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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

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Overview
Comment:Add the ability to disable the push-down optimization using the 0x1000 bit of SQLITE_TESTCTRL_OPTIMIZATIONS. Also some documentation fixes and an enhancement to ".eqp full" in the CLI.
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SHA3-256: ae34edb7f4fa7b37a66cdf3a1d851980cb013e9abe72bdeca23e5323051e0646
User & Date: drh 2018-03-20 13:26:03
References
2018-06-07
15:11 New ticket [7be932df] Adverse interaction between .stats and .eqp in the CLI. artifact: facdb8d3 user: drh
Context
2018-03-20
13:44
Avoid unnecessary write to the sqlite_sequence table when an insert is done into an autoincrement table with an application-specified rowid that is less than the maximum. check-in: ec7addc8 user: drh tags: trunk
13:26
Add the ability to disable the push-down optimization using the 0x1000 bit of SQLITE_TESTCTRL_OPTIMIZATIONS. Also some documentation fixes and an enhancement to ".eqp full" in the CLI. check-in: ae34edb7 user: drh tags: trunk
13:00
Remove a debugging statement accidently left in check-in [eddc35f3057e59fd] Closed-Leaf check-in: 85a31557 user: drh tags: push-down-disable
2018-03-19
22:28
Minor improvements to ".selecttrace". No changes to non-debug code. check-in: 03e541f6 user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/select.c.

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    */
    pParse->nHeight += sqlite3SelectExprHeight(p);

    /* Make copies of constant WHERE-clause terms in the outer query down
    ** inside the subquery.  This can help the subquery to run more efficiently.
    */
    if( (pItem->fg.jointype & JT_OUTER)==0

     && pushDownWhereTerms(pParse, pSub, p->pWhere, pItem->iCursor)
    ){
#if SELECTTRACE_ENABLED
      if( sqlite3SelectTrace & 0x100 ){
        SELECTTRACE(0x100,pParse,p,("After WHERE-clause push-down:\n"));
        sqlite3TreeViewSelect(0, p, 0);
      }
#endif


    }

    zSavedAuthContext = pParse->zAuthContext;
    pParse->zAuthContext = pItem->zName;

    /* Generate code to implement the subquery
    **







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    */
    pParse->nHeight += sqlite3SelectExprHeight(p);

    /* Make copies of constant WHERE-clause terms in the outer query down
    ** inside the subquery.  This can help the subquery to run more efficiently.
    */
    if( (pItem->fg.jointype & JT_OUTER)==0
     && OptimizationEnabled(db, SQLITE_PushDown)
     && pushDownWhereTerms(pParse, pSub, p->pWhere, pItem->iCursor)
    ){
#if SELECTTRACE_ENABLED
      if( sqlite3SelectTrace & 0x100 ){
        SELECTTRACE(0x100,pParse,p,("After WHERE-clause push-down:\n"));
        sqlite3TreeViewSelect(0, p, 0);
      }
#endif
    }else{
      SELECTTRACE(0x100,pParse,p,("Push-down not possible\n"));
    }

    zSavedAuthContext = pParse->zAuthContext;
    pParse->zAuthContext = pItem->zName;

    /* Generate code to implement the subquery
    **

Changes to src/shell.c.in.

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            explain_data_prepare(pArg, pExplain);
            exec_prepared_stmt(pArg, pExplain);
            explain_data_delete(pArg);
          }
          sqlite3_finalize(pExplain);
          sqlite3_free(zEQP);
        }

        sqlite3_db_config(db, SQLITE_DBCONFIG_TRIGGER_EQP, triggerEQP, 0);




        restore_debug_trace_modes();
      }

      if( pArg ){
        pArg->cMode = pArg->mode;
        if( pArg->autoExplain
         && sqlite3_column_count(pStmt)==8







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            explain_data_prepare(pArg, pExplain);
            exec_prepared_stmt(pArg, pExplain);
            explain_data_delete(pArg);
          }
          sqlite3_finalize(pExplain);
          sqlite3_free(zEQP);
        }
        if( pArg->autoEQP>=AUTOEQP_trigger && triggerEQP==0 ){
          sqlite3_db_config(db, SQLITE_DBCONFIG_TRIGGER_EQP, 0, 0);
          /* Reprepare pStmt before reactiving trace modes */
          sqlite3_finalize(pStmt);
          sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
        }
        restore_debug_trace_modes();
      }

      if( pArg ){
        pArg->cMode = pArg->mode;
        if( pArg->autoExplain
         && sqlite3_column_count(pStmt)==8

Changes to src/sqlite.h.in.

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**
** <dt>SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE</dt>
** <dd> Usually, when a database in wal mode is closed or detached from a 
** database handle, SQLite checks if this will mean that there are now no 
** connections at all to the database. If so, it performs a checkpoint 
** operation before closing the connection. This option may be used to
** override this behaviour. The first parameter passed to this operation
** is an integer - non-zero to disable checkpoints-on-close, or zero (the

** default) to enable them. The second parameter is a pointer to an integer
** into which is written 0 or 1 to indicate whether checkpoints-on-close
** have been disabled - 0 if they are not disabled, 1 if they are.
** </dd>

** <dt>SQLITE_DBCONFIG_ENABLE_QPSG</dt>
** <dd>^(The SQLITE_DBCONFIG_ENABLE_QPSG option activates or deactivates
** the [query planner stability guarantee] (QPSG).  When the QPSG is active,
** a single SQL query statement will always use the same algorithm regardless
** of values of [bound parameters].)^ The QPSG disables some query optimizations
** that look at the values of bound parameters, which can make some queries
** slower.  But the QPSG has the advantage of more predictable behavior.  With
** the QPSG active, SQLite will always use the same query plan in the field as
** was used during testing in the lab.





** </dd>

** <dt>SQLITE_DBCONFIG_TRIGGER_EQP</dt>
** <dd> By default, the output of EXPLAIN QUERY PLAN commands does not 
** include output for any operations performed by trigger programs. This
** option is used to set or clear (the default) a flag that governs this
** behavior. The first parameter passed to this operation is an integer -
** non-zero to enable output for trigger programs, or zero to disable it.

** The second parameter is a pointer to an integer into which is written 
** 0 or 1 to indicate whether output-for-triggers has been disabled - 0 if 
** it is not disabled, 1 if it is.  
** </dd>
** </dl>
*/
#define SQLITE_DBCONFIG_MAINDBNAME            1000 /* const char* */







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**
** <dt>SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE</dt>
** <dd> Usually, when a database in wal mode is closed or detached from a 
** database handle, SQLite checks if this will mean that there are now no 
** connections at all to the database. If so, it performs a checkpoint 
** operation before closing the connection. This option may be used to
** override this behaviour. The first parameter passed to this operation
** is an integer - positive to disable checkpoints-on-close, or zero (the
** default) to enable them, and negative to leave the setting unchanged.
** The second parameter is a pointer to an integer
** into which is written 0 or 1 to indicate whether checkpoints-on-close
** have been disabled - 0 if they are not disabled, 1 if they are.
** </dd>
**
** <dt>SQLITE_DBCONFIG_ENABLE_QPSG</dt>
** <dd>^(The SQLITE_DBCONFIG_ENABLE_QPSG option activates or deactivates
** the [query planner stability guarantee] (QPSG).  When the QPSG is active,
** a single SQL query statement will always use the same algorithm regardless
** of values of [bound parameters].)^ The QPSG disables some query optimizations
** that look at the values of bound parameters, which can make some queries
** slower.  But the QPSG has the advantage of more predictable behavior.  With
** the QPSG active, SQLite will always use the same query plan in the field as
** was used during testing in the lab.
** The first argument to this setting is an integer which is 0 to disable 
** the QPSG, positive to enable QPSG, or negative to leave the setting
** unchanged. The second parameter is a pointer to an integer into which
** is written 0 or 1 to indicate whether the QPSG is disabled or enabled
** following this call.
** </dd>
**
** <dt>SQLITE_DBCONFIG_TRIGGER_EQP</dt>
** <dd> By default, the output of EXPLAIN QUERY PLAN commands does not 
** include output for any operations performed by trigger programs. This
** option is used to set or clear (the default) a flag that governs this
** behavior. The first parameter passed to this operation is an integer -
** positive to enable output for trigger programs, or zero to disable it,
** or negative to leave the setting unchanged.
** The second parameter is a pointer to an integer into which is written 
** 0 or 1 to indicate whether output-for-triggers has been disabled - 0 if 
** it is not disabled, 1 if it is.  
** </dd>
** </dl>
*/
#define SQLITE_DBCONFIG_MAINDBNAME            1000 /* const char* */

Changes to src/sqliteInt.h.

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#define SQLITE_OrderByIdxJoin 0x0040   /* ORDER BY of joins via index */
#define SQLITE_Transitive     0x0080   /* Transitive constraints */
#define SQLITE_OmitNoopJoin   0x0100   /* Omit unused tables in joins */
#define SQLITE_CountOfView    0x0200   /* The count-of-view optimization */
#define SQLITE_CursorHints    0x0400   /* Add OP_CursorHint opcodes */
#define SQLITE_Stat34         0x0800   /* Use STAT3 or STAT4 data */
   /* TH3 expects the Stat34  ^^^^^^ value to be 0x0800.  Don't change it */

#define SQLITE_AllOpts        0xffff   /* All optimizations */

/*
** Macros for testing whether or not optimizations are enabled or disabled.
*/
#define OptimizationDisabled(db, mask)  (((db)->dbOptFlags&(mask))!=0)
#define OptimizationEnabled(db, mask)   (((db)->dbOptFlags&(mask))==0)







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#define SQLITE_OrderByIdxJoin 0x0040   /* ORDER BY of joins via index */
#define SQLITE_Transitive     0x0080   /* Transitive constraints */
#define SQLITE_OmitNoopJoin   0x0100   /* Omit unused tables in joins */
#define SQLITE_CountOfView    0x0200   /* The count-of-view optimization */
#define SQLITE_CursorHints    0x0400   /* Add OP_CursorHint opcodes */
#define SQLITE_Stat34         0x0800   /* Use STAT3 or STAT4 data */
   /* TH3 expects the Stat34  ^^^^^^ value to be 0x0800.  Don't change it */
#define SQLITE_PushDown       0x1000   /* The push-down optimization */
#define SQLITE_AllOpts        0xffff   /* All optimizations */

/*
** Macros for testing whether or not optimizations are enabled or disabled.
*/
#define OptimizationDisabled(db, mask)  (((db)->dbOptFlags&(mask))!=0)
#define OptimizationEnabled(db, mask)   (((db)->dbOptFlags&(mask))==0)