SQLite

    Table *pStat;
    if( (pStat = sqlite3FindTable(db, zTab, pDb->zDbSName))==0 ){
      if( aTable[i].zCols ){
        /* 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
        );
        aRoot[i] = pParse->regRoot;
        aCreateTbl[i] = OPFLAG_P2ISREG;
      }
    }else{

  sqlite3 *db = pParse->db;
  Schema *pSchema = db->aDb[iDb].pSchema;    /* Schema of database iDb */
  HashElem *k;
  int iStatCur;
  int iMem;
  int iTab;


  sqlite3BeginWriteOperation(pParse, 0, iDb);
  iStatCur = pParse->nTab;
  pParse->nTab += 3;
  openStatTable(pParse, iDb, iStatCur, 0, 0);
  iMem = pParse->nMem+1;
  iTab = pParse->nTab;
  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );

  Schema *pSchema;                /* Linked list of Schema objects */
  Schema sSchema;                 /* The single dummy schema object */
  SchemaPool *pNext;              /* Next element in schemaPoolList */
};

#ifdef SQLITE_DEBUG
static void assert_schema_state_ok(sqlite3 *db){
  if( IsReuseSchema(db) && db->magic!=SQLITE_MAGIC_ZOMBIE ){
    int i;
    for(i=0; i<db->nDb; i++){
      if( i!=1 ){
        Db *pDb = &db->aDb[i];
        Btree *pBt = pDb->pBt;
        if( pDb->pSPool ){
          if( DbHasProperty(db, i, DB_SchemaLoaded)==0 ){

      sqlite3OomFault(db);
    }
    sqlite3ResetOneSchema(db, iDb);
  }
  db->init.busy = 0;
  return rc;
}

int sqlite3LockReusableSchema(sqlite3 *db){
  if( IsReuseSchema(db) && (db->mDbFlags & DBFLAG_SchemaInuse)==0 ){
    db->mDbFlags |= DBFLAG_SchemaInuse;
    return 1;
  }
  return 0;
}
void sqlite3UnlockReusableSchema(sqlite3 *db, int bRelease){
  if( bRelease ){
    db->mDbFlags &= ~DBFLAG_SchemaInuse;
    sqlite3SchemaReleaseAll(db);
  }
}

/*
** 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. If the database
** file was of zero-length, then the DB_Empty flag is also set.
*/
int sqlite3Init(sqlite3 *db, char **pzErrMsg){
  int rc = SQLITE_OK;
  int bReleaseSchema;
  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);

  }
  /* All other schemas after the main schema. The "temp" schema must be last */
  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==SQLITE_OK && commit_internal ){
    sqlite3CommitInternalChanges(db);
  }
  sqlite3UnlockReusableSchema(db, bReleaseSchema);
  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){

  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 );
  }while( rc==SQLITE_ERROR_RETRY
       || (rc==SQLITE_SCHEMA && (sqlite3ResetOneSchema(db,-1), cnt++)==0) );

  sqlite3BtreeLeaveAll(db);

  sqlite3UnlockReusableSchema(db, bReleaseSchema);




  rc = sqlite3ApiExit(db, rc);
  assert( (rc&db->errMask)==rc );
  sqlite3_mutex_leave(db->mutex);
  return rc;
}

  u8 op;                  /* One of TK_DELETE, TK_UPDATE, TK_INSERT         */
  u8 tr_tm;               /* One of TRIGGER_BEFORE, TRIGGER_AFTER */
  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 */
  char *zTabSchema;       /* Temp triggers in IsReuseSchema() dbs only */
  TriggerStep *step_list; /* Link list of trigger program steps             */
  Trigger *pNext;         /* Next trigger associated with the table */
};

/*
** A trigger is either a BEFORE or an AFTER trigger.  The following constants
** determine which.

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);

void sqlite3UnlockReusableSchema(sqlite3 *db, int bRelease);
int sqlite3LockReusableSchema(sqlite3 *db);

#ifdef SQLITE_DEBUG
int sqlite3KeyInfoIsWriteable(KeyInfo*);
#endif
int sqlite3CreateFunc(sqlite3 *, const char *, int, int, void *,
  void (*)(sqlite3_context*,int,sqlite3_value **),
  void (*)(sqlite3_context*,int,sqlite3_value **), 

  Trigger *pList = 0;                  /* List of triggers to return */

  if( pParse->disableTriggers ){
    return 0;
  }

  if( pTmpSchema!=pTab->pSchema ){
    sqlite3 *db = pParse->db;
    HashElem *p;
    char *zSchema = 0;
    if( IsReuseSchema(db) ){
      zSchema = db->aDb[sqlite3SchemaToIndex(db, pTab->pSchema)].zDbSName;
    }
    assert( sqlite3SchemaMutexHeld(db, 0, pTmpSchema) );
    for(p=sqliteHashFirst(&pTmpSchema->trigHash); p; p=sqliteHashNext(p)){
      Trigger *pTrig = (Trigger *)sqliteHashData(p);
      if( (zSchema==0 && pTrig->pTabSchema==pTab->pSchema)
       || (zSchema!=0 && 0==sqlite3StrICmp(pTrig->zTabSchema, zSchema))
      ){
        if( 0==sqlite3StrICmp(pTrig->table, pTab->zName) 
      ){
          pTrig->pTabSchema = pTab->pSchema;
        pTrig->pNext = (pList ? pList : pTab->pTrigger);
        pList = pTrig;
      }
    }
  }
  }

  return (pList ? pList : pTab->pTrigger);
}

/*
** This is called by the parser when it sees a CREATE TRIGGER statement
** up to the point of the BEGIN before the trigger actions.  A Trigger

  /* 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);
  if( IsReuseSchema(db) && iDb==1 ){
    int iTabDb = sqlite3SchemaToIndex(db, pTab->pSchema);
    pTrigger->zTabSchema = sqlite3DbStrDup(db, db->aDb[iTabDb].zDbSName);
  }
  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;

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

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

** then runs the new virtual machine.  It is thus a re-entrant opcode.
*/
case OP_ParseSchema: {
  int iDb;
  const char *zMaster;
  char *zSql;
  InitData initData;
  int bRelease;

  /* Any prepared statement that invokes this opcode will hold mutexes
  ** on every btree.  This is a prerequisite for invoking 
  ** sqlite3InitCallback().
  */
#ifdef SQLITE_DEBUG
  for(iDb=0; iDb<db->nDb; iDb++){

    initData.mInitFlags = 0;
    zSql = sqlite3MPrintf(db,
       "SELECT name, rootpage, sql FROM '%q'.%s WHERE %s ORDER BY rowid",
       db->aDb[iDb].zDbSName, zMaster, pOp->p4.z);
    if( zSql==0 ){
      rc = SQLITE_NOMEM_BKPT;
    }else{
      bRelease = sqlite3LockReusableSchema(db);
      if( IsReuseSchema(db) ){
        rc = sqlite3Init(db, &p->zErrMsg);
        if( rc ){
          sqlite3UnlockReusableSchema(db, bRelease);
          goto abort_due_to_error;
        }
      }
      assert( db->init.busy==0 );
      db->init.busy = 1;
      initData.rc = SQLITE_OK;
      initData.nInitRow = 0;
      assert( !db->mallocFailed );
      rc = sqlite3_exec(db, zSql, sqlite3InitCallback, &initData, 0);
      sqlite3UnlockReusableSchema(db, bRelease);
      if( rc==SQLITE_OK ) rc = initData.rc;
      if( rc==SQLITE_OK && initData.nInitRow==0 ){
        /* The OP_ParseSchema opcode with a non-NULL P4 argument should parse
        ** at least one SQL statement. Any less than that indicates that
        ** the sqlite_master table is corrupt. */
        rc = SQLITE_CORRUPT_BKPT;
      }

#


set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix reuse1

if 1 {

forcedelete test.db2
sqlite3 db2 test.db2

do_execsql_test 1.0 {
  CREATE TABLE t1(x INTEGER PRIMARY KEY, y UNIQUE, z);
  CREATE INDEX i1 ON t1(z);

  7  { DROP INDEX i1 }
  8  { DROP TABLE t1 }
  9  { DROP TRIGGER tr1 }
  10 { ANALYZE }
} {
  do_catchsql_test 1.5.$tn $sql {1 {attempt to modify read-only schema}}
}

#-------------------------------------------------------------------------
#
reset_db
forcedelete test.db2
ifcapable fts5 {
  do_execsql_test 2.0 {
    CREATE VIRTUAL TABLE ft USING fts5(a);
    INSERT INTO ft VALUES('one'), ('two'), ('three');
    ATTACH 'test.db2' AS aux;
    CREATE VIRTUAL TABLE aux.ft USING fts5(a);
    INSERT INTO aux.ft VALUES('aux1'), ('aux2'), ('aux3');
  }

  db close
  sqlite3 db  test.db -reuse-schema 1

  do_execsql_test 2.1 {
    ATTACH 'test.db2' AS aux;
    SELECT * FROM main.ft;
  } {one two three}

  do_execsql_test 2.2 {
    SELECT * FROM aux.ft;
  } {aux1 aux2 aux3}

  do_execsql_test 2.2 {
    SELECT * FROM aux.ft_content;
  } {1 aux1 2 aux2 3 aux3}
}

}

#-------------------------------------------------------------------------
#
reset_db
forcedelete test.db2
do_execsql_test 3.0 {
  CREATE TABLE t1(a PRIMARY KEY, b, c);
  CREATE VIEW v1 AS SELECT * FROM t1;
  CREATE TRIGGER v1_ins INSTEAD OF INSERT ON v1 BEGIN
    INSERT INTO t1 VALUES(new.a, new.b, new.c);
  END;
  CREATE TRIGGER v1_del INSTEAD OF DELETE ON v1 BEGIN
    DELETE FROM t1 WHERE a=old.a;
  END;
  CREATE TRIGGER v1_up INSTEAD OF UPDATE ON v1 BEGIN
    UPDATE t1 SET a=new.a, b=new.b, c=new.c WHERE a=old.a;
  END;
}
forcecopy test.db test.db2

do_test 3.1 {
  sqlite3 db2 test.db2
  execsql { INSERT INTO t1 VALUES(1, 2, 3) } db
  execsql { INSERT INTO t1 VALUES(4, 5, 6) } db2
  db2 close
  execsql { ATTACH 'test.db2' AS aux; }
} {}

do_execsql_test 3.2 {
  SELECT * FROM main.v1;
} {1 2 3}

do_execsql_test 3.3 {
  SELECT * FROM aux.v1;
} {4 5 6}

db close
sqlite3 db test.db -reuse-schema 1

do_execsql_test 3.4 { ATTACH 'test.db2' AS aux } {}
do_execsql_test 3.5 { SELECT * FROM main.v1 } {1 2 3}
do_execsql_test 3.6 { SELECT * FROM aux.v1  } {4 5 6}

do_execsql_test 3.7.1 { INSERT INTO aux.t1 VALUES(8, 9, 10); }
do_execsql_test 3.7.2 { SELECT * FROM main.v1 } {1 2 3}
do_execsql_test 3.7.3 { SELECT * FROM aux.v1  } {4 5 6 8 9 10}

do_execsql_test 3.8.1 { DELETE FROM aux.t1 WHERE b=5 }
do_execsql_test 3.8.2 { SELECT * FROM main.v1 } {1 2 3}
do_execsql_test 3.8.3 { SELECT * FROM aux.v1  } {8 9 10}

do_execsql_test 3.9.1 { UPDATE aux.t1 SET b='abc' }
do_execsql_test 3.9.2 { SELECT * FROM main.v1 } {1 2 3}
do_execsql_test 3.9.3 { SELECT * FROM aux.v1  } {8 abc 10}

do_execsql_test 3.10.1 { INSERT INTO aux.v1 VALUES(11, 12, 13) }
do_execsql_test 3.10.2 { SELECT * FROM main.v1 } {1 2 3}
do_execsql_test 3.10.3 { SELECT * FROM aux.v1  } {8 abc 10 11 12 13}

do_execsql_test 3.11.1 { DELETE FROM aux.v1 WHERE b='abc' }
do_execsql_test 3.11.2 { SELECT * FROM main.v1 } {1 2 3}
do_execsql_test 3.11.3 { SELECT * FROM aux.v1  } {11 12 13}

do_execsql_test 3.12.1 { UPDATE aux.v1 SET b='def' }
do_execsql_test 3.12.2 { SELECT * FROM main.v1 } {1 2 3}
do_execsql_test 3.12.3 { SELECT * FROM aux.v1  } {11 def 13}

do_execsql_test 3.13.1 {
  CREATE TEMP TRIGGER xyz AFTER INSERT ON aux.t1 BEGIN
    INSERT INTO v1 VALUES(new.a, new.b, new.c);
  END
}
do_execsql_test 3.13.2 {
  INSERT INTO aux.v1 VALUES('x', 'y', 'z');
}
do_execsql_test 3.13.3 {
  SELECT * FROM v1;
} {1 2 3 x y z}

#-------------------------------------------------------------------------
#
reset_db
forcedelete test.db2
do_execsql_test 4.0 {
  CREATE TABLE t1(a PRIMARY KEY, b, c UNIQUE);
  CREATE TABLE del(a, b, c);
  CREATE TRIGGER tr1 AFTER DELETE ON t1 BEGIN
    INSERT INTO del VALUES(old.a, old.b, old.c);
  END;
}
forcecopy test.db test.db2

db close
sqlite3 db test.db -reuse-schema 1
execsql { 
  ATTACH 'test.db2' AS aux;
  PRAGMA recursive_triggers = 1;
}

do_execsql_test 4.1 {
  INSERT INTO main.t1 VALUES(1, 2, 3);
  INSERT INTO aux.t1 VALUES(4, 5, 6);
}

do_execsql_test 4.2.1 {
  INSERT OR REPLACE INTO aux.t1 VALUES('a', 'b', 6);
  SELECT * FROM aux.t1;
} {a b 6}
do_execsql_test 4.2.2 { SELECT * FROM aux.del  } {4 5 6}
do_execsql_test 4.2.3 { SELECT * FROM main.del } {}

do_execsql_test 4.3.1 {
  INSERT INTO aux.t1 VALUES('x', 'y', 'z');
  UPDATE OR REPLACE aux.t1 SET c='z' WHERE a='a';
} {}
do_execsql_test 4.3.2 { SELECT * FROM aux.del  } {4 5 6 x y z}
do_execsql_test 4.3.3 { SELECT * FROM main.del } {}

#-------------------------------------------------------------------------
#
reset_db
do_execsql_test 5.0 {
  CREATE TABLE t1(a INTEGER PRIMARY KEY, b, c);
  CREATE TABLE t2(a INTEGER PRIMARY KEY, b, c);
  CREATE INDEX i1 ON t1(b);
  INSERT INTO t1 VALUES(1, 2, 3), (4, 5, 6);
  ANALYZE;
  PRAGMA writable_schema = 1;
  DELETE FROM sqlite_stat1;
}
db close
forcecopy test.db test.db2
sqlite3 db test.db -reuse-schema 1
execsql { ATTACH 'test.db2' AS aux }

foreach {tn sql} {
  1 { CREATE TABLE t3(x) }
  2 { DROP TABLE t2 }
  3 { CREATE INDEX i2 ON t2(b) }
  4 { DROP INDEX i1 }
  5 { ALTER TABLE t1 ADD COLUMN d }
  6 { ALTER TABLE t1 RENAME TO t3 }
  7 { ALTER TABLE t1 RENAME c TO d }
} {
  do_catchsql_test 5.1.$tn $sql {1 {attempt to modify read-only schema}}
}

do_execsql_test 5.2.1 { ANALYZE aux.t1 } {}
do_execsql_test 5.2.2 { SELECT * FROM aux.sqlite_stat1  } {t1 i1 {2 1}}
do_execsql_test 5.2.3 { SELECT * FROM main.sqlite_stat1 } {}

do_test 5.3.0 {
  sqlite3 db2 test.db2
  db2 eval { 
    PRAGMA writable_schema = 1;
    DELETE FROM sqlite_stat1;
  }
} {}

do_execsql_test 5.3.1 { SELECT * FROM aux.sqlite_stat1  } {}
do_execsql_test 5.3.2 { ANALYZE aux } {}
do_execsql_test 5.3.3 { SELECT * FROM aux.sqlite_stat1  } {t1 i1 {2 1}}
do_execsql_test 5.3.4 { SELECT * FROM main.sqlite_stat1 } {}

#-------------------------------------------------------------------------
# Attempting to run ANALYZE when the required sqlite_statXX functions
# are missing is an error (because it would modify the database schema).
#
reset_db
do_execsql_test 5.4 {
  CREATE TABLE t1(a INTEGER PRIMARY KEY, b, c);
  CREATE TABLE t2(a INTEGER PRIMARY KEY, b, c);
  CREATE INDEX i1 ON t1(b);
  INSERT INTO t1 VALUES(1, 2, 3), (4, 5, 6);
}
db close
sqlite3 db test.db -reuse-schema 1
breakpoint
foreach {tn sql} {
  1 { ANALYZE }
  2 { ANALYZE t1 }
  3 { ANALYZE i1 }
  4 { ANALYZE main }
  5 { ANALYZE main.t1 }
  6 { ANALYZE main.i1 }
} {
  do_catchsql_test 5.4.$tn $sql {1 {attempt to modify read-only schema}}
}

#-------------------------------------------------------------------------
#
reset_db
do_execsql_test 6.0 {
  CREATE TABLE t1(a INTEGER PRIMARY KEY, b, c);
  CREATE VIEW v1 AS SELECT * FROM t1;
}
db close
forcecopy test.db test.db2
sqlite3 db test.db -reuse-schema 1
execsql { ATTACH 'test.db2' AS aux }

do_execsql_test 6.1 {
  INSERT INTO main.t1(a) VALUES(1), (2), (3);
  INSERT INTO aux.t1(a) VALUES(4), (5), (6);
  CREATE TEMP TABLE t2(i,t);
  INSERT INTO t2 VALUES(2, 'two'), (5, 'five');
}

do_execsql_test 6.2 {
  SELECT t FROM t2 WHERE i IN (SELECT a FROM aux.t1)
} {five}
do_execsql_test 6.3 {
  SELECT t FROM t2 WHERE i IN (SELECT a FROM aux.v1)
} {five}

#-------------------------------------------------------------------------
#
reset_db
do_execsql_test 7.0 {
  CREATE TABLE p1(a PRIMARY KEY, b);
  CREATE TABLE p2(a PRIMARY KEY, b);
  CREATE TABLE c1(x REFERENCES p1 ON UPDATE CASCADE ON DELETE CASCADE);
}

db close
forcecopy test.db test.db2
sqlite3 db test.db -reuse-schema 1
execsql { ATTACH 'test.db2' AS aux }

do_execsql_test 7.1 {
  INSERT INTO aux.p1 VALUES(1, 'one');
  INSERT INTO aux.p1 VALUES(2, 'two');
  PRAGMA foreign_keys = on;
}

do_execsql_test 7.2 {
  INSERT INTO aux.c1 VALUES(2);
}

do_execsql_test 7.3.1 {
  PRAGMA foreign_keys = off;
  INSERT INTO main.p2 SELECT * FROM aux.p1;
}
do_execsql_test 7.3.2 {
  SELECT * FROM main.p2;
} {1 one 2 two}

do_execsql_test 7.3.3 {
  INSERT INTO aux.p2 VALUES(1, 2);
}

do_execsql_test 7.3.4 {
  SELECT main.p2.a FROM main.p2, aux.p2;
} {1 2}

do_execsql_test 7.3.5 {
  SELECT * FROM main.p2, aux.p2;
} {1 one 1 2   2 two 1 2}

do_execsql_test 7.4 {
  SELECT count(*) FROM aux.p2;
} {1}


finish_test