          <span class='labeled-input'>
            <input type='checkbox' id='opt-cb-autoclear'
                   data-config='autoClearOutput'>
            <label for='opt-cb-autoclear'>Auto-clear output</label>
          </span>
          <span class='labeled-input'>
            <input type='file' id='load-db' class='hidden'/>
            <button id='btn-load-db'>Load DB...</button>
          </span>
          <span class='labeled-input'>
            <button id='btn-export'>Download DB</button>
          </span>
          <span class='labeled-input'>
            <button id='btn-reset'>Reset DB</button>
          </span>
        </div>
      </fieldset><!-- .options -->
      <div id='main-wrapper' class=''>
        <fieldset class='zone-wrapper input'>
          <legend><div class='button-bar'>
            <button id='btn-shell-exec'>Run</button>
            <button id='btn-clear'>Clear Input</button>
            <!--button data-cmd='.help'>Help</button-->
            <select id='select-examples'></select>
          </div></legend>
          <div><textarea id="input"
                         placeholder="Shell input. Ctrl-enter/shift-enter runs it.">
-- ==================================================
-- Use ctrl-enter or shift-enter to execute sqlite3
-- shell commands and SQL.
-- If a subset of the text is currently selected,
-- only that part is executed.
-- ==================================================
.nullvalue NULL
.headers on
</textarea></div>
        </fieldset>
        <fieldset class='zone-wrapper output'>
          <legend><div class='button-bar'>
            <button id='btn-clear-output'>Clear Output</button>
            <button id='btn-interrupt' class='hidden' disabled>Interrupt</button>
            <!-- interruption cannot work in the current configuration
                 because we cannot send an interrupt message when work
                 is currently underway. At that point the Worker is
                 tied up and will not receive the message. -->
          </div></legend>
          <div><textarea id="output" readonly
                         placeholder="Shell output."></textarea></div>
        </fieldset>
      </div>
    </div> <!-- #view-split -->
    <!-- Maintenance notes:

        ... TODO... currently being refactored...

    -->
    <script src="fiddle.js"></script>
  </body>
</html>

<!doctype html>
<html lang="en-us">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>SQLite3 Fiddle</title>
    <link rel="shortcut icon" href="data:image/x-icon;," type="image/x-icon">
    <!-- to add a toggleable terminal-style view, uncomment the following
         two lines and ensure that these files are on the web server. -->
    <!--script src="jqterm/jqterm-bundle.min.js"></script>
    <link rel="stylesheet" href="jqterm/jquery.terminal.min.css"/-->
    <style>
      /* The following styles are for app-level use. */
      :root {
          --sqlite-blue: #044a64;
          --textarea-color1: #044a64;
          --textarea-color2: white;
      }
      textarea {
          font-family: monospace;
          flex: 1 1 auto;
          background-color: var(--textarea-color1);
          color: var(--textarea-color2);
      }
      textarea#input {
          color: var(--textarea-color1);
          background-color: var(--textarea-color2);
      }
      header {
          display: flex;
          justify-content: space-between;
          align-items: center;
          background-color: var(--sqlite-blue);
          color: white;
          font-size: 120%;
          font-weight: bold;
          border-radius: 0.25em;
          padding: 0.2em 0.5em;
      }
      header > .powered-by {
          font-size: 80%;
      }
      header a, header a:visited, header a:hover {
          color: inherit;
      }
      #main-wrapper {
          display: flex;
          flex-direction: column-reverse;
          flex: 1 1 auto;
          margin: 0.5em 0;
          overflow: hidden;
      }
      #main-wrapper.side-by-side {
          flex-direction: row;
      }
      #main-wrapper.side-by-side > fieldset {
          margin-left: 0.25em;
          margin-right: 0.25em;
      }
      #main-wrapper:not(.side-by-side) > fieldset {
          margin-bottom: 0.25em;
      }
      #main-wrapper.swapio {
          flex-direction: column;
      }
      #main-wrapper.side-by-side.swapio {
          flex-direction: row-reverse;
      }
      .zone-wrapper{
          display: flex;
          margin: 0;
          flex: 1 1 0%;
          border-radius: 0.5em;
          min-width: inherit/*important: resolves inability to scroll fieldset child element!*/;
          padding: 0.35em 0 0 0;
      }
      .zone-wrapper textarea {
          border-radius: 0.5em;
          flex: 1 1 auto;
          /*min/max width resolve an inexplicable margin on the RHS.  The -1em
            is for the padding, else we overlap the parent boundaries.*/
          /*min-width: calc(100% - 1em);
          max-width: calc(100% - 1em);
          padding: 0 0.5em;*/
      }

      .zone-wrapper.input { flex: 10 1 auto; }
      .zone-wrapper.output { flex: 20 1 auto; }
      .zone-wrapper > div {
          display:flex;
          flex: 1 1 0%;
      }
      .zone-wrapper.output {}
      .button-bar {
          display: flex;
          flex-wrap: wrap;
          align-items: center;
          align-content: space-between;
          justify-content: flex-start;
      }
      .button-bar > * {
          margin: 0.05em 0.5em 0.05em 0;
          flex: 0 1 auto;
          align-self: auto;
      }
      label[for] {
          cursor: pointer;
      }
      .error {
          color: red;
          background-color: yellow;
      }
      .hidden, .initially-hidden {
          position: absolute !important;
          opacity: 0 !important;
          pointer-events: none !important;
          display: none !important;
      }
      fieldset {
          border-radius: 0.5em;
          border: 1px inset;
          padding: 0.25em;
      }
      fieldset.options {
          font-size: 80%;
          margin-top: 0.5em;
      }
      fieldset:not(.options) > legend {
          font-size: 80%;
      }
      fieldset.options > div {
          display: flex;
          flex-wrap: wrap;
      }
      fieldset button {
          font-size: inherit;
      }
      fieldset.collapsible > legend > .fieldset-toggle::after {
          content: " [hide]";
          position: relative;
      }
      fieldset.collapsible.collapsed > legend > .fieldset-toggle::after {
          content: " [show]";
          position: relative;
      }
      span.labeled-input {
          padding: 0.25em;
          margin: 0.05em 0.25em;
          border-radius: 0.25em;
          white-space: nowrap;
          background: #0002;
          display: flex;
          align-items: center;
      }
      span.labeled-input > *:nth-child(2) {
          margin-left: 0.3em;
      }
      .center { text-align: center; }
      body.terminal-mode {
          max-height: calc(100% - 2em);
          display: flex;
          flex-direction: column;
          align-items: stretch;
      }
      #view-terminal {}
      .app-view {
          flex: 20 1 auto;
      }
      #view-split {
          display: flex;
          flex-direction: column-reverse;
      }

      /* emcscript-related styling, used during the module load/intialization processes... */
      .emscripten { padding-right: 0; margin-left: auto; margin-right: auto; display: block; }
      div.emscripten { text-align: center; }
      div.emscripten_border { border: 1px solid black; }
      #module-spinner { overflow: visible; }
      #module-spinner > * {
          margin-top: 1em;
      }
      .spinner {
          height: 50px;
          width: 50px;
          margin: 0px auto;
          animation: rotation 0.8s linear infinite;
          border-left: 10px solid rgb(0,150,240);
          border-right: 10px solid rgb(0,150,240);
          border-bottom: 10px solid rgb(0,150,240);
          border-top: 10px solid rgb(100,0,200);
          border-radius: 100%;
          background-color: rgb(200,100,250);
      }
      @keyframes rotation {
          from {transform: rotate(0deg);}
          to {transform: rotate(360deg);}
      }
    </style>
  </head>
  <body>
    <header id='titlebar'>
      <span>SQLite3 Fiddle</span>
      <span class='powered-by'>Powered by
        <a href='https://sqlite.org'>SQLite3</a></span>
    </header>
    <!-- emscripten bits -->
    <figure id="module-spinner">
      <div class="spinner"></div>
      <div class='center'><strong>Initializing app...</strong></div>
      <div class='center'>
        On a slow internet connection this may take a moment.  If this
        message displays for "a long time", intialization may have
        failed and the JavaScript console may contain clues as to why.
      </div>
    </figure>
    <div class="emscripten" id="module-status">Downloading...</div>
    <div class="emscripten">
      <progress value="0" max="100" id="module-progress" hidden='1'></progress>  
    </div><!-- /emscripten bits -->

    <div id='view-terminal' class='app-view hidden initially-hidden'>
      This is a placeholder for a terminal-like view which is not in
      the default build.
    </div>

    <div id='view-split' class='app-view initially-hidden'>
      <fieldset class='options collapsible'>
        <legend><button class='fieldset-toggle'>Options</button></legend>
        <div class=''>
          <span class='labeled-input'>
            <input type='checkbox' id='opt-cb-sbs'
                   data-csstgt='#main-wrapper'
                   data-cssclass='side-by-side'
                   data-config='sideBySide'>
            <label for='opt-cb-sbs'>Side-by-side</label>
          </span>
          <span class='labeled-input'>
            <input type='checkbox' id='opt-cb-swapio'
                   data-csstgt='#main-wrapper'
                   data-cssclass='swapio'
                   data-config='swapInOut'>
            <label for='opt-cb-swapio'>Swap in/out</label>
          </span>
          <span class='labeled-input'>
            <input type='checkbox' id='opt-cb-autoscroll'
                   data-config='autoScrollOutput'>
            <label for='opt-cb-autoscroll'>Auto-scroll output</label>
          </span>
          <span class='labeled-input'>
            <input type='checkbox' id='opt-cb-autoclear'
                   data-config='autoClearOutput'>
            <label for='opt-cb-autoclear'>Auto-clear output</label>
          </span>
          <span class='labeled-input'>
            <input type='file' id='load-db' class='hidden'/>
            <button id='btn-load-db'>Load DB...</button>
          </span>
          <span class='labeled-input'>
            <button id='btn-export'>Download DB</button>
          </span>
          <span class='labeled-input'>
            <button id='btn-reset'>Reset DB</button>
          </span>
        </div>
      </fieldset><!-- .options -->
      <div id='main-wrapper' class=''>
        <fieldset class='zone-wrapper input'>
          <legend><div class='button-bar'>
            <button id='btn-shell-exec'>Run</button>
            <button id='btn-clear'>Clear Input</button>
            <!--button data-cmd='.help'>Help</button-->
            <select id='select-examples'></select>
          </div></legend>
          <div><textarea id="input"
                         placeholder="Shell input. Ctrl-enter/shift-enter runs it.">
-- ==================================================
-- Use ctrl-enter or shift-enter to execute sqlite3
-- shell commands and SQL.
-- If a subset of the text is currently selected,
-- only that part is executed.
-- ==================================================
.nullvalue NULL
.headers on
</textarea></div>
        </fieldset>
        <fieldset class='zone-wrapper output'>
          <legend><div class='button-bar'>
            <button id='btn-clear-output'>Clear Output</button>
            <button id='btn-interrupt' class='hidden' disabled>Interrupt</button>
            <!-- interruption cannot work in the current configuration
                 because we cannot send an interrupt message when work
                 is currently underway. At that point the Worker is
                 tied up and will not receive the message. -->
          </div></legend>
          <div><textarea id="output" readonly
                         placeholder="Shell output."></textarea></div>
        </fieldset>
      </div>
    </div> <!-- #view-split -->
    <script src="fiddle.js"></script>
  </body>
</html>

  $(TOP)/src/test_mutex.c \
  $(TOP)/src/test_onefile.c \
  $(TOP)/src/test_osinst.c \
  $(TOP)/src/test_pcache.c \
  $(TOP)/src/test_quota.c \
  $(TOP)/src/test_rtree.c \
  $(TOP)/src/test_schema.c \
  $(TOP)/src/test_schemapool.c \
  $(TOP)/src/test_superlock.c \
  $(TOP)/src/test_syscall.c \
  $(TOP)/src/test_tclsh.c \
  $(TOP)/src/test_tclvar.c \
  $(TOP)/src/test_thread.c \
  $(TOP)/src/test_vdbecov.c \
  $(TOP)/src/test_vfs.c \

#
TESTSRC2 = \
  $(TOP)/src/attach.c \
  $(TOP)/src/backup.c \
  $(TOP)/src/bitvec.c \
  $(TOP)/src/btree.c \
  $(TOP)/src/build.c \
  $(TOP)/src/callback.c \
  $(TOP)/src/ctime.c \
  ctime.c \
  $(TOP)/src/date.c \
  $(TOP)/src/dbpage.c \
  $(TOP)/src/dbstat.c \
  $(TOP)/src/expr.c \
  $(TOP)/src/func.c \
  $(TOP)/src/global.c \

** Generate code to reload the schema for database iDb. And, if iDb!=1, for
** the temp database as well.
*/
static void renameReloadSchema(Parse *pParse, int iDb, u16 p5){
  Vdbe *v = pParse->pVdbe;
  if( v ){
    sqlite3ChangeCookie(pParse, iDb);
    sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, iDb, 0, p5);
    if( iDb!=1 ) sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, 1, 0, p5);
    sqlite3VdbeAddParseSchemaOp(pParse, iDb, 0, p5);
    if( iDb!=1 ) sqlite3VdbeAddParseSchemaOp(pParse, 1, 0, p5);
  }
}

/*
** Generate code to implement the "ALTER TABLE xxx RENAME TO yyy"
** command.
*/

    aCreateTbl[i] = 0;
    if( (pStat = sqlite3FindTable(db, zTab, pDb->zDbSName))==0 ){
      if( i<nToOpen ){
        /* The sqlite_statN table does not exist. Create it. Note that a 
        ** side-effect of the CREATE TABLE statement is to leave the rootpage 
        ** of the new table in register pParse->regRoot. This is important 
        ** because the OpenWrite opcode below will be needing it. */
        sqlite3SchemaWritable(pParse, iDb);
        sqlite3NestedParse(pParse,
            "CREATE TABLE %Q.%s(%s)", pDb->zDbSName, zTab, aTable[i].zCols
        );
        assert( pParse->isCreate || pParse->nErr );
        aRoot[i] = (u32)pParse->u1.cr.regRoot;
        aCreateTbl[i] = OPFLAG_P2ISREG;
      }

  /* If the file was opened successfully, read the schema for the new database.
  ** If this fails, or if opening the file failed, then close the file and 
  ** remove the entry from the db->aDb[] array. i.e. put everything back the
  ** way we found it.
  */
  if( rc==SQLITE_OK ){
    sqlite3BtreeEnterAll(db);
    db->init.iDb = 0;
    db->mDbFlags &= ~(DBFLAG_SchemaKnownOk);
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
    if( db->setlkFlags & SQLITE_SETLK_BLOCK_ON_CONNECT ){
      int val = 1;
      sqlite3_file *fd = sqlite3PagerFile(sqlite3BtreePager(pNew->pBt));
      sqlite3OsFileControlHint(fd, SQLITE_FCNTL_BLOCK_ON_CONNECT, &val);
    }
#endif
    if( !REOPEN_AS_MEMDB(db) ){
    if( !IsSharedSchema(db) && !REOPEN_AS_MEMDB(db) ){
      sqlite3BtreeEnterAll(db);
      rc = sqlite3Init(db, &zErrDyn);
    }
    sqlite3BtreeLeaveAll(db);
    assert( zErrDyn==0 || rc!=SQLITE_OK );
      sqlite3BtreeLeaveAll(db);
      assert( zErrDyn==0 || rc!=SQLITE_OK );
    }
  }
  if( rc ){
    if( ALWAYS(!REOPEN_AS_MEMDB(db)) ){
      int iDb = db->nDb - 1;
      assert( iDb>=2 );
      if( db->aDb[iDb].pBt ){
        sqlite3BtreeClose(db->aDb[iDb].pBt);

    Trigger *pTrig = (Trigger*)sqliteHashData(pEntry);
    if( pTrig->pTabSchema==pDb->pSchema ){
      pTrig->pTabSchema = pTrig->pSchema;
    }
    pEntry = sqliteHashNext(pEntry);
  }

  (void)sqlite3SchemaDisconnect(db, i, 0);
  sqlite3BtreeClose(pDb->pBt);
  pDb->pBt = 0;
  pDb->pSchema = 0;
  sqlite3CollapseDatabaseArray(db);
  return;

detach_error:

){
  int rc;
  NameContext sName;
  Vdbe *v;
  sqlite3* db = pParse->db;
  int regArgs;

  if( (db->mDbFlags & DBFLAG_EncodingFixed)==0 ){
  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ) goto attach_end;
    if( SQLITE_OK!=sqlite3ReadSchema(pParse) ) goto attach_end;
  }

  if( pParse->nErr ) goto attach_end;
  memset(&sName, 0, sizeof(NameContext));
  sName.pParse = pParse;

  if( 
      SQLITE_OK!=resolveAttachExpr(&sName, pFilename) ||

  sqlite3RunParser(pParse, zSql);
  db->mDbFlags = savedDbFlags;
  sqlite3DbFree(db, zSql);
  memcpy(PARSE_TAIL(pParse), saveBuf, PARSE_TAIL_SZ);
  pParse->nested--;
}

#ifdef SQLITE_ENABLE_SHARED_SCHEMA
/*
** If this database connection was opened with the SQLITE_OPEN_SHARED_SCHEMA
** flag specified, then ensure that the database schema for database iDb
** is loaded. Either by obtaining a Schema object from the schema-pool, or
** by reading the contents of the sqlite_master table. Unless it is NULL, 
** the location indicated by parameter pbUnload is set to 1 if a shared-schema 
** is loaded.
**
** If the database handle was not opened with SQLITE_OPEN_SHARED_SCHEMA, or
** if the schema for database iDb is already loaded, this function is a no-op.
**
** SQLITE_OK is returned if successful, or an SQLite error code otherwise. If
** an error code is returned, (*pzErr) may be set to point to a buffer
** containing an error message. It is the responsibility of the caller to
** eventually free this buffer using sqlite3_free().
*/
int sqlite3SchemaLoad(sqlite3 *db, int iDb, int *pbUnload, char **pzErr){
  int rc = SQLITE_OK;
  if( IsSharedSchema(db) 
      && DbHasProperty(db, iDb, DB_SchemaLoaded)==0 
      && (db->init.busy==0 || (iDb!=1 && db->init.iDb==1))
  ){
    struct sqlite3InitInfo sv = db->init;
    memset(&db->init, 0, sizeof(struct sqlite3InitInfo));
    rc = sqlite3InitOne(db, iDb, pzErr, 0);
    db->init = sv;
    if( pbUnload && rc==SQLITE_OK && iDb!=1 ) *pbUnload = 1;
  }
  return rc;
}
#endif

/*
** Locate the in-memory structure that describes a particular database
** table given the name of that table and (optionally) the name of the
** database containing the table.  Return NULL if not found.
**
** If zDatabase is 0, all databases are searched for the table and the
** first matching table is returned.  (No checking for duplicate table
** names is done.)  The search order is TEMP first, then MAIN, then any
** auxiliary databases added using the ATTACH command.
**
** See also sqlite3LocateTable().
*/
Table *sqlite3FindTable(sqlite3 *db, const char *zName, const char *zDatabase){
  Table *p = 0;
  int i;

  /* All mutexes are required for schema access.  Make sure we hold them. */
  assert( zDatabase!=0 || sqlite3BtreeHoldsAllMutexes(db) );
  if( zDatabase ){
    for(i=0; i<db->nDb; i++){
      if( sqlite3StrICmp(zDatabase, db->aDb[i].zDbSName)==0 ) break;
  while(1){
    for(i=OMIT_TEMPDB; i<db->nDb; i++){
      int j = (i<2) ? i^1 : i;   /* Search TEMP before MAIN */
    }
    if( i>=db->nDb ){
      /* No match against the official names.  But always match "main"
      ** to schema 0 as a legacy fallback. */
      if( sqlite3StrICmp(zDatabase,"main")==0 ){
        i = 0;
      }else{
        return 0;
      }
    }
    p = sqlite3HashFind(&db->aDb[i].pSchema->tblHash, zName);
      if( zDatabase==0 || sqlite3DbIsNamed(db, j, zDatabase) ){
        int bUnload = 0;
        assert( sqlite3SchemaMutexHeld(db, j, 0) );
        if( IsSharedSchema(db) ){
          Parse *pParse = db->pParse;
          if( pParse && pParse->nErr==0 ){
            pParse->rc = sqlite3SchemaLoad(db, j, &bUnload, &pParse->zErrMsg);
            if( pParse->rc ) pParse->nErr++;
          }
        }
        p = sqlite3HashFind(&db->aDb[j].pSchema->tblHash, zName);
    if( p==0 && sqlite3StrNICmp(zName, "sqlite_", 7)==0 ){
      if( i==1 ){
        if( p ) return p;
        if( sqlite3StrICmp(zName+7, &PREFERRED_TEMP_SCHEMA_TABLE[7])==0
         || sqlite3StrICmp(zName+7, &PREFERRED_SCHEMA_TABLE[7])==0
         || sqlite3StrICmp(zName+7, &LEGACY_SCHEMA_TABLE[7])==0
        ){
          p = sqlite3HashFind(&db->aDb[1].pSchema->tblHash,
        if( bUnload ){
          sqlite3SchemaRelease(db, j);
                              LEGACY_TEMP_SCHEMA_TABLE);
        }
      }else{
        if( sqlite3StrICmp(zName+7, &PREFERRED_SCHEMA_TABLE[7])==0 ){
      }
    }
    /* Not found.  If the name we were looking for was temp.sqlite_master
    ** then change the name to sqlite_temp_master and try again. */
    if( sqlite3StrICmp(zName, PREFERRED_SCHEMA_TABLE)==0 ){
          p = sqlite3HashFind(&db->aDb[i].pSchema->tblHash,
                              LEGACY_SCHEMA_TABLE);
        }
      zName = LEGACY_SCHEMA_TABLE;
      continue;
    }
      }
    }
  }else{
    /* Match against TEMP first */
    p = sqlite3HashFind(&db->aDb[1].pSchema->tblHash, zName);
    if( p ) return p;
    /* The main database is second */
    p = sqlite3HashFind(&db->aDb[0].pSchema->tblHash, zName);
    if( p ) return p;
    /* Attached databases are in order of attachment */
    for(i=2; i<db->nDb; i++){
      assert( sqlite3SchemaMutexHeld(db, i, 0) );
      p = sqlite3HashFind(&db->aDb[i].pSchema->tblHash, zName);
    if( sqlite3StrICmp(zName, PREFERRED_TEMP_SCHEMA_TABLE)==0 ){
      zName = LEGACY_TEMP_SCHEMA_TABLE;
      if( p ) break;
      continue;
    }
    if( p==0 && sqlite3StrNICmp(zName, "sqlite_", 7)==0 ){
      if( sqlite3StrICmp(zName+7, &PREFERRED_SCHEMA_TABLE[7])==0 ){
    if( sqlite3StrICmp(zName, LEGACY_SCHEMA_TABLE)!=0 ) break;
        p = sqlite3HashFind(&db->aDb[0].pSchema->tblHash, LEGACY_SCHEMA_TABLE);
      }else if( sqlite3StrICmp(zName+7, &PREFERRED_TEMP_SCHEMA_TABLE[7])==0 ){
        p = sqlite3HashFind(&db->aDb[1].pSchema->tblHash,
                            LEGACY_TEMP_SCHEMA_TABLE);
      }
    if( sqlite3_stricmp(zDatabase, db->aDb[1].zDbSName)!=0 ) break;
    zName = LEGACY_TEMP_SCHEMA_TABLE;
  }
    }
  }
  return p;
  return 0;
}

/*
** Locate the in-memory structure that describes a particular database
** table given the name of that table and (optionally) the name of the
** database containing the table.  Return NULL if not found.  Also leave an
** error message in pParse->zErrMsg.

){
  Table *p;
  sqlite3 *db = pParse->db;

  /* Read the database schema. If an error occurs, leave an error message
  ** and code in pParse and return NULL. */
  if( (db->mDbFlags & DBFLAG_SchemaKnownOk)==0
   && !IsSharedSchema(db)
   && SQLITE_OK!=sqlite3ReadSchema(pParse)
  ){
    return 0;
  }

  p = sqlite3FindTable(db, zName, zDbase);
  if( p==0 ){
#ifndef SQLITE_OMIT_VIRTUALTABLE
    /* If zName is the not the name of a table in the schema created using
    ** CREATE, then check to see if it is the name of an virtual table that
    ** can be an eponymous virtual table. */
    if( (pParse->prepFlags & SQLITE_PREPARE_NO_VTAB)==0 && db->init.busy==0 ){
      Module *pMod = (Module*)sqlite3HashFind(&db->aModule, zName);
      if( pMod==0 && sqlite3_strnicmp(zName, "pragma_", 7)==0 ){
        pMod = sqlite3PragmaVtabRegister(db, zName);
      }
      if( pMod ){
        if( IsSharedSchema(db) && pParse->nErr==0 ){
          int bDummy = 0;
          pParse->rc = sqlite3SchemaLoad(db, 0, &bDummy, &pParse->zErrMsg);
          if( pParse->rc ) pParse->nErr++;
          (void)bDummy;
        }
      if( pMod && sqlite3VtabEponymousTableInit(pParse, pMod) ){
        testcase( pMod->pEpoTab==0 );
        return pMod->pEpoTab;
        if( sqlite3VtabEponymousTableInit(pParse, pMod) ){
          Table *pEpoTab = pMod->pEpoTab;
          if( pEpoTab ){
            assert( IsSharedSchema(db)||pEpoTab->pSchema==db->aDb[0].pSchema );
            pEpoTab->pSchema = db->aDb[0].pSchema;  /* For SHARED_SCHEMA mode */
          }
          return pEpoTab;
        }
      }
    }
#endif
    if( flags & LOCATE_NOERR ) return 0;
    pParse->checkSchema = 1;
  }else if( IsVirtual(p) && (pParse->prepFlags & SQLITE_PREPARE_NO_VTAB)!=0 ){
    p = 0;
  }

  if( p==0 ){
  if( p==0 && (!IsSharedSchema(db) || pParse->nErr==0) ){
    const char *zMsg = flags & LOCATE_VIEW ? "no such view" : "no such table";
    if( zDbase ){
      sqlite3ErrorMsg(pParse, "%s: %s.%s", zMsg, zDbase, zName);
    }else{
      sqlite3ErrorMsg(pParse, "%s: %s", zMsg, zName);
    }
  }else{
    assert( HasRowid(p) || p->iPKey<0 );
  }

  return p;
}

/*
** Locate the table identified by *p.

  if( iDb>=0 ){
    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
    DbSetProperty(db, iDb, DB_ResetWanted);
    DbSetProperty(db, 1, DB_ResetWanted);
    db->mDbFlags &= ~DBFLAG_SchemaKnownOk;
  }

  if( db->nSchemaLock==0 ){
    for(i=0; i<db->nDb; i++){
      if( DbHasProperty(db, i, DB_ResetWanted) ){
        sqlite3SchemaClear(db->aDb[i].pSchema);
        sqlite3SchemaClearOrDisconnect(db, i);
      }
    }
  }
}

/*
** Erase all schema information from all attached databases (including
** "main" and "temp") for a single database connection.
*/
void sqlite3ResetAllSchemasOfConnection(sqlite3 *db){
  int i;
  sqlite3BtreeEnterAll(db);
  for(i=0; i<db->nDb; i++){
  for(i=0; i<db->nDb; i=(i?i+1:2)){
    Db *pDb = &db->aDb[i];
    if( pDb->pSchema ){
      if( db->nSchemaLock==0 ){
        sqlite3SchemaClear(pDb->pSchema);
        sqlite3SchemaClearOrDisconnect(db, i);
      }else{
        DbSetProperty(db, i, DB_ResetWanted);
      }
    }
  }
  sqlite3SchemaClear(db->aDb[1].pSchema);
  db->mDbFlags &= ~(DBFLAG_SchemaChange|DBFLAG_SchemaKnownOk);
  sqlite3VtabUnlockList(db);
  sqlite3BtreeLeaveAll(db);
  if( db->nSchemaLock==0 ){
    sqlite3CollapseDatabaseArray(db);
  }
}

  ** it does. The exception is if the statement being parsed was passed
  ** to an sqlite3_declare_vtab() call. In that case only the column names
  ** and types will be used, so there is no need to test for namespace
  ** collisions.
  */
  if( !IN_SPECIAL_PARSE ){
    char *zDb = db->aDb[iDb].zDbSName;
    if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
    if( !IsSharedSchema(db) && SQLITE_OK!=sqlite3ReadSchema(pParse) ){
      goto begin_table_error;
    }
    pTable = sqlite3FindTable(db, zName, zDb);
    if( pTable ){
      if( !noErr ){
        sqlite3ErrorMsg(pParse, "%s %T already exists",
                        (IsView(pTable)? "view" : "table"), pName);

          pDb->zDbSName
        );
      }
    }
#endif

    /* Reparse everything to update our internal data structures */
    sqlite3VdbeAddParseSchemaOp(v, iDb,
    sqlite3VdbeAddParseSchemaOp(pParse, iDb,
           sqlite3MPrintf(db, "tbl_name='%q' AND type!='trigger'", p->zName),0);

    /* Test for cycles in generated columns and illegal expressions
    ** in CHECK constraints and in DEFAULT clauses. */
    if( p->tabFlags & TF_HasGenerated ){
      sqlite3VdbeAddOp4(v, OP_SqlExec, 0x0001, 0, 0,
             sqlite3MPrintf(db, "SELECT*FROM\"%w\".\"%w\"",

  if( db->mallocFailed ){
    goto exit_drop_table;
  }
  assert( pParse->nErr==0 );
  assert( pName->nSrc==1 );
  assert( pName->a[0].fg.fixedSchema==0 );
  assert( pName->a[0].fg.isSubquery==0 );
  if( sqlite3ReadSchema(pParse) ) goto exit_drop_table;
  if( !IsSharedSchema(db) && sqlite3ReadSchema(pParse) ) goto exit_drop_table;
  if( noErr ) db->suppressErr++;
  assert( isView==0 || isView==LOCATE_VIEW );
  pTab = sqlite3LocateTableItem(pParse, isView, &pName->a[0]);
  if( noErr ) db->suppressErr--;

  if( pTab==0 ){
    if( noErr ){
      sqlite3CodeVerifyNamedSchema(pParse, pName->a[0].u4.zDatabase);
      sqlite3ForceNotReadOnly(pParse);
    }
    goto exit_drop_table;
  }
  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
  assert( iDb>=0 && iDb<db->nDb );
  sqlite3SchemaWritable(pParse, iDb);

  /* If pTab is a virtual table, call ViewGetColumnNames() to ensure
  ** it is initialized.
  */
  if( IsVirtual(pTab) && sqlite3ViewGetColumnNames(pParse, pTab) ){
    goto exit_drop_table;
  }

  if( pParse->nErr ){
    goto exit_create_index;
  }
  assert( db->mallocFailed==0 );
  if( IN_DECLARE_VTAB && idxType!=SQLITE_IDXTYPE_PRIMARYKEY ){
    goto exit_create_index;
  }
  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
  if( !IsSharedSchema(db) && SQLITE_OK!=sqlite3ReadSchema(pParse) ){
    goto exit_create_index;
  }
  if( sqlite3HasExplicitNulls(pParse, pList) ){
    goto exit_create_index;
  }

  /*

      /* Fill the index with data and reparse the schema. Code an OP_Expire
      ** to invalidate all pre-compiled statements.
      */
      if( pTblName ){
        sqlite3RefillIndex(pParse, pIndex, iMem);
        sqlite3ChangeCookie(pParse, iDb);
        sqlite3VdbeAddParseSchemaOp(v, iDb,
        sqlite3VdbeAddParseSchemaOp(pParse, iDb,
            sqlite3MPrintf(db, "name='%q' AND type='index'", pIndex->zName), 0);
        sqlite3VdbeAddOp2(v, OP_Expire, 0, 1);
      }

      sqlite3VdbeJumpHere(v, (int)pIndex->tnum);
    }
  }

  }
  if( pIndex->idxType!=SQLITE_IDXTYPE_APPDEF ){
    sqlite3ErrorMsg(pParse, "index associated with UNIQUE "
      "or PRIMARY KEY constraint cannot be dropped", 0);
    goto exit_drop_index;
  }
  iDb = sqlite3SchemaToIndex(db, pIndex->pSchema);
  sqlite3SchemaWritable(pParse, iDb);
#ifndef SQLITE_OMIT_AUTHORIZATION
  {
    int code = SQLITE_DROP_INDEX;
    Table *pTab = pIndex->pTable;
    const char *zDb = db->aDb[iDb].zDbSName;
    const char *zTab = SCHEMA_TABLE(iDb);
    if( sqlite3AuthCheck(pParse, SQLITE_DELETE, zTab, 0, zDb) ){

**
** This file contains functions used to access the internal hash tables
** of user defined functions and collation sequences.
*/

#include "sqliteInt.h"

/*
** Connections opened with the SQLITE_OPEN_SHARED_SCHEMA flag specified
** may use SchemaPool objects for any database that is not the temp db
** (iDb==1). For such databases (type "struct Db") there are three states
** the Schema/SchemaPool object may be in.
**
**   1) pSPool==0, pSchema points to an empty object allocated by
**      sqlite3_malloc(). DB_SchemaLoaded flag is clear.
**
**   2) pSPool!=0, pSchema points to a populated object owned by the
**      SchemaPool. DB_SchemaLoaded flag is set.
**
**   3) pSPool!=0, pSchema points to the SchemaPool's static object
**      (SchemaPool.sSchema).
*/
struct SchemaPool {
  int nRef;                       /* Number of pointers to this object */
  int nDelete;                    /* Schema objects deleted by ReleaseAll() */
  u64 cksum;                      /* Checksum for this Schema contents */
  Schema *pSchema;                /* Linked list of Schema objects */
  Schema sSchema;                 /* The single dummy schema object */
  SchemaPool *pNext;              /* Next element in schemaPoolList */
};

#ifdef SQLITE_ENABLE_SHARED_SCHEMA
#ifdef SQLITE_DEBUG
static void assert_schema_state_ok(sqlite3 *db){
  if( IsSharedSchema(db) && db->eOpenState!=SQLITE_STATE_ZOMBIE ){
    int i;
    for(i=0; i<db->nDb; i++){
      if( i!=1 ){
        Db *pDb = &db->aDb[i];
        Btree *pBt = pDb->pBt;
        if( pBt==0 ) continue;
        assert( sqlite3BtreeSchema(pBt, 0, 0)==0 );
        assert( pDb->pSchema );
        if( pDb->pSPool ){
          if( DbHasProperty(db, i, DB_SchemaLoaded)==0 ){
            assert( pDb->pSchema->tblHash.count==0 );
            assert( pDb->pSchema==&pDb->pSPool->sSchema );
          }else{
            assert( pDb->pSchema!=&pDb->pSPool->sSchema );
          }
        }else{
          assert( DbHasProperty(db, i, DB_SchemaLoaded)==0 );
          assert( pDb->pSchema->tblHash.count==0 );
          assert( pDb->pSchema!=&pDb->pSPool->sSchema );
        }
      }
    }
  }
}
#else
# define assert_schema_state_ok(x)
#endif
#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */

/*
** Invoke the 'collation needed' callback to request a collation sequence
** in the encoding enc of name zName, length nName.
*/
static void callCollNeeded(sqlite3 *db, int enc, const char *zName){
  assert( !db->xCollNeeded || !db->xCollNeeded16 );
  if( db->xCollNeeded ){

  if( pSchema->schemaFlags & DB_SchemaLoaded ){
    pSchema->iGeneration++;
  }
  pSchema->schemaFlags &= ~(DB_SchemaLoaded|DB_ResetWanted);
}

/*
** If this database was opened with the SQLITE_OPEN_SHARED_SCHEMA flag
** and iDb!=1, then disconnect from the schema-pool associated with
** database iDb. Otherwise, clear the Schema object belonging to
** database iDb. 
**
** If an OOM error occurs while disconnecting from a schema-pool, 
** the db->mallocFailed flag is set.
*/
void sqlite3SchemaClearOrDisconnect(sqlite3 *db, int iDb){
  Db *pDb = &db->aDb[iDb];
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  if( IsSharedSchema(db) && iDb!=1 && pDb->pSPool ){
    sqlite3SchemaDisconnect(db, iDb, 1);
  }else
#endif
  {
    sqlite3SchemaClear(pDb->pSchema);
  }
}
** Find and return the schema associated with a BTree.  Create
** a new one if necessary.

#ifdef SQLITE_ENABLE_SHARED_SCHEMA
/*
** Global linked list of SchemaPool objects. Read and write access must
** be protected by the SQLITE_MUTEX_STATIC_MASTER mutex.
*/
static SchemaPool *SQLITE_WSD schemaPoolList = 0;

#ifdef SQLITE_TEST
/*
** Return a pointer to the head of the linked list of SchemaPool objects.
** This is used by the virtual table in file test_schemapool.c.
*/
SchemaPool *sqlite3SchemaPoolList(void){ return schemaPoolList; }
#endif

/*
** Database handle db was opened with the SHARED_SCHEMA flag, and database
** iDb is currently connected to a schema-pool. When this function is called,
** (*pnByte) is set to nInit plus the amount of memory used to store a 
** single instance of the Schema objects managed by the schema-pool.
** This function adjusts (*pnByte) sot hat it is set to nInit plus
** (nSchema/nRef) of the amount of memory used by a single Schema object,
** where nSchema is the number of Schema objects allocated by this pool,
** and nRef is the number of connections to the schema-pool.
*/
void sqlite3SchemaAdjustUsed(sqlite3 *db, int iDb, int nInit, int *pnByte){
  SchemaPool *pSPool = db->aDb[iDb].pSPool;
  int nSchema = 0;
  Schema *p;
  sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
  for(p=pSPool->pSchema; p; p=p->pNext){
    nSchema++;
  }
  *pnByte = nInit + ((*pnByte - nInit) * nSchema) / pSPool->nRef;
  sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
}

/*
** Check that the schema of db iDb is writable (either because it is the 
** temp db schema or because the db handle was opened without
** SQLITE_OPEN_SHARED_SCHEMA). If so, do nothing. Otherwise, leave an 
** error in the Parse object.
*/
void sqlite3SchemaWritable(Parse *pParse, int iDb){
  if( iDb!=1 && IsSharedSchema(pParse->db) && IN_DECLARE_VTAB==0 ){
    sqlite3ErrorMsg(pParse, "attempt to modify read-only schema");
  }
}

/*
** The schema object passed as the only argument was allocated using
** sqlite3_malloc() and then populated using the usual mechanism. This
** function frees both the Schema object and its contents.
*/
static void schemaDelete(Schema *pSchema){
  sqlite3SchemaClear((void*)pSchema);
  sqlite3_free(pSchema);
}

/*
** When this function is called, the database connection Db must be
** using a schema-pool (Db.pSPool!=0) and must currently have Db.pSchema
** set to point to a populated schema object checked out from the 
** schema-pool. It is also assumed that the STATIC_MASTER mutex is held.
** This function returns the Schema object to the schema-pool and sets
** Db.pSchema to point to the schema-pool's static, empty, Schema object.
*/
static void schemaRelease(sqlite3 *db, Db *pDb){
  Schema *pRelease = pDb->pSchema;
  SchemaPool *pSPool = pDb->pSPool;

  assert( pDb->pSchema->iGeneration==pSPool->sSchema.iGeneration );
  pDb->pSchema = &pSPool->sSchema;

  assert( pDb->pSPool && pRelease );
  assert( pRelease->schemaFlags & DB_SchemaLoaded );
  assert( (pDb->pSchema->schemaFlags & DB_SchemaLoaded)==0 );
  assert( sqlite3_mutex_held(sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER)) );

  /* If the DBFLAG_FreeSchema flag is set and the database connection holds
  ** at least one other copy of the schema being released, delete it instead
  ** of returning it to the schema-pool.  */
  if( db->mDbFlags & DBFLAG_FreeSchema ){
    int i;
    for(i=0; i<db->nDb; i++){
      Db *p = &db->aDb[i];
      if( p!=pDb && p->pSchema!=&pSPool->sSchema && pDb->pSPool==p->pSPool ){
        pSPool->nDelete++;
        schemaDelete(pRelease);
        return;
      }
    }
  }

  pRelease->pNext = pDb->pSPool->pSchema;
  pDb->pSPool->pSchema = pRelease;
}

/*
** The schema for database iDb of database handle db, which was opened
** with SQLITE_OPEN_SHARED_SCHEMA, has just been parsed. This function either
** finds a matching SchemaPool object on the global list (schemaPoolList) or
** else allocates a new one and sets the Db.pSPool variable accordingly.
**
** SQLITE_OK is returned if no error occurs, or an SQLite error code 
** (SQLITE_NOMEM) otherwise.
*/
int sqlite3SchemaConnect(sqlite3 *db, int iDb, u64 cksum){
  Schema *pSchema = db->aDb[iDb].pSchema;
  SchemaPool *p;

  assert( pSchema && iDb!=1 && db->aDb[iDb].pSPool==0 );

  sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );

  /* Search for a matching SchemaPool object */
  for(p=schemaPoolList; p; p=p->pNext){
    if( p->cksum==cksum && p->sSchema.schema_cookie==pSchema->schema_cookie ){
      break;
    }
  }
  if( !p ){
    /* No SchemaPool object found. Allocate a new one. */
    p = (SchemaPool*)sqlite3_malloc(sizeof(SchemaPool));
    if( p ){
      memset(p, 0, sizeof(SchemaPool));
      p->cksum = cksum;
      p->pNext = schemaPoolList;
      schemaPoolList = p;

      p->sSchema.schema_cookie = pSchema->schema_cookie;
      p->sSchema.iGeneration = pSchema->iGeneration;
      p->sSchema.file_format = pSchema->file_format;
      p->sSchema.enc = pSchema->enc;
      p->sSchema.cache_size = pSchema->cache_size;
    }
  }

  if( p ) p->nRef++;

  /* If the SchemaPool contains one or more free schemas at the moment, 
  ** delete one of them. */
  if( p && p->pSchema ){
    Schema *pDel = p->pSchema;
    p->pSchema = pDel->pNext;
    schemaDelete(pDel);
  }

  sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );

  db->aDb[iDb].pSPool = p;
  return (p ? SQLITE_OK : SQLITE_NOMEM);
}

/*
** If parameter iDb is 1 (the temp db), or if connection handle db was not
** opened with the SQLITE_OPEN_SHARED_SCHEMA flag, this function is a no-op.
** Otherwise, it disconnects from the schema-pool associated with database
** iDb, assuming it is connected.
**
** If parameter bNew is true, then Db.pSchema is set to point to a new, empty,
** Schema object obtained from sqlite3_malloc(). Or, if bNew is false, then
** Db.pSchema is set to NULL before returning.
**
** If the bNew parameter is true, then this function may allocate memory. 
** If the allocation attempt fails, then SQLITE_NOMEM is returned and the
** schema-pool is not disconnected from. Or, if no OOM error occurs, 
** SQLITE_OK is returned.
*/
int sqlite3SchemaDisconnect(sqlite3 *db, int iDb, int bNew){
  int rc = SQLITE_OK;
  if( IsSharedSchema(db) ){
    Db *pDb = &db->aDb[iDb];
    SchemaPool *pSPool = pDb->pSPool;
    assert_schema_state_ok(db);
    assert( pDb->pSchema );

    if( pSPool==0 ){
      assert( pDb->pVTable==0 );
      assert( bNew==0 );
      schemaDelete(pDb->pSchema);
      pDb->pSchema = 0;
    }else{
      VTable *p;
      VTable *pNext;
      for(p=pDb->pVTable; p; p=pNext){
        pNext = p->pNext;
        sqlite3VtabUnlock(p);
      }
      pDb->pVTable = 0;
      sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
      if( DbHasProperty(db, iDb, DB_SchemaLoaded) ){
        schemaRelease(db, pDb);
      }
      if( bNew ){
        Schema *pNew = sqlite3SchemaGet(db, 0);
        if( pNew==0 ){
          rc = SQLITE_NOMEM;
        }else{
          pDb->pSchema = pNew;
        }
      }
      if( rc==SQLITE_OK ){
        assert( pSPool->nRef>=1 );
        pDb->pSPool = 0;
        pSPool->nRef--;
        if( pSPool->nRef<=0 ){
          SchemaPool **pp;
          while( pSPool->pSchema ){
            Schema *pNext = pSPool->pSchema->pNext;
            schemaDelete(pSPool->pSchema);
            pSPool->pSchema = pNext;
          }
          for(pp=&schemaPoolList; (*pp)!=pSPool; pp=&((*pp)->pNext));
          *pp = pSPool->pNext;
          sqlite3_free(pSPool);
        }
      }
      sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
    }
  }
  return rc;
}

/*
** Extract and return a pointer to a schema object from the SchemaPool passed
** as the only argument, if one is available. If one is not available, return
** NULL.
*/
Schema *sqlite3SchemaExtract(SchemaPool *pSPool){
  Schema *pRet = 0;
  sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
  if( pSPool->pSchema ){
    pRet = pSPool->pSchema;
    pSPool->pSchema = pRet->pNext;
    pRet->pNext = 0;
  }
  sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
  return pRet;
}

/*
** Return all sharable schemas held by database handle db back to their
** respective schema-pools. Db.pSchema variables are left pointing to
** the static, empty, Schema object owned by each schema-pool.
*/
void sqlite3SchemaReleaseAll(sqlite3 *db){
  int i;
  assert_schema_state_ok(db);
  sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
  for(i=0; i<db->nDb; i++){
    if( i!=1 ){
      Db *pDb = &db->aDb[i];
      if( pDb->pSPool && DbHasProperty(db,i,DB_SchemaLoaded) ){
        schemaRelease(db, pDb);
      }
    }
  }
  db->mDbFlags &= ~DBFLAG_FreeSchema;
  sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
}

/*
** Release any sharable schema held by connection iDb of database handle
** db. Db.pSchema is left pointing to the static, empty, Schema object
** owned by the schema-pool.
*/
void sqlite3SchemaRelease(sqlite3 *db, int iDb){
  Db *pDb = &db->aDb[iDb];
  assert( iDb!=1 );
  assert_schema_state_ok(db);
  sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
  schemaRelease(db, pDb);
  sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
}

#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */

/*
** In most cases, this function finds and returns the schema associated 
** with BTree handle pBt, creating a new one if necessary. However, if
** the database handle was opened with the SQLITE_OPEN_SHARED_SCHEMA flag
** specified, a new, empty, Schema object in memory obtained by 
** sqlite3_malloc() is always returned.
*/
Schema *sqlite3SchemaGet(sqlite3 *db, Btree *pBt){
  Schema * p;
  if( pBt ){
    p = (Schema *)sqlite3BtreeSchema(pBt, sizeof(Schema), sqlite3SchemaClear);
  Schema *p;
  if( pBt && IsSharedSchema(db)==0 ){
    p = (Schema*)sqlite3BtreeSchema(pBt, sizeof(Schema), sqlite3SchemaClear);
  }else{
    p = (Schema *)sqlite3DbMallocZero(0, sizeof(Schema));
    p = (Schema*)sqlite3DbMallocZero(0, sizeof(Schema));
  }
  if( !p ){
    sqlite3OomFault(db);
  }else if ( 0==p->file_format ){
    sqlite3HashInit(&p->tblHash);
    sqlite3HashInit(&p->idxHash);
    sqlite3HashInit(&p->trigHash);
    sqlite3HashInit(&p->fkeyHash);
    p->enc = SQLITE_UTF8;
  }
  return p;
}

    Schema *pSchema = db->aDb[i].pSchema;
    if( pSchema ){
      for(p=sqliteHashFirst(&pSchema->tblHash); p; p=sqliteHashNext(p)){
        Table *pTab = (Table *)sqliteHashData(p);
        if( IsVirtual(pTab) ) sqlite3VtabDisconnect(db, pTab);
      }
    }
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
    if( IsSharedSchema(db) && i!=1 ){
      VTable *pVTable;
      VTable *pNext;
      for(pVTable=db->aDb[i].pVTable; pVTable; pVTable=pNext){
        pNext = pVTable->pNext;
        sqlite3VtabUnlock(pVTable);
      }
      db->aDb[i].pVTable = 0;
    }
#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
  }
  for(p=sqliteHashFirst(&db->aModule); p; p=sqliteHashNext(p)){
    Module *pMod = (Module *)sqliteHashData(p);
    if( pMod->pEpoTab ){
      sqlite3VtabDisconnect(db, pMod->pEpoTab);
    }
  }

  /* Close all database connections */
  for(j=0; j<db->nDb; j++){
    struct Db *pDb = &db->aDb[j];
    if( pDb->pBt ){
      sqlite3BtreeClose(pDb->pBt);
      pDb->pBt = 0;
      if( j!=1 ){
        (void)sqlite3SchemaDisconnect(db, j, 0);
        pDb->pSchema = 0;
      }
    }
  }
  /* Clear the TEMP schema separately and last */
  if( db->aDb[1].pSchema ){
    sqlite3SchemaClear(db->aDb[1].pSchema);

  const char *zColumnName,    /* Column name */
  char const **pzDataType,    /* OUTPUT: Declared data type */
  char const **pzCollSeq,     /* OUTPUT: Collation sequence name */
  int *pNotNull,              /* OUTPUT: True if NOT NULL constraint exists */
  int *pPrimaryKey,           /* OUTPUT: True if column part of PK */
  int *pAutoinc               /* OUTPUT: True if column is auto-increment */
){
  int rc;
  int rc = SQLITE_OK;
  char *zErrMsg = 0;
  Table *pTab = 0;
  Column *pCol = 0;
  int iCol = 0;
  char const *zDataType = 0;
  char const *zCollSeq = 0;
  int notnull = 0;
  int primarykey = 0;
  int autoinc = 0;

  int bUnlock;

#ifdef SQLITE_ENABLE_API_ARMOR
  if( !sqlite3SafetyCheckOk(db) || zTableName==0 ){
    return SQLITE_MISUSE_BKPT;
  }
#endif

  /* Ensure the database schema has been loaded */
  sqlite3_mutex_enter(db->mutex);
  bUnlock = sqlite3LockReusableSchema(db);
  sqlite3BtreeEnterAll(db);
  if( IsSharedSchema(db)==0 ){
  rc = sqlite3Init(db, &zErrMsg);
    rc = sqlite3Init(db, &zErrMsg);
  if( SQLITE_OK!=rc ){
    goto error_out;
  }

  /* Locate the table in question */
  if( rc==SQLITE_OK ){
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
    Parse sParse;                   /* Fake Parse object for FindTable */
    Parse *pSaved = db->pParse;
    memset(&sParse, 0, sizeof(sParse));
    db->pParse = &sParse;
#endif
  pTab = sqlite3FindTable(db, zTableName, zDbName);
    pTab = sqlite3FindTable(db, zTableName, zDbName);
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
    sqlite3_free(sParse.zErrMsg);
    rc = sParse.rc;
    db->pParse = pSaved;
#endif
  }
  if( SQLITE_OK!=rc ) goto error_out;

  if( !pTab || IsView(pTab) ){
    pTab = 0;
    goto error_out;
  }

  /* Find the column for which info is requested */
  if( zColumnName==0 ){

    zErrMsg = sqlite3MPrintf(db, "no such table column: %s.%s", zTableName,
        zColumnName);
    rc = SQLITE_ERROR;
  }
  sqlite3ErrorWithMsg(db, rc, (zErrMsg?"%s":0), zErrMsg);
  sqlite3DbFree(db, zErrMsg);
  rc = sqlite3ApiExit(db, rc);
  sqlite3UnlockReusableSchema(db, bUnlock);
  sqlite3_mutex_leave(db->mutex);
  return rc;
}

/*
** Sleep for a little while.  Return the amount of time slept.
*/

  /* If argument zPath is a NULL pointer, this function is required to open
  ** a temporary file. Use this buffer to store the file name in.
  */
  char *zTmpname = 0; /* For temporary filename, if necessary. */

  int rc = SQLITE_OK;            /* Function Return Code */
#if !defined(NDEBUG) || SQLITE_OS_WINCE
  int eType = flags&0x0FFF00;  /* Type of file to open */
  int eType = flags&0x0FFF00;    /* Type of file to open */
#endif

  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
  int isDelete     = (flags & SQLITE_OPEN_DELETEONCLOSE);
  int isCreate     = (flags & SQLITE_OPEN_CREATE);
  int isReadonly   = (flags & SQLITE_OPEN_READONLY);
  int isReadWrite  = (flags & SQLITE_OPEN_READWRITE);

  }
  p = zName - 4 - sizeof(Pager*);
  assert( EIGHT_BYTE_ALIGNMENT(p) );
  pPager = *(Pager**)p;
  return pPager->fd;
}


#ifdef SQLITE_ENABLE_READONLY_WALJOURNAL
/*
** This is used by a read-only database connection in cases where there
** is a hot journal which cannot be rolled back, but the hot journal was
** created by an aborted "PRAGMA journal_mode = wal" statement. In this
** case we can proceed, but must set bytes 18 and 19 of page 1 of the
** db file to indicate that this is not a wal mode database.
*/
static int getPageOneNoWal(
  Pager *pPager,      /* The pager open on the database file */
  Pgno pgno,          /* Page number to fetch */
  DbPage **ppPage,    /* Write a pointer to the page here */
  int flags           /* PAGER_GET_XXX flags */
){
  int rc = SQLITE_OK;

  assert( pgno==1 );
  assert( pPager->readOnly );
  assert( !isOpen(pPager->jfd) );

  rc = getPageNormal(pPager, pgno, ppPage, flags);
  if( rc==SQLITE_OK ){
    int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL;
    u8 *aPg = (u8*)(*ppPage)->pData;
    u8 aHdr[28];
    rc = sqlite3OsOpen(pPager->pVfs, pPager->zJournal, pPager->jfd, f, &f);
    if( rc==SQLITE_OK ){
      rc = sqlite3OsRead(pPager->jfd, (void*)aHdr, sizeof(aHdr), 0);
    }
    if( rc==SQLITE_OK ){
      u32 off = sqlite3Get4byte(&aHdr[20]);
      rc = sqlite3OsRead(pPager->jfd, (void*)aPg, pPager->pageSize, off+4);
    }
    sqlite3OsClose(pPager->jfd);
  }
  setGetterMethod(pPager);
  return rc;
}
#endif /* SQLITE_ENABLE_READONLY_WALJOURNAL */

/*
** This function is called after a potentially hot journal has been opened
** to inspect its contents and determine whether or not it really is a
** hot journal. The journal is not a hot journal in two cases:
**
**   * The first byte of the journal is 0x00, or, 
**
**   * The connection is opened read-only, the journal consist of page 1
**     of the db only, and the contents of page 1 differs from the contents
**     of the db only in bytes 18 and 19 (the wal mode setting).
**
** If the journal is not hot, then output variable (*pbHot) is set to 0
** before this function returns. Otherwise, if the journal is hot, (*pbHot)
** is set to 1.
*/
static int checkHotJournal(Pager *pPager, int *pbHot){
  char aHdr[28];
  int rc = SQLITE_OK;

  *pbHot = 1;
  rc = sqlite3OsRead(pPager->jfd, (void *)aHdr, sizeof(aHdr), 0);
  if( rc==SQLITE_OK ){
    if( aHdr[0]==0 ){
      *pbHot = 0;
    }
#ifdef SQLITE_ENABLE_READONLY_WALJOURNAL
    else if( pPager->readOnly ){
      u32 nPg = sqlite3Get4byte(&aHdr[8]);
      u32 off = sqlite3Get4byte(&aHdr[20]);
      u32 pgsz = sqlite3Get4byte(&aHdr[24]);

      if( nPg==0xFFFFFFFF ){
        i64 sz = 0;
        rc = sqlite3OsFileSize(pPager->jfd, &sz);
        nPg = ((sz-off) / pgsz);
      }
      if( nPg==1 ){
        u8 *a1 = 0;
        a1 = sqlite3_malloc(pgsz*2);
        if( a1==0 ){
          rc = SQLITE_NOMEM_BKPT;
        }else{
          u8 *a2 = &a1[pgsz];
          rc = sqlite3OsRead(pPager->jfd, a1, pgsz, off+4);
          if( rc==SQLITE_OK ){
            rc = sqlite3OsRead(pPager->fd, a2, pgsz, 0);
            memcpy(&a2[18], &a1[18], 2);
            memcpy(&a2[24], &a1[24], 4);
            memcpy(&a2[92], &a1[92], 8);
#ifdef SQLITE_ENABLE_ZIPVFS
            memcpy(&a2[176], &a1[176], 4);
#endif
          }
          if( rc==SQLITE_OK && memcmp(a1, a2, pgsz)==0 ){
            *pbHot = 0;
            pPager->xGet = getPageOneNoWal;
          }
          sqlite3_free(a1);
        }
      }
    }
#endif /* SQLITE_ENABLE_READONLY_WALJOURNAL */
  }
  if( rc==SQLITE_IOERR_SHORT_READ ){
    rc = SQLITE_OK;
  }
  return rc;
}

/*
** This function is called after transitioning from PAGER_UNLOCK to
** PAGER_SHARED state. It tests if there is a hot journal present in
** the file-system for the given pager. A hot journal is one that
** needs to be played back. According to this function, a hot-journal
** file exists if the following criteria are met:

          ** it can be ignored.
          */
          if( !jrnlOpen ){
            int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL;
            rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f);
          }
          if( rc==SQLITE_OK ){
            u8 first = 0;
            rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0);
            if( rc==SQLITE_IOERR_SHORT_READ ){
              rc = SQLITE_OK;
            rc = checkHotJournal(pPager, pExists);
            }
            if( !jrnlOpen ){
              sqlite3OsClose(pPager->jfd);
            }
            *pExists = (first!=0);
          }else if( rc==SQLITE_CANTOPEN ){
            /* If we cannot open the rollback journal file in order to see if
            ** it has a zero header, that might be due to an I/O error, or
            ** it might be due to the race condition described above and in
            ** ticket #3883.  Either way, assume that the journal is hot.
            ** This might be a false positive.  But if it is, then the
            ** automatic journal playback and recovery mechanism will deal

  }

 failed:
  if( rc!=SQLITE_OK ){
    assert( !MEMDB );
    pager_unlock(pPager);
    assert( pPager->eState==PAGER_OPEN );
#ifdef SQLITE_ENABLE_READONLY_WALJOURNAL
    testcase( pPager->xGet==getPageOneNoWal );
    setGetterMethod(pPager);
#endif /* SQLITE_ENABLE_READONLY_WALJOURNAL */
  }else{
    pPager->eState = PAGER_READER;
    pPager->hasHeldSharedLock = 1;
  }
  return rc;
}

){
  UNUSED_PARAMETER(pgno);
  UNUSED_PARAMETER(flags);
  assert( pPager->errCode!=SQLITE_OK );
  *ppPage = 0;
  return pPager->errCode;
}


/* Dispatch all page fetch requests to the appropriate getter method.
*/
int sqlite3PagerGet(
  Pager *pPager,      /* The pager open on the database file */
  Pgno pgno,          /* Page number to fetch */
  DbPage **ppPage,    /* Write a pointer to the page here */

        sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
      }else{
        int rc = SQLITE_OK;
        int state = pPager->eState;
        assert( state==PAGER_OPEN || state==PAGER_READER );
        if( state==PAGER_OPEN ){
          rc = sqlite3PagerSharedLock(pPager);

#ifdef SQLITE_ENABLE_READONLY_WALJOURNAL
          /* If this is a read-only connection, and there is a hot-journal
          ** created by "PRAGMA journal_mode = wal" in the file-system, then
          ** the Pager.xGet method may have been set to getPageOneNoWal. Call
          ** setGetterMethod() here to ensure it is set properly.  */
          testcase( pPager->xGet==getPageOneNoWal );
          setGetterMethod(pPager);
#endif /* SQLITE_ENABLE_READONLY_WALJOURNAL */
        }
        if( pPager->eState==PAGER_READER ){
          assert( rc==SQLITE_OK );
          rc = pagerLockDb(pPager, RESERVED_LOCK);
        }
        if( rc==SQLITE_OK ){
          sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);

    /* IMP: R-43042-22504 No error messages are generated if an
    ** unknown pragma is issued. */
    goto pragma_out;
  }

  /* Make sure the database schema is loaded if the pragma requires that */
  if( (pPragma->mPragFlg & PragFlg_NeedSchema)!=0 ){
    if( IsSharedSchema(db) && (zDb || (pPragma->mPragFlg & PragFlg_OneSchema)) ){
      assert( iDb>=0 && iDb<db->nDb );
      pParse->rc = sqlite3SchemaLoad(db, iDb, 0, &pParse->zErrMsg);
      if( pParse->rc ) goto pragma_out;
    }else{
    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
      if( sqlite3ReadSchema(pParse) ) goto pragma_out;
    }
  }

  /* Register the result column names for pragmas that return results */
  if( (pPragma->mPragFlg & PragFlg_NoColumns)==0
   && ((pPragma->mPragFlg & PragFlg_NoColumns1)==0 || zRight==0)
  ){
    setPragmaResultColumnNames(v, pPragma);

  ** the schema-version is potentially dangerous and may lead to program
  ** crashes or database corruption. Use with caution!
  **
  ** The user-version is not used internally by SQLite. It may be used by
  ** applications for any purpose.
  */
  case PragTyp_HEADER_VALUE: {
    int iCookie = pPragma->iArg;  /* Which cookie to read or write */
    int iCookie;                  /* Which cookie to read or write */
    iCookie = pPragma->iArg & PRAGMA_HEADER_VALUE_MASK;     
    sqlite3VdbeUsesBtree(v, iDb);
    if( zRight && (pPragma->mPragFlg & PragFlg_ReadOnly)==0 ){
    if( zRight && (pPragma->iArg & PRAGMA_HEADER_VALUE_READONLY)==0 ){
      /* Write the specified cookie value */
      static const VdbeOpList setCookie[] = {
        { OP_Transaction,    0,  1,  0},    /* 0 */
        { OP_SetCookie,      0,  0,  0},    /* 1 */
      };
      VdbeOp *aOp;
      sqlite3VdbeVerifyNoMallocRequired(v, ArraySize(setCookie));

        "error in %s %s after %s: %s", azObj[0], azObj[1], 
        azAlterType[(pData->mInitFlags&INITFLAG_AlterMask)-1], 
        zExtra
    );
    pData->rc = SQLITE_ERROR;
  }else if( db->flags & SQLITE_WriteSchema ){
    pData->rc = SQLITE_CORRUPT_BKPT;
  }else if( IsSharedSchema(db) 
         && 0==sqlite3StrNICmp(zExtra, "malformed database schema", 17)
  ){
    pData->rc = SQLITE_CORRUPT_BKPT;
    *pData->pzErrMsg = sqlite3DbStrDup(db, zExtra);
  }else{
    char *z;
    const char *zObj = azObj[1] ? azObj[1] : "?";
    z = sqlite3MPrintf(db, "malformed database schema (%s)", zObj);
    if( zExtra && zExtra[0] ) z = sqlite3MPrintf(db, "%z - %s", z, zExtra);
    *pData->pzErrMsg = z;
    pData->rc = SQLITE_CORRUPT_BKPT;
  }
}

#ifdef SQLITE_ENABLE_SHARED_SCHEMA
/*
** Update the Schema.cksum checksum to account for the database object
** specified by the three arguments following the first.
*/
static void schemaUpdateChecksum(
  InitData *pData,                /* Schema parse context */
  const char *zName,              /* Name of new database object */
  const char *zRoot,              /* Root page of new database object */
  const char *zSql                /* SQL used to create new database object */
){
  int i;
  u64 cksum = pData->cksum;
  if( zName ){
    for(i=0; zName[i]; i++) cksum += (cksum<<3) + zName[i];
  }
  if( zRoot ) for(i=0; zRoot[i]; i++) cksum += (cksum<<3) + zRoot[i];
  if( zSql ) for(i=0; zSql[i]; i++) cksum += (cksum<<3) + zSql[i];
  pData->cksum = cksum;
}
#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */

/*
** Check to see if any sibling index (another index on the same table)
** of pIndex has the same root page number, and if it does, return true.
** This would indicate a corrupt schema.
*/
int sqlite3IndexHasDuplicateRootPage(Index *pIndex){
  Index *p;
  for(p=pIndex->pTable->pIndex; p; p=p->pNext){
    if( p->tnum==pIndex->tnum && p!=pIndex ) return 1;
  }
  return 0;
}

/* forward declaration */
static int sqlite3Prepare(
  sqlite3 *db,              /* Database handle. */
  const char *zSql,         /* UTF-8 encoded SQL statement. */
  int nBytes,               /* Length of zSql in bytes. */
  u32 prepFlags,            /* Zero or more SQLITE_PREPARE_* flags */
  Vdbe *pReprepare,         /* VM being reprepared */
  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
  const char **pzTail       /* OUT: End of parsed string */
);
static int sqlite3LockAndPrepare(
  sqlite3 *db,              /* Database handle. */
  const char *zSql,         /* UTF-8 encoded SQL statement. */
  int nBytes,               /* Length of zSql in bytes. */
  u32 prepFlags,            /* Zero or more SQLITE_PREPARE_* flags */
  Vdbe *pReprepare,         /* VM being reprepared */
  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
  const char **pzTail       /* OUT: End of parsed string */

      if( sqlite3Config.bExtraSchemaChecks ){
        corruptSchema(pData, argv, "invalid rootpage");
      }
    }
    db->init.orphanTrigger = 0;
    db->init.azInit = (const char**)argv;
    pStmt = 0;
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
    TESTONLY(rcp = ) sqlite3LockAndPrepare(db, argv[4], -1, 0, 0, &pStmt, 0);
#else
    TESTONLY(rcp = ) sqlite3Prepare(db, argv[4], -1, 0, 0, &pStmt, 0);
#endif
    rc = db->errCode;
    assert( (rc&0xFF)==(rcp&0xFF) );
    db->init.iDb = saved_iDb;
    /* assert( saved_iDb==0 || (db->mDbFlags & DBFLAG_Vacuum)!=0 ); */
    if( SQLITE_OK!=rc ){
      if( db->init.orphanTrigger ){
        assert( iDb==1 );
      }else{
        if( rc > pData->rc ) pData->rc = rc;
        if( rc==SQLITE_NOMEM ){
          sqlite3OomFault(db);
        }else if( rc!=SQLITE_INTERRUPT && (rc&0xFF)!=SQLITE_LOCKED ){
        }else if( rc!=SQLITE_INTERRUPT && (rc&0xFF)!=SQLITE_LOCKED
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
               && (rc&0xFF)!=SQLITE_IOERR
#endif
        ){
          corruptSchema(pData, argv, sqlite3_errmsg(db));
        }
      }
    }
    db->init.azInit = sqlite3StdType; /* Any array of string ptrs will do */
    sqlite3_finalize(pStmt);
  }else if( argv[1]==0 || (argv[4]!=0 && argv[4][0]!=0) ){

     || sqlite3IndexHasDuplicateRootPage(pIndex)
    ){
      if( sqlite3Config.bExtraSchemaChecks ){
        corruptSchema(pData, argv, "invalid rootpage");
      }
    }
  }

#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  if( IsSharedSchema(db) && iDb!=1 ){
    schemaUpdateChecksum(pData, argv[0], argv[1], argv[2]);
  }
#endif
  return 0;
}

/*
** Attempt to read the database schema and initialize internal
** data structures for a single database file.  The index of the
** database file is given by iDb.  iDb==0 is used for the main

  InitData initData;
  const char *zSchemaTabName;
  int openedTransaction = 0;
  int mask = ((db->mDbFlags & DBFLAG_EncodingFixed) | ~DBFLAG_EncodingFixed);

  assert( (db->mDbFlags & DBFLAG_SchemaKnownOk)==0 );
  assert( iDb>=0 && iDb<db->nDb );
  assert( db->aDb[iDb].pSchema );
  assert( db->aDb[iDb].pSchema || (IsSharedSchema(db) && iDb!=1) );
  assert( sqlite3_mutex_held(db->mutex) );
  assert( iDb==1 || sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );

  pDb = &db->aDb[iDb];
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  assert( pDb->pSPool==0 || IsSharedSchema(db) );
  if( pDb->pSPool ){
    /* See if there is a free schema object in the schema-pool. If not,
    ** disconnect from said schema pool and continue. This function will
    ** connect to a (possibly different) schema-pool before returning. */
    Schema *pNew = sqlite3SchemaExtract(pDb->pSPool);
    if( pNew ){
      pDb->pSchema = pNew;
      return SQLITE_OK;
    }
    rc = sqlite3SchemaDisconnect(db, iDb, 1);
    if( rc!=SQLITE_OK ) goto error_out;
    assert( pDb->pSchema && pDb->pSPool==0 );
  }
#endif

  db->init.busy = 1;

  /* Construct the in-memory representation schema tables (sqlite_schema or
  ** sqlite_temp_schema) by invoking the parser directly.  The appropriate
  ** table name will be inserted automatically by the parser so we can just
  ** use the abbreviation "x" here.  The parser will also automatically tag

  azArg[5] = 0;
  initData.db = db;
  initData.iDb = iDb;
  initData.rc = SQLITE_OK;
  initData.pzErrMsg = pzErrMsg;
  initData.mInitFlags = mFlags;
  initData.nInitRow = 0;
  initData.cksum = 0;
  initData.mxPage = 0;
  sqlite3InitCallback(&initData, 5, (char **)azArg, 0);
  db->mDbFlags &= mask;
  if( initData.rc ){
    rc = initData.rc;
    goto error_out;
  }

  /* Create a cursor to hold the database open
  */
  pDb = &db->aDb[iDb];
  if( pDb->pBt==0 ){
    assert( iDb==1 );
    DbSetProperty(db, 1, DB_SchemaLoaded);
    rc = SQLITE_OK;
    goto error_out;
  }

    **
    ** The primary purpose of this is to allow access to the sqlite_schema
    ** table even when its contents have been corrupted.
    */
    DbSetProperty(db, iDb, DB_SchemaLoaded);
    rc = SQLITE_OK;
  }

  if( rc==SQLITE_OK && iDb!=1 && IsSharedSchema(db) ){
    rc = sqlite3SchemaConnect(db, iDb, initData.cksum);
  }

  /* Jump here for an error that occurs after successfully allocating
  ** curMain and calling sqlite3BtreeEnter(). For an error that occurs
  ** before that point, jump to error_out.
  */
initone_error_out:
  if( openedTransaction ){

    }
    sqlite3ResetOneSchema(db, iDb);
  }
  db->init.busy = 0;
  return rc;
}


#ifdef SQLITE_ENABLE_SHARED_SCHEMA
/*
** If this is a SHARED_SCHEMA connection and the DBFLAG_SchemaInUse flag
** is not currently set, set it and return non-zero. Otherwise, return 0.
*/
int sqlite3LockReusableSchema(sqlite3 *db){
  if( IsSharedSchema(db) && (db->mDbFlags & DBFLAG_SchemaInuse)==0 ){
    db->mDbFlags |= DBFLAG_SchemaInuse;
    return 1;
  }
  return 0;
}
#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */

#ifdef SQLITE_ENABLE_SHARED_SCHEMA
/*
** This function is a no-op for non-SHARED_SCHEMA connections, or if bRelease
** is zero. Otherwise, clear the DBFLAG_SchemaInuse flag and release all
** schema references currently held.
*/
void sqlite3UnlockReusableSchema(sqlite3 *db, int bRelease){
  if( bRelease ){
    db->mDbFlags &= ~DBFLAG_SchemaInuse;
    sqlite3SchemaReleaseAll(db);
  }
}
#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */

/*
** Initialize all database files - the main database file, the file
** used to store temporary tables, and any additional database files
** created using ATTACH statements.  Return a success code.  If an
** error occurs, write an error message into *pzErrMsg.
**
** After a database is initialized, the DB_SchemaLoaded bit is set
** bit is set in the flags field of the Db structure. 
*/
int sqlite3Init(sqlite3 *db, char **pzErrMsg){
  int rc = SQLITE_OK;
  int bReleaseSchema;
  int i, rc;
  int i;
  int commit_internal = !(db->mDbFlags&DBFLAG_SchemaChange);

  bReleaseSchema = sqlite3LockReusableSchema(db);
  
  assert( sqlite3_mutex_held(db->mutex) );
  assert( sqlite3BtreeHoldsMutex(db->aDb[0].pBt) );
  assert( db->init.busy==0 );
  ENC(db) = SCHEMA_ENC(db);
  assert( db->nDb>0 );
  /* Do the main schema first */
  if( !DbHasProperty(db, 0, DB_SchemaLoaded) ){
    rc = sqlite3InitOne(db, 0, pzErrMsg, 0);
    if( rc ) return rc;
  }
  /* All other schemas after the main schema. The "temp" schema must be last */
  for(i=db->nDb-1; i>0; i--){
  for(i=db->nDb-1; rc==SQLITE_OK && i>0; i--){
    assert( i==1 || sqlite3BtreeHoldsMutex(db->aDb[i].pBt) );
    if( !DbHasProperty(db, i, DB_SchemaLoaded) ){
      rc = sqlite3InitOne(db, i, pzErrMsg, 0);
      if( rc ) return rc;
    }
  }
  if( commit_internal ){
  if( rc==SQLITE_OK && commit_internal ){
    sqlite3CommitInternalChanges(db);
  }
  sqlite3UnlockReusableSchema(db, bReleaseSchema);
  return SQLITE_OK;
  return rc;
}

/*
** This routine is a no-op if the database schema is already initialized.
** Otherwise, the schema is loaded. An error code is returned.
*/
int sqlite3ReadSchema(Parse *pParse){
  int rc = SQLITE_OK;
  sqlite3 *db = pParse->db;
  assert( sqlite3_mutex_held(db->mutex) );
  if( !db->init.busy ){
    db->mDbFlags |= DBFLAG_FreeSchema;      /* For sharable-schema mode */
    rc = sqlite3Init(db, &pParse->zErrMsg);
    if( rc!=SQLITE_OK ){
      pParse->rc = rc;
      pParse->nErr++;
    }else if( db->noSharedCache ){
    }else if( db->noSharedCache && !IsSharedSchema(db) ){
      db->mDbFlags |= DBFLAG_SchemaKnownOk;
    }
  }
  return rc;
}

  assert( pParse->checkSchema );
  assert( sqlite3_mutex_held(db->mutex) );
  for(iDb=0; iDb<db->nDb; iDb++){
    int openedTransaction = 0;         /* True if a transaction is opened */
    Btree *pBt = db->aDb[iDb].pBt;     /* Btree database to read cookie from */
    if( pBt==0 ) continue;

#ifdef SQLITE_ENABLE_SHARED_SCHEMA
    if( IsSharedSchema(db) && iDb!=1 && db->aDb[iDb].pSPool==0 ) continue;
#endif

    /* If there is not already a read-only (or read-write) transaction opened
    ** on the b-tree database, open one now. If a transaction is opened, it 
    ** will be closed immediately after reading the meta-value. */
    if( sqlite3BtreeTxnState(pBt)==SQLITE_TXN_NONE ){
      rc = sqlite3BtreeBeginTrans(pBt, 0, 0);
      if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){

  u32 prepFlags,            /* Zero or more SQLITE_PREPARE_* flags */
  Vdbe *pOld,               /* VM being reprepared */
  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
  const char **pzTail       /* OUT: End of parsed string */
){
  int rc;
  int cnt = 0;
  int bReleaseSchema = 0;

#ifdef SQLITE_ENABLE_API_ARMOR
  if( ppStmt==0 ) return SQLITE_MISUSE_BKPT;
#endif
  *ppStmt = 0;
  if( !sqlite3SafetyCheckOk(db)||zSql==0 ){
    return SQLITE_MISUSE_BKPT;
  }
  sqlite3_mutex_enter(db->mutex);
  bReleaseSchema = sqlite3LockReusableSchema(db);
  sqlite3BtreeEnterAll(db);
  do{
    /* Make multiple attempts to compile the SQL, until it either succeeds
    ** or encounters a permanent error.  A schema problem after one schema
    ** reset is considered a permanent error. */
    rc = sqlite3Prepare(db, zSql, nBytes, prepFlags, pOld, ppStmt, pzTail);
    assert( rc==SQLITE_OK || *ppStmt==0 );
    if( rc==SQLITE_OK || db->mallocFailed ) break;
  }while( (rc==SQLITE_ERROR_RETRY && (cnt++)<SQLITE_MAX_PREPARE_RETRY)
       || (rc==SQLITE_SCHEMA && (sqlite3ResetOneSchema(db,-1), cnt++)==0) );

  sqlite3BtreeLeaveAll(db);

  sqlite3UnlockReusableSchema(db, bReleaseSchema);

  rc = sqlite3ApiExit(db, rc);
  assert( (rc&db->errMask)==rc );
  db->busyHandler.nBusy = 0;
  sqlite3_mutex_leave(db->mutex);
  assert( rc==SQLITE_OK || (*ppStmt)==0 );
  return rc;
}

#define AUTOEQP_off      0           /* Automatic EXPLAIN QUERY PLAN is off */
#define AUTOEQP_on       1           /* Automatic EQP is on */
#define AUTOEQP_trigger  2           /* On and also show plans for triggers */
#define AUTOEQP_full     3           /* Show full EXPLAIN */

/* Allowed values for ShellState.openMode
*/
#define SHELL_OPEN_UNSPEC      0      /* No open-mode specified */
#define SHELL_OPEN_NORMAL      1      /* Normal database file */
#define SHELL_OPEN_APPENDVFS   2      /* Use appendvfs */
#define SHELL_OPEN_ZIPFILE     3      /* Use the zipfile virtual table */
#define SHELL_OPEN_READONLY    4      /* Open a normal database read-only */
#define SHELL_OPEN_DESERIALIZE 5      /* Open using sqlite3_deserialize() */
#define SHELL_OPEN_HEXDB       6      /* Use "dbtotxt" output as data source */
#define SHELL_OPEN_UNSPEC       0     /* No open-mode specified */
#define SHELL_OPEN_NORMAL       1     /* Normal database file */
#define SHELL_OPEN_APPENDVFS    2     /* Use appendvfs */
#define SHELL_OPEN_ZIPFILE      3     /* Use the zipfile virtual table */
#define SHELL_OPEN_READONLY     4     /* Open a normal database read-only */
#define SHELL_OPEN_DESERIALIZE  5     /* Open using sqlite3_deserialize() */
#define SHELL_OPEN_HEXDB        6     /* Use "dbtotxt" output as data source */
#define SHELL_OPEN_SHAREDSCHEMA 7     /* Open for schema reuse */

/* Allowed values for ShellState.eTraceType
*/
#define SHELL_TRACE_PLAIN      0      /* Show input SQL text */
#define SHELL_TRACE_EXPANDED   1      /* Show expanded SQL text */
#define SHELL_TRACE_NORMALIZED 2      /* Show normalized SQL text */

  "    Options:",
  "      --schema              Also hash the sqlite_schema table",
  "      --sha3-224            Use the sha3-224 algorithm",
  "      --sha3-256            Use the sha3-256 algorithm (default)",
  "      --sha3-384            Use the sha3-384 algorithm",
  "      --sha3-512            Use the sha3-512 algorithm",
  "    Any other argument is a LIKE pattern for tables to hash",
#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_ENABLE_DBPAGE_VTAB)
  ".shared-schema CMD DB1 DB2 ...",
  "    Commands:",
  "       check                Determine if DB1, DB2, etc have identical schemas",
  "       fix                  Attempt to make DB1, DB2, etc compatible",
#endif
#if !defined(SQLITE_NOHAVE_SYSTEM) && !defined(SQLITE_SHELL_FIDDLE)
  ".shell CMD ARGS...       Run CMD ARGS... in a system shell",
#endif
  ".show                    Show the current values for various settings",
  ".stats ?ARG?             Show stats or turn stats on or off",
  "   off                      Turn off automatic stat display",
  "   on                       Turn on automatic stat display",

        sqlite3_open(":memory:", &p->db);
        break;
      }
      case SHELL_OPEN_READONLY: {
        sqlite3_open_v2(zDbFilename, &p->db,
            SQLITE_OPEN_READONLY|p->openFlags, 0);
        break;
      }
      case SHELL_OPEN_SHAREDSCHEMA: {
        sqlite3_open_v2(p->pAuxDb->zDbFilename, &p->db,
          SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_SHARED_SCHEMA,0);
        break;
      }
      case SHELL_OPEN_UNSPEC:
      case SHELL_OPEN_NORMAL: {
        sqlite3_open_v2(zDbFilename, &p->db,
           SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|p->openFlags, 0);
        break;
      }

  sqlite3_free(cmd.zSrcTable);

  return rc;
}
/* End of the ".archive" or ".ar" command logic
*******************************************************************************/
#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_HAVE_ZLIB) */

/*
** If (*pRc) is not SQLITE_OK when this function is called, it is a no-op.
** Otherwise, the SQL statement or statements in zSql are executed using
** database connection db and the error code written to *pRc before
** this function returns.
*/
static void shellExec(sqlite3 *db, int *pRc, const char *zSql){
  int rc = *pRc;
  if( rc==SQLITE_OK ){
    char *zErr = 0;
    rc = sqlite3_exec(db, zSql, 0, 0, &zErr);
    if( rc!=SQLITE_OK ){
      sqlite3_fprintf(stderr, "SQL error: %s\n", zErr);
    }
    sqlite3_free(zErr);
    *pRc = rc;
  }
}
#if SQLITE_SHELL_HAVE_RECOVER


/*
** Like shellExec(), except that zFmt is a printf() style format string.
*/
static void shellExecPrintf(sqlite3 *db, int *pRc, const char *zFmt, ...){
  char *z = 0;
  if( *pRc==SQLITE_OK ){
    va_list ap;
    va_start(ap, zFmt);
    z = sqlite3_vmprintf(zFmt, ap);
    va_end(ap);
    if( z==0 ){
      *pRc = SQLITE_NOMEM;
    }else{
      shellExec(db, pRc, z);
    }
    sqlite3_free(z);
  }
}

static int sharedSchemaFix(ShellState *pState, const char *zDb){
  int rc = SQLITE_OK;
  i64 iLast = 0;
  int iCookie = 0;
  int iAutoVacuum = 0;
  sqlite3_stmt *pStmt = 0;

  shellExecPrintf(pState->db, &rc, "ATTACH '%q' AS _shared_schema_tmp", zDb);
  shellExecPrintf(pState->db, &rc, "PRAGMA writable_schema = 1");
  shellExecPrintf(pState->db, &rc, "BEGIN");
  shellPreparePrintf(pState->db, &rc, &pStmt, 
      "SELECT max(rowid) FROM _shared_schema_tmp.sqlite_master"
  );
  sqlite3_step(pStmt);
  iLast = sqlite3_column_int64(pStmt, 0);
  shellFinalize(&rc, pStmt);
  shellPreparePrintf(pState->db, &rc, &pStmt,
      "INSERT INTO _shared_schema_tmp.sqlite_master SELECT "
      "  type, name, tbl_name, ("
      "    SELECT rootpage FROM _shared_schema_tmp.sqlite_master WHERE "
      "      type IS o.type AND name IS o.name AND rowid<=?"
      "  ), sql FROM main.sqlite_master AS o"
  );
  sqlite3_bind_int64(pStmt, 1, iLast);
  sqlite3_step(pStmt);
  shellFinalize(&rc, pStmt);

  shellExecPrintf(pState->db, &rc,
      "DELETE FROM _shared_schema_tmp.sqlite_master WHERE rowid<=%lld",
      iLast
  );
  shellExecPrintf(pState->db, &rc, "COMMIT");
  sqlite3_exec(pState->db, "PRAGMA writable_schema = 0", 0, 0, 0);

  /* Copy the auto-vacuum setting from main to the target db */
  shellPreparePrintf(pState->db, &rc, &pStmt, "PRAGMA main.auto_vacuum");
  sqlite3_step(pStmt);
  iAutoVacuum = sqlite3_column_int(pStmt, 0);
  shellFinalize(&rc, pStmt);
  shellExecPrintf(pState->db, &rc, 
      "PRAGMA _shared_schema_tmp.auto_vacuum = %d", iAutoVacuum
  );

  /* Vacuum the db in order to standardize the rootpage numbers. */
  shellExecPrintf(pState->db, &rc, "VACUUM _shared_schema_tmp");

  /* Set the schema-cookie value to the same as database "main" */
  shellPreparePrintf(pState->db, &rc, &pStmt, "PRAGMA main.schema_version");
  sqlite3_step(pStmt);
  iCookie = sqlite3_column_int(pStmt, 0);
  shellFinalize(&rc, pStmt);
  shellExecPrintf(pState->db, &rc, 
      "PRAGMA _shared_schema_tmp.schema_version = %d", iCookie
  );

  sqlite3_exec(pState->db, "DETACH _shared_schema_tmp", 0, 0, 0);
  return rc;
}

static int sharedSchemaCheck(ShellState *pState, const char *zDb, int *peFix){
  int rc = SQLITE_OK;
  int bFailed = 0;
  sqlite3_stmt *pStmt = 0;

  if( peFix ) *peFix = 0;
  shellExecPrintf(pState->db, &rc, "ATTACH '%q' AS _shared_schema_tmp", zDb);

  /* Check if this database has the same set of objects as the current db */
  shellPreparePrintf(pState->db, &rc, &pStmt, 
    "SELECT type, name FROM _shared_schema_tmp.sqlite_master AS o "
    "WHERE NOT EXISTS ("
    "  SELECT 1 FROM main.sqlite_master "
    "    WHERE name IS o.name AND type IS o.type"
    ")"
    " UNION ALL "
    "SELECT type, name FROM main.sqlite_master AS o "
    "WHERE NOT EXISTS ("
    "  SELECT 1 FROM _shared_schema_tmp.sqlite_master "
    "    WHERE name IS o.name AND type IS o.type"
    ")"
  );
  if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
    sqlite3_fprintf(pState->out, "%s is NOT compatible (objects)\n", zDb);
    bFailed = 1;
  }
  shellFinalize(&rc, pStmt);

  /* Check if this database has the same set of SQL statements as the 
  ** current db. */
  if( bFailed==0 ){
    shellPreparePrintf(pState->db, &rc, &pStmt, 
        "SELECT 1 FROM _shared_schema_tmp.sqlite_master AS o "
        "WHERE sql IS NOT ("
        "  SELECT sql FROM main.sqlite_master "
        "    WHERE name IS o.name AND type IS o.type"
        ")"
    );
    if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
      sqlite3_fprintf(pState->out, "%s is NOT compatible (SQL)\n", zDb);
      bFailed = 1;
    }
    shellFinalize(&rc, pStmt);
  }

  /* Check if this database has the same set of root pages as the current 
  ** db. */
  if( bFailed==0 ){
    shellPreparePrintf(pState->db, &rc, &pStmt, 
        "SELECT 1 FROM _shared_schema_tmp.sqlite_master AS o "
        "WHERE rootpage IS NOT ("
        "  SELECT rootpage FROM main.sqlite_master "
        "    WHERE name IS o.name AND type IS o.type"
        ")"
    );
    if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
      if( peFix==0 ){
        sqlite3_fprintf(pState->out, "%s is NOT compatible (root pages)\n", zDb);
      }
      bFailed = 1;
      if( peFix ) *peFix = 1;
    }
    shellFinalize(&rc, pStmt);
  }

  if( bFailed==0 ){
    shellPreparePrintf(pState->db, &rc, &pStmt, 
        "SELECT 1 WHERE ("
        "  SELECT group_concat(rootpage || '.' || name || '.' || sql, '.') "
        "  FROM _shared_schema_tmp.sqlite_master"
        ") IS NOT ("
        "  SELECT group_concat(rootpage || '.' || name || '.' || sql, '.') "
        "  FROM main.sqlite_master"
        ")"
    );
    if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
      if( peFix==0 ){
        sqlite3_fprintf(pState->out, 
            "%s is NOT compatible (order of sqlite_master rows)\n", zDb
        );
      }
      bFailed = 1;
      if( peFix ) *peFix = 2;
    }
    shellFinalize(&rc, pStmt);
  }

  if( bFailed==0 ){
    int iMain = -1;
    int iNew = +1;
    shellPreparePrintf(pState->db, &rc, &pStmt, 
        "PRAGMA main.schema_version"
    );
    if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
      iMain = sqlite3_column_int(pStmt, 0);
    }
    shellFinalize(&rc, pStmt);
    shellPreparePrintf(pState->db, &rc, &pStmt, 
        "PRAGMA _shared_schema_tmp.schema_version"
    );
    if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
      iNew = sqlite3_column_int(pStmt, 0);
    }
    shellFinalize(&rc, pStmt);
    if( rc==SQLITE_OK && iMain!=iNew ){
      if( peFix==0 ){
        sqlite3_fprintf(pState->out, 
            "%s is NOT compatible (schema cookie)\n", zDb
        );
      }
      bFailed = 1;
      if( peFix ) *peFix = 3;
    }
  }

  if( rc==SQLITE_OK && bFailed==0 ){
    sqlite3_fprintf(pState->out, "%s is compatible\n", zDb);
  }

  sqlite3_exec(pState->db, "DETACH _shared_schema_tmp", 0, 0, 0);
  return rc;
}

/*
** .shared-schema check|fix DB1 DB2...
*/
static int sharedSchemaDotCommand(
  ShellState *pState,             /* Current shell tool state */
  char **azArg,                   /* Array of arguments passed to dot command */
  int nArg                        /* Number of entries in azArg[] */
){
  int rc = SQLITE_OK;
  int bFix = 0;                   /* Fix databases if possible */
  int n1;
  int i;
  if( nArg<3 ){
    goto shared_schema_usage;
  }

  n1 = (int)strlen(azArg[1]);
  if( n1>0 && n1<=3 && memcmp("fix", azArg[1], n1)==0 ){
    bFix = 1;
  }else if( n1==0 || n1>5 || memcmp("check", azArg[1], n1) ){
    goto shared_schema_usage;
  }

  for(i=2; rc==SQLITE_OK && i<nArg; i++){
    int eFix = 0;
    rc = sharedSchemaCheck(pState, azArg[i], bFix ? &eFix : 0);
    if( rc==SQLITE_OK && bFix && eFix ){
      sqlite3_fprintf(pState->out, "Fixing %s... ", azArg[i]);
      fflush(pState->out);
      rc = sharedSchemaFix(pState, azArg[i]);
      if( rc==SQLITE_OK ){
        rc = sharedSchemaCheck(pState, azArg[i], &eFix);
        if( rc==SQLITE_OK && eFix ){
          sqlite3_fprintf(pState->out, "VACUUMing main... ");
          fflush(pState->out);
          rc = sqlite3_exec(pState->db, "VACUUM main", 0, 0, 0);
          if( rc==SQLITE_OK ){
            rc = sharedSchemaCheck(pState, azArg[i], 0);
          }
        }
      }
    }
  }

  return rc;
 shared_schema_usage:
  sqlite3_fprintf(stderr, "usage: .shared-schema check|fix DB1 DB2...\n");
  return SQLITE_ERROR;
}

#if SQLITE_SHELL_HAVE_RECOVER
/*
** This function is used as a callback by the recover extension. Simply
** print the supplied SQL statement to stdout.
*/
static int recoverSqlCb(void *pCtx, const char *zSql){
  ShellState *pState = (ShellState*)pCtx;
  sqlite3_fprintf(pState->out, "%s;\n", zSql);

      }
      if( rc ) eputz(".sha3sum failed.\n");
      sqlite3_free(zRevText);
    }
#endif /* !defined(*_OMIT_SCHEMA_PRAGMAS) && !defined(*_OMIT_VIRTUALTABLE) */
    sqlite3_free(zSql);
  }else

#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_ENABLE_DBPAGE_VTAB)
  if( c=='s' && strncmp(azArg[0], "shared-schema", n)==0 ){
    open_db(p, 0);
    sharedSchemaDotCommand(p, azArg, nArg);
  }else
#endif

#if !defined(SQLITE_NOHAVE_SYSTEM) && !defined(SQLITE_SHELL_FIDDLE)
  if( c=='s'
   && (cli_strncmp(azArg[0], "shell", n)==0
       || cli_strncmp(azArg[0],"system",n)==0)
  ){
    char *zCmd;

    }else if( cli_strcmp(z,"-deserialize")==0 ){
      data.openMode = SHELL_OPEN_DESERIALIZE;
    }else if( cli_strcmp(z,"-maxsize")==0 && i+1<argc ){
      data.szMax = integerValue(argv[++i]);
#endif
    }else if( cli_strcmp(z,"-readonly")==0 ){
      data.openMode = SHELL_OPEN_READONLY;
    }else if( strcmp(z,"-sharedschema")==0 ){
      data.openMode = SHELL_OPEN_SHAREDSCHEMA;
    }else if( cli_strcmp(z,"-nofollow")==0 ){
      data.openFlags = SQLITE_OPEN_NOFOLLOW;
#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_HAVE_ZLIB)
    }else if( cli_strncmp(z, "-A",2)==0 ){
      /* All remaining command-line arguments are passed to the ".archive"
      ** command, so ignore them */
      break;

    }else if( cli_strcmp(z,"-deserialize")==0 ){
      data.openMode = SHELL_OPEN_DESERIALIZE;
    }else if( cli_strcmp(z,"-maxsize")==0 && i+1<argc ){
      data.szMax = integerValue(argv[++i]);
#endif
    }else if( cli_strcmp(z,"-readonly")==0 ){
      data.openMode = SHELL_OPEN_READONLY;
    }else if( strcmp(z,"-sharedschema")==0 ){
      data.openMode = SHELL_OPEN_SHAREDSCHEMA;
    }else if( cli_strcmp(z,"-nofollow")==0 ){
      data.openFlags |= SQLITE_OPEN_NOFOLLOW;
    }else if( cli_strcmp(z,"-ascii")==0 ){
      data.mode = MODE_Ascii;
      sqlite3_snprintf(sizeof(data.colSeparator), data.colSeparator,SEP_Unit);
      sqlite3_snprintf(sizeof(data.rowSeparator), data.rowSeparator,SEP_Record);
    }else if( cli_strcmp(z,"-tabs")==0 ){

#define SQLITE_OPEN_SHAREDCACHE      0x00020000  /* Ok for sqlite3_open_v2() */
#define SQLITE_OPEN_PRIVATECACHE     0x00040000  /* Ok for sqlite3_open_v2() */
#define SQLITE_OPEN_WAL              0x00080000  /* VFS only */
#define SQLITE_OPEN_NOFOLLOW         0x01000000  /* Ok for sqlite3_open_v2() */
#define SQLITE_OPEN_EXRESCODE        0x02000000  /* Extended result codes */

/* Reserved:                         0x00F00000 */
#define SQLITE_OPEN_SHARED_SCHEMA    0x01000000  /* Ok for sqlite3_open_v2() */

/* Legacy compatibility: */
#define SQLITE_OPEN_MASTER_JOURNAL   0x00004000  /* VFS only */


/*
** CAPI3REF: Device Characteristics
**
** The xDeviceCharacteristics method of the [sqlite3_io_methods]
** object returns an integer which is a vector of these
** bit values expressing I/O characteristics of the mass storage

typedef struct Column Column;
typedef struct Cte Cte;
typedef struct CteUse CteUse;
typedef struct Db Db;
typedef struct DbClientData DbClientData;
typedef struct DbFixer DbFixer;
typedef struct Schema Schema;
typedef struct SchemaPool SchemaPool;
typedef struct Expr Expr;
typedef struct ExprList ExprList;
typedef struct FKey FKey;
typedef struct FpDecode FpDecode;
typedef struct FuncDestructor FuncDestructor;
typedef struct FuncDef FuncDef;
typedef struct FuncDefHash FuncDefHash;

*/
struct Db {
  char *zDbSName;      /* Name of this database. (schema name, not filename) */
  Btree *pBt;          /* The B*Tree structure for this database file */
  u8 safety_level;     /* How aggressive at syncing data to disk */
  u8 bSyncSet;         /* True if "PRAGMA synchronous=N" has been run */
  Schema *pSchema;     /* Pointer to database schema (possibly shared) */
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  SchemaPool *pSPool;  /* For REUSE_SCHEMA mode */
  VTable *pVTable;     /* List of all VTable objects (REUSE_SCHEMA mode only) */
#endif
};

/*
** An instance of the following structure stores a database schema.
**
** Most Schema objects are associated with a Btree.  The exception is
** the Schema for the TEMP database (sqlite3.aDb[1]) which is free-standing.

  Hash trigHash;       /* All triggers indexed by name */
  Hash fkeyHash;       /* All foreign keys by referenced table name */
  Table *pSeqTab;      /* The sqlite_sequence table used by AUTOINCREMENT */
  u8 file_format;      /* Schema format version for this file */
  u8 enc;              /* Text encoding used by this database */
  u16 schemaFlags;     /* Flags associated with this schema */
  int cache_size;      /* Number of pages to use in the cache */
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  Schema *pNext;       /* Next Schema object SchemaPool (REUSE_SCHEMA) */
#endif
};

/*
** These macros can be used to test, set, or clear bits in the
** Db.pSchema->flags field.
*/
#define DbHasProperty(D,I,P)     (((D)->aDb[I].pSchema->schemaFlags&(P))==(P))

  sqlite3 *pUnlockConnection;           /* Connection to watch for unlock */
  void *pUnlockArg;                     /* Argument to xUnlockNotify */
  void (*xUnlockNotify)(void **, int);  /* Unlock notify callback */
  sqlite3 *pNextBlocked;        /* Next in list of all blocked connections */
#endif
};

#ifdef SQLITE_ENABLE_SHARED_SCHEMA
# define IsSharedSchema(db) (((db)->openFlags & SQLITE_OPEN_SHARED_SCHEMA)!=0)
#else
# define IsSharedSchema(db) 0
#endif

/*
** A macro to discover the encoding of a database.
*/
#define SCHEMA_ENC(db) ((db)->aDb[0].pSchema->enc)
#define ENC(db)        ((db)->enc)

/*

#define DBFLAG_PreferBuiltin  0x0002  /* Preference to built-in funcs */
#define DBFLAG_Vacuum         0x0004  /* Currently in a VACUUM */
#define DBFLAG_VacuumInto     0x0008  /* Currently running VACUUM INTO */
#define DBFLAG_SchemaKnownOk  0x0010  /* Schema is known to be valid */
#define DBFLAG_InternalFunc   0x0020  /* Allow use of internal functions */
#define DBFLAG_EncodingFixed  0x0040  /* No longer possible to change enc. */

#define DBFLAG_SchemaInuse    0x0080  /* Do not release sharable schemas */
#define DBFLAG_FreeSchema     0x0100  /* Free extra shared schemas on release */

/*
** Bits of the sqlite3.dbOptFlags field that are used by the
** sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS,...) interface to
** selectively disable various optimizations.
*/
#define SQLITE_QueryFlattener 0x00000001 /* Query flattening */
#define SQLITE_WindowFunc     0x00000002 /* Use xInverse for window functions */

  sqlite3_vtab *pVtab;      /* Pointer to vtab instance */
  int nRef;                 /* Number of pointers to this structure */
  u8 bConstraint;           /* True if constraints are supported */
  u8 bAllSchemas;           /* True if might use any attached schema */
  u8 eVtabRisk;             /* Riskiness of allowing hacker access */
  int iSavepoint;           /* Depth of the SAVEPOINT stack */
  VTable *pNext;            /* Next in linked list (see above) */
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  char *zName;              /* Table name (REUSE_SCHEMA mode) */
#endif
};

/* Allowed values for VTable.eVtabRisk
*/
#define SQLITE_VTABRISK_Low          0
#define SQLITE_VTABRISK_Normal       1
#define SQLITE_VTABRISK_High         2

  Expr *pWhen;            /* The WHEN clause of the expression (may be NULL) */
  IdList *pColumns;       /* If this is an UPDATE OF <column-list> trigger,
                             the <column-list> is stored here */
  Schema *pSchema;        /* Schema containing the trigger */
  Schema *pTabSchema;     /* Schema containing the table */
  TriggerStep *step_list; /* Link list of trigger program steps             */
  Trigger *pNext;         /* Next trigger associated with the table */
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  char *zTabSchema;       /* Temp triggers in IsSharedSchema() dbs only */
#endif
};

/*
** A trigger is either a BEFORE or an AFTER trigger.  The following constants
** determine which.
**
** If there are multiple triggers, you might of some BEFORE and some AFTER.

typedef struct {
  sqlite3 *db;        /* The database being initialized */
  char **pzErrMsg;    /* Error message stored here */
  int iDb;            /* 0 for main database.  1 for TEMP, 2.. for ATTACHed */
  int rc;             /* Result code stored here */
  u32 mInitFlags;     /* Flags controlling error messages */
  u32 nInitRow;       /* Number of rows processed */
  u64 cksum;          /* Schema checksum for REUSE_SCHEMA mode */
  Pgno mxPage;        /* Maximum page number.  0 for no limit. */
} InitData;

/*
** Allowed values for mInitFlags
*/
#define INITFLAG_AlterMask     0x0003  /* Types of ALTER */

int sqlite3FindDbName(sqlite3 *, const char *);
int sqlite3AnalysisLoad(sqlite3*,int iDB);
void sqlite3DeleteIndexSamples(sqlite3*,Index*);
void sqlite3DefaultRowEst(Index*);
void sqlite3RegisterLikeFunctions(sqlite3*, int);
int sqlite3IsLikeFunction(sqlite3*,Expr*,int*,char*);
void sqlite3SchemaClear(void *);
void sqlite3SchemaClearOrDisconnect(sqlite3*, int);

#ifdef SQLITE_ENABLE_SHARED_SCHEMA 
int sqlite3SchemaConnect(sqlite3*, int, u64);
int sqlite3SchemaDisconnect(sqlite3 *, int, int);
Schema *sqlite3SchemaExtract(SchemaPool*);
int sqlite3SchemaLoad(sqlite3*, int, int*, char**);
void sqlite3SchemaReleaseAll(sqlite3*);
void sqlite3SchemaRelease(sqlite3*, int);
void sqlite3SchemaAdjustUsed(sqlite3*, int, int, int*);
void sqlite3SchemaWritable(Parse*, int);
void sqlite3UnlockReusableSchema(sqlite3 *db, int bRelease);
int sqlite3LockReusableSchema(sqlite3 *db);
#else
# define sqlite3SchemaWritable(x,y)
# define sqlite3UnlockReusableSchema(x,y) (void)(y)
# define sqlite3LockReusableSchema(x) 0
# define sqlite3SchemaDisconnect(x,y,z) SQLITE_OK
# define sqlite3SchemaLoad(w,x,y,z) SQLITE_OK
# define sqlite3SchemaRelease(y,z)
# define sqlite3SchemaConnect(x,y,z) SQLITE_OK
#endif

Schema *sqlite3SchemaGet(sqlite3 *, Btree *);
int sqlite3SchemaToIndex(sqlite3 *db, Schema *);
KeyInfo *sqlite3KeyInfoAlloc(sqlite3*,int,int);
void sqlite3KeyInfoUnref(KeyInfo*);
KeyInfo *sqlite3KeyInfoRef(KeyInfo*);
KeyInfo *sqlite3KeyInfoOfIndex(Parse*, Index*);
KeyInfo *sqlite3KeyInfoFromExprList(Parse*, ExprList*, int, int);

    ** *pCurrent gets an accurate estimate of the amount of memory used
    ** to store the schema for all databases (main, temp, and any ATTACHed
    ** databases.  *pHighwater is set to zero.
    */
    case SQLITE_DBSTATUS_SCHEMA_USED: {
      int i;                      /* Used to iterate through schemas */
      int nByte = 0;              /* Used to accumulate return value */
      int bReleaseSchema;

      sqlite3BtreeEnterAll(db);
      bReleaseSchema = sqlite3LockReusableSchema(db);
      db->pnBytesFreed = &nByte;
      assert( db->lookaside.pEnd==db->lookaside.pTrueEnd );
      db->lookaside.pEnd = db->lookaside.pStart;
      for(i=0; i<db->nDb; i++){
        Schema *pSchema;
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
        int bUnload = 0;
        int nUsed = nByte;
        if( db->aDb[i].pSPool ){
          char *zDummy = 0;
          rc = sqlite3SchemaLoad(db, i, &bUnload, &zDummy);
          sqlite3_free(zDummy);
          if( rc ) break;
        }
#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
        Schema *pSchema = db->aDb[i].pSchema;
        pSchema = db->aDb[i].pSchema;
        if( ALWAYS(pSchema!=0) ){
          HashElem *p;

          nByte += sqlite3GlobalConfig.m.xRoundup(sizeof(HashElem)) * (
              pSchema->tblHash.count 
            + pSchema->trigHash.count
            + pSchema->idxHash.count

          for(p=sqliteHashFirst(&pSchema->trigHash); p; p=sqliteHashNext(p)){
            sqlite3DeleteTrigger(db, (Trigger*)sqliteHashData(p));
          }
          for(p=sqliteHashFirst(&pSchema->tblHash); p; p=sqliteHashNext(p)){
            sqlite3DeleteTable(db, (Table *)sqliteHashData(p));
          }
        }
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
        if( db->aDb[i].pSPool ){
          if( bUnload ) sqlite3SchemaRelease(db, i);
          sqlite3SchemaAdjustUsed(db, i, nUsed, &nByte);
      }
        }
#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
      }
      sqlite3UnlockReusableSchema(db, bReleaseSchema);
      db->pnBytesFreed = 0;
      db->lookaside.pEnd = db->lookaside.pTrueEnd;
      sqlite3BtreeLeaveAll(db);

      *pHighwater = 0;
      *pCurrent = nByte;
      break;

  Tcl_Interp *interp,
  Tcl_Obj *const*objv
){
  Tcl_WrongNumArgs(interp, 1, objv,
    "HANDLE ?FILENAME? ?-vfs VFSNAME? ?-readonly BOOLEAN? ?-create BOOLEAN?"
    " ?-nofollow BOOLEAN?"
    " ?-nomutex BOOLEAN? ?-fullmutex BOOLEAN? ?-uri BOOLEAN?"
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
    " ?-shared-schema BOOLEAN?"
#endif
  );
  return TCL_ERROR;
}

/*
**   sqlite3 DBNAME FILENAME ?-vfs VFSNAME? ?-key KEY? ?-readonly BOOLEAN?
**                           ?-create BOOLEAN? ?-nomutex BOOLEAN?

      int b;
      if( Tcl_GetBooleanFromObj(interp, objv[i], &b) ) return TCL_ERROR;
      if( b ){
        flags |= SQLITE_OPEN_URI;
      }else{
        flags &= ~SQLITE_OPEN_URI;
      }
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
    }else if( strcmp(zArg, "-shared-schema")==0 ){
      int b;
      if( Tcl_GetBooleanFromObj(interp, objv[i], &b) ) return TCL_ERROR;
      if( b ){
        flags |= SQLITE_OPEN_SHARED_SCHEMA;
      }else{
        flags &= ~SQLITE_OPEN_SHARED_SCHEMA;
      }
#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
    }else if( strcmp(zArg, "-translatefilename")==0 ){
      if( Tcl_GetBooleanFromObj(interp, objv[i], &bTranslateFileName) ){
        return TCL_ERROR;
      }
    }else{
      Tcl_AppendResult(interp, "unknown option: ", zArg, (char*)0);
      return TCL_ERROR;

#endif

#ifdef SQLITE_OMIT_PROGRESS_CALLBACK
  Tcl_SetVar2(interp, "sqlite_options", "progress", "0", TCL_GLOBAL_ONLY);
#else
  Tcl_SetVar2(interp, "sqlite_options", "progress", "1", TCL_GLOBAL_ONLY);
#endif

#ifdef SQLITE_ENABLE_READONLY_WALJOURNAL
  Tcl_SetVar2(
      interp, "sqlite_options", "readonly_waljournal", "1", TCL_GLOBAL_ONLY);
#else
  Tcl_SetVar2(
      interp, "sqlite_options", "readonly_waljournal", "0", TCL_GLOBAL_ONLY);
#endif

#ifdef SQLITE_OMIT_REINDEX
  Tcl_SetVar2(interp, "sqlite_options", "reindex", "0", TCL_GLOBAL_ONLY);
#else
  Tcl_SetVar2(interp, "sqlite_options", "reindex", "1", TCL_GLOBAL_ONLY);
#endif

#endif

#ifdef SQLITE_OMIT_WINDOWFUNC
  Tcl_SetVar2(interp, "sqlite_options", "windowfunc", "0", TCL_GLOBAL_ONLY);
#else
  Tcl_SetVar2(interp, "sqlite_options", "windowfunc", "1", TCL_GLOBAL_ONLY);
#endif

#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  Tcl_SetVar2(interp, "sqlite_options", "sharedschema", "1", TCL_GLOBAL_ONLY);
#else
  Tcl_SetVar2(interp, "sqlite_options", "sharedschema", "0", TCL_GLOBAL_ONLY);
#endif


#if !defined(SQLITE_ENABLE_SETLK_TIMEOUT)
  Tcl_SetVar2(interp, "sqlite_options", "setlk_timeout", "0", TCL_GLOBAL_ONLY);
#else
  Tcl_SetVar2(interp, "sqlite_options", "setlk_timeout", 
      STRINGVALUE(SQLITE_ENABLE_SETLK_TIMEOUT), TCL_GLOBAL_ONLY);
#endif

/*
** 2006 June 10
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing the virtual table interfaces.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
*/

/*
** None of this works unless we have virtual tables.
*/
#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_TEST)

#include "tclsqlite.h"

#ifdef SQLITE_ENABLE_SHARED_SCHEMA

#include "sqliteInt.h"

/* The code in this file defines a sqlite3 virtual-table module with
** the following schema.
*/
#define SCHEMAPOOL_SCHEMA \
"CREATE TABLE x("         \
"  cksum   INTEGER, "     \
"  nref    INTEGER, "     \
"  nschema INTEGER, "     \
"  ndelete INTEGER  "     \
")"

#define SCHEMAPOOL_NFIELD 4

typedef struct schemapool_vtab schemapool_vtab;
typedef struct schemapool_cursor schemapool_cursor;

/* A schema table object */
struct schemapool_vtab {
  sqlite3_vtab base;
};

/* A schema table cursor object */
struct schemapool_cursor {
  sqlite3_vtab_cursor base;
  sqlite3_int64 *aData;
  int iRow;
  int nRow;
};

/*
** Table destructor for the schema module.
*/
static int schemaPoolDestroy(sqlite3_vtab *pVtab){
  sqlite3_free(pVtab);
  return 0;
}

/*
** Table constructor for the schema module.
*/
static int schemaPoolCreate(
  sqlite3 *db,
  void *pAux,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  int rc = SQLITE_NOMEM;
  schemapool_vtab *pVtab = sqlite3_malloc(sizeof(schemapool_vtab));
  if( pVtab ){
    memset(pVtab, 0, sizeof(schemapool_vtab));
    rc = sqlite3_declare_vtab(db, SCHEMAPOOL_SCHEMA);
    if( rc!=SQLITE_OK ){
      sqlite3_free(pVtab);
      pVtab = 0;
    }
  }
  *ppVtab = (sqlite3_vtab *)pVtab;
  return rc;
}

/*
** Open a new cursor on the schema table.
*/
static int schemaPoolOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
  int rc = SQLITE_NOMEM;
  schemapool_cursor *pCur;
  pCur = sqlite3_malloc(sizeof(schemapool_cursor));
  if( pCur ){
    memset(pCur, 0, sizeof(schemapool_cursor));
    *ppCursor = (sqlite3_vtab_cursor*)pCur;
    rc = SQLITE_OK;
  }
  return rc;
}

/*
** Close a schema table cursor.
*/
static int schemaPoolClose(sqlite3_vtab_cursor *cur){
  schemapool_cursor *pCur = (schemapool_cursor*)cur;
  sqlite3_free(pCur->aData);
  sqlite3_free(pCur);
  return SQLITE_OK;
}

/*
** Retrieve a column of data.
*/
static int schemaPoolColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
  schemapool_cursor *pCur = (schemapool_cursor*)cur;
  assert( i==0 || i==1 || i==2 || i==3 );
  sqlite3_result_int64(ctx, pCur->aData[pCur->iRow*SCHEMAPOOL_NFIELD + i]);
  return SQLITE_OK;
}

/*
** Retrieve the current rowid.
*/
static int schemaPoolRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
  schemapool_cursor *pCur = (schemapool_cursor*)cur;
  *pRowid = pCur->iRow + 1;
  return SQLITE_OK;
}

static int schemaPoolEof(sqlite3_vtab_cursor *cur){
  schemapool_cursor *pCur = (schemapool_cursor*)cur;
  return pCur->iRow>=pCur->nRow;
}

/*
** Advance the cursor to the next row.
*/
static int schemaPoolNext(sqlite3_vtab_cursor *cur){
  schemapool_cursor *pCur = (schemapool_cursor*)cur;
  pCur->iRow++;
  return SQLITE_OK;
}

struct SchemaPool {
  int nRef;                       /* Number of pointers to this object */
  int nDelete;                    /* Schema objects deleted by ReleaseAll() */
  u64 cksum;                      /* Checksum for this Schema contents */
  Schema *pSchema;                /* Linked list of Schema objects */
  Schema sSchema;                 /* The single dummy schema object */
  SchemaPool *pNext;              /* Next element in schemaPoolList */
};
extern SchemaPool *sqlite3SchemaPoolList(void);

/*
** Reset a schemaPool table cursor.
*/
static int schemaPoolFilter(
  sqlite3_vtab_cursor *pVtabCursor, 
  int idxNum, const char *idxStr,
  int argc, sqlite3_value **argv
){
  SchemaPool *pSPool;
  schemapool_cursor *pCur = (schemapool_cursor*)pVtabCursor;

  sqlite3_free(pCur->aData);
  pCur->aData = 0;
  pCur->nRow = 0;
  pCur->iRow = 0;

  for(pSPool = sqlite3SchemaPoolList(); pSPool; pSPool=pSPool->pNext){
    pCur->nRow++;
  }

  if( pCur->nRow ){
    int iRow = 0;
    int nByte = SCHEMAPOOL_NFIELD * pCur->nRow * sizeof(i64);
    pCur->aData = (i64*)sqlite3_malloc(nByte);
    if( pCur->aData==0 ) return SQLITE_NOMEM;
    for(pSPool = sqlite3SchemaPoolList(); pSPool; pSPool=pSPool->pNext){
      Schema *p;
      i64 nSchema = 0;
      for(p=pSPool->pSchema; p; p=p->pNext){
        nSchema++;
      }
      pCur->aData[0 + iRow*SCHEMAPOOL_NFIELD] = pSPool->cksum;
      pCur->aData[1 + iRow*SCHEMAPOOL_NFIELD] = (i64)pSPool->nRef;
      pCur->aData[2 + iRow*SCHEMAPOOL_NFIELD] = nSchema;
      pCur->aData[3 + iRow*SCHEMAPOOL_NFIELD] = (i64)pSPool->nDelete;
      iRow++;
    }
  }

  return SQLITE_OK;
}

/*
** Analyse the WHERE condition.
*/
static int schemaPoolBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
  return SQLITE_OK;
}

/*
** A virtual table module that merely echos method calls into TCL
** variables.
*/
static sqlite3_module schemaPoolModule = {
  0,                           /* iVersion */
  schemaPoolCreate,
  schemaPoolCreate,
  schemaPoolBestIndex,
  schemaPoolDestroy,
  schemaPoolDestroy,
  schemaPoolOpen,              /* xOpen - open a cursor */
  schemaPoolClose,             /* xClose - close a cursor */
  schemaPoolFilter,            /* xFilter - configure scan constraints */
  schemaPoolNext,              /* xNext - advance a cursor */
  schemaPoolEof,               /* xEof */
  schemaPoolColumn,            /* xColumn - read data */
  schemaPoolRowid,             /* xRowid - read data */
  0,                           /* xUpdate */
  0,                           /* xBegin */
  0,                           /* xSync */
  0,                           /* xCommit */
  0,                           /* xRollback */
  0,                           /* xFindMethod */
  0,                           /* xRename */
};

/*
** Decode a pointer to an sqlite3 object.
*/
extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);

/*
** Register the schema virtual table module.
*/
static int SQLITE_TCLAPI register_schemapool_module(
  ClientData clientData, /* Not used */
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int objc,              /* Number of arguments */
  Tcl_Obj *CONST objv[]  /* Command arguments */
){
  sqlite3 *db;
  if( objc!=2 ){
    Tcl_WrongNumArgs(interp, 1, objv, "DB");
    return TCL_ERROR;
  }
  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
#ifndef SQLITE_OMIT_VIRTUALTABLE
  sqlite3_create_module(db, "schemapool", &schemaPoolModule, 0);
#endif
  return TCL_OK;
}

#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_TEST) */

/*
** Register commands with the TCL interpreter.
*/
int Sqlitetestschemapool_Init(Tcl_Interp *interp){
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  static struct {
     char *zName;
     Tcl_ObjCmdProc *xProc;
     void *clientData;
  } aObjCmd[] = {
     { "register_schemapool_module", register_schemapool_module, 0 },
  };
  int i;
  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
  }
#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
  return TCL_OK;
}

  extern int Sqlitetest_demovfs_Init(Tcl_Interp *);
  extern int Sqlitetest_func_Init(Tcl_Interp*);
  extern int Sqlitetest_hexio_Init(Tcl_Interp*);
  extern int Sqlitetest_init_Init(Tcl_Interp*);
  extern int Sqlitetest_malloc_Init(Tcl_Interp*);
  extern int Sqlitetest_mutex_Init(Tcl_Interp*);
  extern int Sqlitetestschema_Init(Tcl_Interp*);
  extern int Sqlitetestschemapool_Init(Tcl_Interp*);
  extern int Sqlitetestsse_Init(Tcl_Interp*);
  extern int Sqlitetesttclvar_Init(Tcl_Interp*);
  extern int Sqlitetestfs_Init(Tcl_Interp*);
  extern int SqlitetestThread_Init(Tcl_Interp*);
  extern int SqlitetestOnefile_Init();
  extern int SqlitetestOsinst_Init(Tcl_Interp*);
  extern int Sqlitetestbackup_Init(Tcl_Interp*);

  Sqlitetest_demovfs_Init(interp);
  Sqlitetest_func_Init(interp);
  Sqlitetest_hexio_Init(interp);
  Sqlitetest_init_Init(interp);
  Sqlitetest_malloc_Init(interp);
  Sqlitetest_mutex_Init(interp);
  Sqlitetestschema_Init(interp);
  Sqlitetestschemapool_Init(interp);
  Sqlitetesttclvar_Init(interp);
  Sqlitetestfs_Init(interp);
  SqlitetestThread_Init(interp);
  SqlitetestOnefile_Init();
  SqlitetestOsinst_Init(interp);
  Sqlitetestbackup_Init(interp);
  Sqlitetestintarray_Init(interp);

** that fire off of pTab.  The list will include any TEMP triggers on
** pTab as well as the triggers lised in pTab->pTrigger.
*/
Trigger *sqlite3TriggerList(Parse *pParse, Table *pTab){
  Schema *pTmpSchema;       /* Schema of the pTab table */
  Trigger *pList;           /* List of triggers to return */
  HashElem *p;              /* Loop variable for TEMP triggers */

#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  char *zSchema = 0;
  sqlite3 *db = pParse->db;
  if( IsSharedSchema(db) ){
    zSchema = db->aDb[sqlite3SchemaToIndex(db, pTab->pSchema)].zDbSName;
  }
#endif

  assert( pParse->disableTriggers==0 );
  pTmpSchema = pParse->db->aDb[1].pSchema;
  p = sqliteHashFirst(&pTmpSchema->trigHash);
  pList = pTab->pTrigger;
  while( p ){
    Trigger *pTrig = (Trigger *)sqliteHashData(p);

    int bSchemaMatch;
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
    if( zSchema ){
      /* Shared-schema */
      bSchemaMatch = (0==sqlite3StrICmp(pTrig->zTabSchema, zSchema));
    }else
#endif
    {
      /* Non-shared-schema */
    if( pTrig->pTabSchema==pTab->pSchema
      bSchemaMatch = (pTrig->pTabSchema==pTab->pSchema);
    }

    if( bSchemaMatch
     && pTrig->table
     && 0==sqlite3StrICmp(pTrig->table, pTab->zName)
     && (pTrig->pTabSchema!=pTmpSchema || pTrig->bReturning)
    ){
      pTrig->pNext = pList;
      pList = pTrig;
    }else if( pTrig->op==TK_RETURNING ){
#ifndef SQLITE_OMIT_VIRTUALTABLE
      assert( pParse->db->pVtabCtx==0 );
#endif
#endif 
      assert( pParse->bReturning );
      assert( !pParse->isCreate );
      assert( &(pParse->u1.d.pReturning->retTrig) == pTrig );
      pTrig->table = pTab->zName;
      pTrig->pTabSchema = pTab->pSchema;
      pTrig->pNext = pList;
      pList = pTrig;

  /* Build the Trigger object */
  pTrigger = (Trigger*)sqlite3DbMallocZero(db, sizeof(Trigger));
  if( pTrigger==0 ) goto trigger_cleanup;
  pTrigger->zName = zName;
  zName = 0;
  pTrigger->table = sqlite3DbStrDup(db, pTableName->a[0].zName);
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  if( IsSharedSchema(db) && iDb==1 ){
    int iTabDb = sqlite3SchemaToIndex(db, pTab->pSchema);
    pTrigger->zTabSchema = sqlite3DbStrDup(db, db->aDb[iTabDb].zDbSName);
  }
#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
  pTrigger->pSchema = db->aDb[iDb].pSchema;
  pTrigger->pTabSchema = pTab->pSchema;
  pTrigger->op = (u8)op;
  pTrigger->tr_tm = tr_tm==TK_BEFORE ? TRIGGER_BEFORE : TRIGGER_AFTER;
  if( IN_RENAME_OBJECT ){
    sqlite3RenameTokenRemap(pParse, pTrigger->table, pTableName->a[0].zName);
    pTrigger->pWhen = pWhen;

    sqlite3NestedParse(pParse,
       "INSERT INTO %Q." LEGACY_SCHEMA_TABLE
       " VALUES('trigger',%Q,%Q,0,'CREATE TRIGGER %q')",
       db->aDb[iDb].zDbSName, zName,
       pTrig->table, z);
    sqlite3DbFree(db, z);
    sqlite3ChangeCookie(pParse, iDb);
    sqlite3VdbeAddParseSchemaOp(v, iDb,
    sqlite3VdbeAddParseSchemaOp(pParse, iDb,
        sqlite3MPrintf(db, "type='trigger' AND name='%q'", zName), 0);
  }

  if( db->init.busy ){
    Trigger *pLink = pTrig;
    Hash *pHash = &db->aDb[iDb].pSchema->trigHash;
    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );

** Recursively delete a Trigger structure
*/
void sqlite3DeleteTrigger(sqlite3 *db, Trigger *pTrigger){
  if( pTrigger==0 || pTrigger->bReturning ) return;
  sqlite3DeleteTriggerStep(db, pTrigger->step_list);
  sqlite3DbFree(db, pTrigger->zName);
  sqlite3DbFree(db, pTrigger->table);
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  sqlite3DbFree(db, pTrigger->zTabSchema);
#endif
  sqlite3ExprDelete(db, pTrigger->pWhen);
  sqlite3IdListDelete(db, pTrigger->pColumns);
  sqlite3DbFree(db, pTrigger);
}

/*
** This function is called to drop a trigger from the database schema. 

  Table   *pTable;
  Vdbe *v;
  sqlite3 *db = pParse->db;
  int iDb;

  iDb = sqlite3SchemaToIndex(pParse->db, pTrigger->pSchema);
  assert( iDb>=0 && iDb<db->nDb );
  sqlite3SchemaWritable(pParse, iDb);
  pTable = tableOfTrigger(pTrigger);
  assert( (pTable && pTable->pSchema==pTrigger->pSchema) || iDb==1 );
#ifndef SQLITE_OMIT_AUTHORIZATION
  if( pTable ){
    int code = SQLITE_DROP_TRIGGER;
    const char *zDb = db->aDb[iDb].zDbSName;
    const char *zTab = SCHEMA_TABLE(iDb);

  Expr *pWhen = 0;            /* Duplicate of trigger WHEN expression */
  Vdbe *v;                    /* Temporary VM */
  NameContext sNC;            /* Name context for sub-vdbe */
  SubProgram *pProgram = 0;   /* Sub-vdbe for trigger program */
  int iEndTrigger = 0;        /* Label to jump to if WHEN is false */
  Parse sSubParse;            /* Parse context for sub-vdbe */

  assert( pTrigger->zName==0 || pTab==tableOfTrigger(pTrigger) );
  assert( pTrigger->zName==0 || IsSharedSchema(pParse->db)
      || pTab==tableOfTrigger(pTrigger)
  );
  assert( pTop->pVdbe );

  /* Allocate the TriggerPrg and SubProgram objects. To ensure that they
  ** are freed if an error occurs, link them into the Parse.pTriggerPrg 
  ** list of the top-level Parse object sooner rather than later.  */
  pPrg = sqlite3DbMallocZero(db, sizeof(TriggerPrg));
  if( !pPrg ) return 0;

  Trigger *pTrigger,   /* Trigger to code */
  Table *pTab,         /* The table trigger pTrigger is attached to */
  int orconf           /* ON CONFLICT algorithm. */
){
  Parse *pRoot = sqlite3ParseToplevel(pParse);
  TriggerPrg *pPrg;

  assert( pTrigger->zName==0 || pTab==tableOfTrigger(pTrigger) );
  assert( pTrigger->zName==0 || IsSharedSchema(pParse->db)
      || pTab==tableOfTrigger(pTrigger) 
  );

  /* It may be that this trigger has already been coded (or is in the
  ** process of being coded). If this is the case, then an entry with
  ** a matching TriggerPrg.pTrigger field will be present somewhere
  ** in the Parse.pTriggerPrg list. Search for such an entry.  */
  for(pPrg=pRoot->pTriggerPrg; 
      pPrg && (pPrg->pTrigger!=pTrigger || pPrg->orconf!=orconf); 

    ** legacy applications. */
    iDb = sqlite3FindDb(pParse->db, pNm);
    if( iDb<0 ) iDb = 0;
#endif
  }
  if( iDb!=1 ){
    int iIntoReg = 0;
    sqlite3SchemaWritable(pParse, iDb);
    if( pInto && sqlite3ResolveSelfReference(pParse,0,0,pInto,0)==0 ){
      iIntoReg = ++pParse->nMem;
      sqlite3ExprCode(pParse, pInto, iIntoReg);
    }
    sqlite3VdbeAddOp2(v, OP_Vacuum, iDb, iIntoReg);
    sqlite3VdbeUsesBtree(v, iDb);
  }

    }
  }
  assert( pOp->p5==0 || pOp->p4type==P4_INT32 );
  if( rc==SQLITE_OK
   && pOp->p5
   && (iMeta!=pOp->p3 || pDb->pSchema->iGeneration!=pOp->p4.i)
  ){
    /*
    ** IMPLEMENTATION-OF: R-03189-51135 As each SQL statement runs, the schema
    ** version is checked to ensure that the schema has not changed since the
    ** SQL statement was prepared.
    */
    sqlite3DbFree(db, p->zErrMsg);
    p->zErrMsg = sqlite3DbStrDup(db, "database schema has changed");
    /* If the schema-cookie from the database file matches the cookie
    ** stored with the in-memory representation of the schema, do
    ** not reload the schema from the database file.
    **
    ** If virtual-tables are in use, this is not just an optimization.
    ** Often, v-tables store their data in other SQLite tables, which
    ** are queried from within xNext() and other v-table methods using
    ** prepared queries. If such a query is out-of-date, we do not want to
    ** discard the database schema, as the user code implementing the
    ** v-table would have to be ready for the sqlite3_vtab structure itself
    ** to be invalidated whenever sqlite3_step() is called from within
    ** a v-table method.
    */
    if( db->aDb[pOp->p1].pSchema->schema_cookie!=iMeta ){
      sqlite3ResetOneSchema(db, pOp->p1);
    }
    /*
    ** IMPLEMENTATION-OF: R-03189-51135 As each SQL statement runs, the schema
    ** version is checked to ensure that the schema has not changed since the
    ** SQL statement was prepared.
    */
    sqlite3DbFree(db, p->zErrMsg);
    p->zErrMsg = sqlite3DbStrDup(db, "database schema has changed");
    p->expired = 1;
    rc = SQLITE_SCHEMA;

    /* Set changeCntOn to 0 to prevent the value returned by sqlite3_changes()
    ** from being modified in sqlite3VdbeHalt(). If this statement is
    ** reprepared, changeCntOn will be set again. */
    p->changeCntOn = 0;

# define sqlite3ExplainBreakpoint(A,B) /*no-op*/
#endif
#if defined(SQLITE_DEBUG) && !defined(SQLITE_OMIT_EXPLAIN)
  void sqlite3ExplainBreakpoint(const char*,const char*);
#else
# define sqlite3ExplainBreakpoint(A,B) /*no-op*/
#endif
void sqlite3VdbeAddParseSchemaOp(Vdbe*, int, char*, u16);
void sqlite3VdbeAddParseSchemaOp(Parse*,int,char*,u16);
void sqlite3VdbeChangeOpcode(Vdbe*, int addr, u8);
void sqlite3VdbeChangeP1(Vdbe*, int addr, int P1);
void sqlite3VdbeChangeP2(Vdbe*, int addr, int P2);
void sqlite3VdbeChangeP3(Vdbe*, int addr, int P3);
void sqlite3VdbeChangeP5(Vdbe*, u16 P5);
void sqlite3VdbeTypeofColumn(Vdbe*, int);
void sqlite3VdbeJumpHere(Vdbe*, int addr);

** Add an OP_ParseSchema opcode.  This routine is broken out from
** sqlite3VdbeAddOp4() since it needs to also needs to mark all btrees
** as having been used.
**
** The zWhere string must have been obtained from sqlite3_malloc().
** This routine will take ownership of the allocated memory.
*/
void sqlite3VdbeAddParseSchemaOp(Vdbe *p, int iDb, char *zWhere, u16 p5){
void sqlite3VdbeAddParseSchemaOp(Parse *pParse, int iDb, char *zWhere, u16 p5){
  Vdbe *p = pParse->pVdbe;
  int j;
  sqlite3SchemaWritable(pParse, iDb);
  sqlite3VdbeAddOp4(p, OP_ParseSchema, iDb, 0, 0, zWhere, P4_DYNAMIC);
  sqlite3VdbeChangeP5(p, p5);
  for(j=0; j<p->db->nDb; j++) sqlite3VdbeUsesBtree(p, j);
  sqlite3MayAbort(p->pParse);
}

/* Insert the end of a co-routine

  int iCol;               /* Index of zColumn in row-record */
  int rc = SQLITE_OK;
  char *zErr = 0;
  Table *pTab;
  Incrblob *pBlob = 0;
  int iDb;
  Parse sParse;
  int bUnlock;            /* True to unlock reusable schemas before returning */

#ifdef SQLITE_ENABLE_API_ARMOR
  if( ppBlob==0 ){
    return SQLITE_MISUSE_BKPT;
  }
#endif
  *ppBlob = 0;
#ifdef SQLITE_ENABLE_API_ARMOR
  if( !sqlite3SafetyCheckOk(db) || zTable==0 || zColumn==0 ){
    return SQLITE_MISUSE_BKPT;
  }
#endif
  wrFlag = !!wrFlag;                /* wrFlag = (wrFlag ? 1 : 0); */

  sqlite3_mutex_enter(db->mutex);

  bUnlock = sqlite3LockReusableSchema(db);
  pBlob = (Incrblob *)sqlite3DbMallocZero(db, sizeof(Incrblob));
  while(1){
    sqlite3ParseObjectInit(&sParse,db);
    if( !pBlob ) goto blob_open_out;
    sqlite3DbFree(db, zErr);
    zErr = 0;

    }
    rc = blobSeekToRow(pBlob, iRow, &zErr);
    if( (++nAttempt)>=SQLITE_MAX_SCHEMA_RETRY || rc!=SQLITE_SCHEMA ) break;
    sqlite3ParseObjectReset(&sParse);
  }

blob_open_out:
  sqlite3UnlockReusableSchema(db, bUnlock);
  if( rc==SQLITE_OK && db->mallocFailed==0 ){
    *ppBlob = (sqlite3_blob *)pBlob;
  }else{
    if( pBlob && pBlob->pStmt ) sqlite3VdbeFinalize((Vdbe *)pBlob->pStmt);
    sqlite3DbFree(db, pBlob);
  }
  sqlite3ErrorWithMsg(db, rc, (zErr ? "%s" : (char*)0), zErr);

** pTab is a pointer to a Table structure representing a virtual-table.
** Return a pointer to the VTable object used by connection db to access
** this virtual-table, if one has been created, or NULL otherwise.
*/
VTable *sqlite3GetVTable(sqlite3 *db, Table *pTab){
  VTable *pVtab;
  assert( IsVirtual(pTab) );
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  if( IsSharedSchema(db) ){
    int iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
    if( iDb!=1 ){
      VTable **pp;
      for(pp=&db->aDb[iDb].pVTable; *pp; pp=&(*pp)->pNext){
        if( sqlite3StrICmp(pTab->zName, (*pp)->zName)==0 ) break;
      }
      pVtab = *pp;
      if( pVtab && pTab->nCol<=0 ){
        *pp = pVtab->pNext;
        sqlite3VtabUnlock(pVtab);
        pVtab = 0;
      }
      return pVtab;
    }
  }
#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
  for(pVtab=pTab->u.vtab.p; pVtab && pVtab->db!=db; pVtab=pVtab->pNext);
  return pVtab;
}

/*
** Decrement the ref-count on a virtual table object. When the ref-count
** reaches zero, call the xDisconnect() method to delete the object.

      pParse->u1.cr.regRowid
    );
    v = sqlite3GetVdbe(pParse);
    sqlite3ChangeCookie(pParse, iDb);

    sqlite3VdbeAddOp0(v, OP_Expire);
    zWhere = sqlite3MPrintf(db, "name=%Q AND sql=%Q", pTab->zName, zStmt);
    sqlite3VdbeAddParseSchemaOp(v, iDb, zWhere, 0);
    sqlite3VdbeAddParseSchemaOp(pParse, iDb, zWhere, 0);
    sqlite3DbFree(db, zStmt);

    iReg = ++pParse->nMem;
    sqlite3VdbeLoadString(v, iReg, pTab->zName);
    sqlite3VdbeAddOp2(v, OP_VCreate, iDb, iReg);
  }else{
    /* If we are rereading the sqlite_schema table create the in-memory

  int rc;
  const char *const*azArg;
  int nArg = pTab->u.vtab.nArg;
  char *zErr = 0;
  char *zModuleName;
  int iDb;
  VtabCtx *pCtx;
  int nByte;                      /* Bytes of space to allocate */

  assert( IsVirtual(pTab) );
  azArg = (const char *const*)pTab->u.vtab.azArg;

  /* Check that the virtual-table is not already being initialized */
  for(pCtx=db->pVtabCtx; pCtx; pCtx=pCtx->pPrior){
    if( pCtx->pTab==pTab ){
      *pzErr = sqlite3MPrintf(db,
          "vtable constructor called recursively: %s", pTab->zName
      );
      return SQLITE_LOCKED;
    }
  }

  zModuleName = sqlite3DbStrDup(db, pTab->zName);
  if( !zModuleName ){
    return SQLITE_NOMEM_BKPT;
  }

  pVTable = sqlite3MallocZero(sizeof(VTable));
  nByte = sizeof(VTable);
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  nByte += sqlite3Strlen30(pTab->zName) + 1;
#endif
  pVTable = (VTable*)sqlite3MallocZero(nByte);
  if( !pVTable ){
    sqlite3OomFault(db);
    sqlite3DbFree(db, zModuleName);
    return SQLITE_NOMEM_BKPT;
  }
  pVTable->db = db;
  pVTable->pMod = pMod;
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
  pVTable->zName = (char*)&pVTable[1];
  memcpy(pVTable->zName, pTab->zName, nByte-sizeof(VTable));
#endif
  pVTable->eVtabRisk = SQLITE_VTABRISK_Normal;

  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
  pTab->u.vtab.azArg[1] = db->aDb[iDb].zDbSName;

  /* Invoke the virtual table constructor */
  assert( &db->pVtabCtx );

      *pzErr = sqlite3MPrintf(db, zFormat, zModuleName);
      sqlite3VtabUnlock(pVTable);
      rc = SQLITE_ERROR;
    }else{
      int iCol;
      u16 oooHidden = 0;
      /* If everything went according to plan, link the new VTable structure
      ** into the linked list headed by pTab->u.vtab.p. Then loop through the
      ** columns of the table to see if any of them contain the token "hidden".
      ** If so, set the Column COLFLAG_HIDDEN flag and remove the token from
      ** the type string.  */
      pVTable->pNext = pTab->u.vtab.p;
      pTab->u.vtab.p = pVTable;
      ** into the linked list headed by pTab->u.vtab.p. Or, if this is a
      ** reusable schema, into the linked list headed by Db.pVTable.
      **
      ** Then loop through the columns of the table to see if any of them
      ** contain the token "hidden". If so, set the Column COLFLAG_HIDDEN flag
      ** and remove the token from the type string.  */
#ifdef SQLITE_ENABLE_SHARED_SCHEMA
      if( IsSharedSchema(db) && iDb!=1 ){
        pVTable->pNext = db->aDb[iDb].pVTable;
        db->aDb[iDb].pVTable = pVTable;
      }else
#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
      {
        assert( IsVirtual(pTab) );
        pVTable->pNext = pTab->u.vtab.p;
        pTab->u.vtab.p = pVTable;
      }

      for(iCol=0; iCol<pTab->nCol; iCol++){
        char *zType = sqlite3ColumnType(&pTab->aCol[iCol], "");
        int nType;
        int i = 0;
        nType = sqlite3Strlen30(zType);
        for(i=0; i<nType; i++){

  const char *zMod;
  Module *pMod;
  int rc;

  assert( pTab );
  assert( IsVirtual(pTab) );
  if( sqlite3GetVTable(db, pTab) ){
    assert( !IsVirtual(pTab) || pTab->nCol>0 );
    return SQLITE_OK;
  }

  /* Locate the required virtual table module */
  zMod = pTab->u.vtab.azArg[0];
  pMod = (Module*)sqlite3HashFind(&db->aModule, zMod);

      sqlite3OomFault(pParse->db);
    }else if( !pVtab->zErrMsg ){
      sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
    }else{
      sqlite3ErrorMsg(pParse, "%s", pVtab->zErrMsg);
    }
  }
  if( pTab->u.vtab.p->bAllSchemas ){
  if( pTab->u.vtab.p && pTab->u.vtab.p->bAllSchemas ){
    sqlite3VtabUsesAllSchemas(pParse);
  }
  sqlite3_free(pVtab->zErrMsg);
  pVtab->zErrMsg = 0;
  return rc;
}
#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) */

# This file implements regression tests for SQLite library.  The
# focus of this file is testing the nolock=1 and immutable=1 query
# parameters and the SQLITE_IOCAP_IMMUTABLE device characteristic.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix nolock

unset -nocomplain tvfs_calls
proc tvfs_reset {} {
  global tvfs_calls
  array set tvfs_calls {xLock 0 xUnlock 0 xCheckReservedLock 0 xAccess 0}
}
proc tvfs_callback {op args} {

    db close
    sqlite3 db file:test.db?nolock=1 -uri 1
    set rc [catch {db eval {SELECT * FROM t1}} msg]
    lappend rc $msg
  } {1 {unable to open database file}}
}

#-------------------------------------------------------------------------
reset_db
do_execsql_test 5.0 {
  CREATE TABLE t1(x, y);
  CREATE TABLE t2(x, y);
  INSERT INTO t1 VALUES(1, 2), (3, 4), (5, 6);
  INSERT INTO t2 VALUES(1, 2), (3, 4), (5, 6);
  PRAGMA cache_size = 0;
  BEGIN;
    INSERT INTO t1 VALUES(7, 8);
    INSERT INTO t2 VALUES(7, 8);
}

do_test 5.1 {
  forcecopy test.db test.db2
  forcecopy test.db-journal test.db2-journal
  sqlite3 db2 file:test.db2?immutable=0 -uri 1 -readonly 1

  list [catch {
    db2 eval {
      SELECT * FROM t1;
      SELECT * FROM t2;
    }
  } msg] $msg
} {1 {attempt to write a readonly database}}

finish_test

# 2024 October 30
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# Test that readonly database connections may ignore a hot journal 
# created by an aborted "PRAGMA journal_mode = wal" statement.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
ifcapable !readonly_waljournal {
  finish_test
  return
}

set ::testprefix readonly2

testvfs tvfs -default 1
tvfs script at_vfs_callback
tvfs filter {xDelete}

set ::delete_shall_fail 0
proc at_vfs_callback {method file z args} {
  if {$::delete_shall_fail} {
    return "SQLITE_IOERR"
  }
  return "SQLITE_OK"
}

reset_db
do_execsql_test 1.0 {
  BEGIN;
    CREATE TABLE t1(a, b);
    INSERT INTO t1 VALUES(1, 2), (3, 4), (5, 6);
  COMMIT;
}

set ::delete_shall_fail 1
do_catchsql_test 1.1 {
  PRAGMA journal_mode = wal;
} {1 {disk I/O error}}

do_test 1.2 {
  file exists test.db-journal
} 1

do_test 1.3 {
  sqlite3 db2 test.db -readonly 1
  db2 eval {
    SELECT * FROM t1
  }
} {1 2 3 4 5 6}

do_test 1.4 {
  file exists test.db-journal
} 1

set ::delete_shall_fail 0
do_execsql_test 1.5 {
  SELECT * FROM t1
} {1 2 3 4 5 6}

set ::delete_shall_fail 1
do_catchsql_test 1.6 {
  PRAGMA user_version = 444;
} {1 {disk I/O error}}
 
do_test 1.7 {
  file exists test.db-journal
} 1

do_test 1.8 {
  list [catch { db2 eval { SELECT * FROM t1 } } msg] $msg
} {1 {attempt to write a readonly database}}

do_test 1.9 {
  file exists test.db-journal
} 1

set ::delete_shall_fail 0
do_execsql_test 1.10 {
  SELECT * FROM t1
} {1 2 3 4 5 6}

#---------------------------------------------------------
reset_db

do_execsql_test 2.1 {
  CREATE TABLE t1(a, b);
  INSERT INTO t1 VALUES('abc', 'def');
}

set ::delete_shall_fail 1
do_catchsql_test 2.2 {
  PRAGMA journal_mode = wal;
} {1 {disk I/O error}}

do_test 2.3 {
  sqlite3 db2 test.db -readonly 1
  breakpoint
  db2 eval {
    PRAGMA journal_mode = persist;
    PRAGMA journal_mode = off;
  }
} {persist off}

do_test 2.4 {
  db2 eval {
    SELECT * FROM t1
  }
} {abc def}

finish_test