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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Change the 0x800 bit of SQLITE_TESTCTRL_OPTIMIZATIONS so that it disables the loading of STAT3 and STAT4 content, not just the using of that content. Change the internal name of that bit to SQLITE_Stat34.
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SHA1: ca3b00c44ec52d209642a5ba9ef82e085fac39db
User & Date: drh 2014-10-22 19:57:16
Context
2014-10-22
20:07
Disable the use of strchrnul() unless specifically enabled by compile-time options. check-in: e580470d user: drh tags: trunk
19:57
Change the 0x800 bit of SQLITE_TESTCTRL_OPTIMIZATIONS so that it disables the loading of STAT3 and STAT4 content, not just the using of that content. Change the internal name of that bit to SQLITE_Stat34. check-in: ca3b00c4 user: drh tags: trunk
15:27
Take steps to avoid misestimating range query costs based on STAT4 data due to the roundoff error of converting from integers to LogEst and back to integers. check-in: 3c933bf9 user: drh tags: trunk
Changes
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Changes to src/analyze.c.

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    rc = sqlite3_exec(db, zSql, analysisLoader, &sInfo, 0);
    sqlite3DbFree(db, zSql);
  }


  /* Load the statistics from the sqlite_stat4 table. */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
  if( rc==SQLITE_OK ){
    int lookasideEnabled = db->lookaside.bEnabled;
    db->lookaside.bEnabled = 0;
    rc = loadStat4(db, sInfo.zDatabase);
    db->lookaside.bEnabled = lookasideEnabled;
  }
  for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){
    Index *pIdx = sqliteHashData(i);







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    rc = sqlite3_exec(db, zSql, analysisLoader, &sInfo, 0);
    sqlite3DbFree(db, zSql);
  }


  /* Load the statistics from the sqlite_stat4 table. */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
  if( rc==SQLITE_OK && OptimizationEnabled(db, SQLITE_Stat34) ){
    int lookasideEnabled = db->lookaside.bEnabled;
    db->lookaside.bEnabled = 0;
    rc = loadStat4(db, sInfo.zDatabase);
    db->lookaside.bEnabled = lookasideEnabled;
  }
  for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){
    Index *pIdx = sqliteHashData(i);

Changes to src/sqliteInt.h.

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/*                not used    0x0010   // Was: SQLITE_IdxRealAsInt */
#define SQLITE_DistinctOpt    0x0020   /* DISTINCT using indexes */
#define SQLITE_CoverIdxScan   0x0040   /* Covering index scans */
#define SQLITE_OrderByIdxJoin 0x0080   /* ORDER BY of joins via index */
#define SQLITE_SubqCoroutine  0x0100   /* Evaluate subqueries as coroutines */
#define SQLITE_Transitive     0x0200   /* Transitive constraints */
#define SQLITE_OmitNoopJoin   0x0400   /* Omit unused tables in joins */
#define SQLITE_Stat3          0x0800   /* Use the SQLITE_STAT3 table */
#define SQLITE_AllOpts        0xffff   /* All optimizations */

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







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/*                not used    0x0010   // Was: SQLITE_IdxRealAsInt */
#define SQLITE_DistinctOpt    0x0020   /* DISTINCT using indexes */
#define SQLITE_CoverIdxScan   0x0040   /* Covering index scans */
#define SQLITE_OrderByIdxJoin 0x0080   /* ORDER BY of joins via index */
#define SQLITE_SubqCoroutine  0x0100   /* Evaluate subqueries as coroutines */
#define SQLITE_Transitive     0x0200   /* Transitive constraints */
#define SQLITE_OmitNoopJoin   0x0400   /* Omit unused tables in joins */
#define SQLITE_Stat34         0x0800   /* Use STAT3 or STAT4 data */
#define SQLITE_AllOpts        0xffff   /* All optimizations */

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

Changes to src/test1.c.

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    { "factor-constants",    SQLITE_FactorOutConst },
    { "distinct-opt",        SQLITE_DistinctOpt    },
    { "cover-idx-scan",      SQLITE_CoverIdxScan   },
    { "order-by-idx-join",   SQLITE_OrderByIdxJoin },
    { "transitive",          SQLITE_Transitive     },
    { "subquery-coroutine",  SQLITE_SubqCoroutine  },
    { "omit-noop-join",      SQLITE_OmitNoopJoin   },
    { "stat3",               SQLITE_Stat3          },

  };

  if( objc!=4 ){
    Tcl_WrongNumArgs(interp, 1, objv, "DB OPT BOOLEAN");
    return TCL_ERROR;
  }
  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;







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    { "factor-constants",    SQLITE_FactorOutConst },
    { "distinct-opt",        SQLITE_DistinctOpt    },
    { "cover-idx-scan",      SQLITE_CoverIdxScan   },
    { "order-by-idx-join",   SQLITE_OrderByIdxJoin },
    { "transitive",          SQLITE_Transitive     },
    { "subquery-coroutine",  SQLITE_SubqCoroutine  },
    { "omit-noop-join",      SQLITE_OmitNoopJoin   },
    { "stat3",               SQLITE_Stat34         },
    { "stat4",               SQLITE_Stat34         },
  };

  if( objc!=4 ){
    Tcl_WrongNumArgs(interp, 1, objv, "DB OPT BOOLEAN");
    return TCL_ERROR;
  }
  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;

Changes to src/where.c.

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  ** TERM_VNULL tag will suppress the not-null check at the beginning
  ** of the loop.  Without the TERM_VNULL flag, the not-null check at
  ** the start of the loop will prevent any results from being returned.
  */
  if( pExpr->op==TK_NOTNULL
   && pExpr->pLeft->op==TK_COLUMN
   && pExpr->pLeft->iColumn>=0
   && OptimizationEnabled(db, SQLITE_Stat3)
  ){
    Expr *pNewExpr;
    Expr *pLeft = pExpr->pLeft;
    int idxNew;
    WhereTerm *pNewTerm;

    pNewExpr = sqlite3PExpr(pParse, TK_GT,
................................................................................

#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
  Index *p = pLoop->u.btree.pIndex;
  int nEq = pLoop->u.btree.nEq;

  if( p->nSample>0
   && nEq<p->nSampleCol
   && OptimizationEnabled(pParse->db, SQLITE_Stat3) 
  ){
    if( nEq==pBuilder->nRecValid ){
      UnpackedRecord *pRec = pBuilder->pRec;
      tRowcnt a[2];
      u8 aff;

      /* Variable iLower will be set to the estimate of the number of rows in 
................................................................................
        pNew->nOut -= nIn;
      }else{
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
        tRowcnt nOut = 0;
        if( nInMul==0 
         && pProbe->nSample 
         && pNew->u.btree.nEq<=pProbe->nSampleCol
         && OptimizationEnabled(db, SQLITE_Stat3) 
         && ((eOp & WO_IN)==0 || !ExprHasProperty(pTerm->pExpr, EP_xIsSelect))
        ){
          Expr *pExpr = pTerm->pExpr;
          if( (eOp & (WO_EQ|WO_ISNULL))!=0 ){
            testcase( eOp & WO_EQ );
            testcase( eOp & WO_ISNULL );
            rc = whereEqualScanEst(pParse, pBuilder, pExpr->pRight, &nOut);







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  ** TERM_VNULL tag will suppress the not-null check at the beginning
  ** of the loop.  Without the TERM_VNULL flag, the not-null check at
  ** the start of the loop will prevent any results from being returned.
  */
  if( pExpr->op==TK_NOTNULL
   && pExpr->pLeft->op==TK_COLUMN
   && pExpr->pLeft->iColumn>=0
   && OptimizationEnabled(db, SQLITE_Stat34)
  ){
    Expr *pNewExpr;
    Expr *pLeft = pExpr->pLeft;
    int idxNew;
    WhereTerm *pNewTerm;

    pNewExpr = sqlite3PExpr(pParse, TK_GT,
................................................................................

#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
  Index *p = pLoop->u.btree.pIndex;
  int nEq = pLoop->u.btree.nEq;

  if( p->nSample>0
   && nEq<p->nSampleCol

  ){
    if( nEq==pBuilder->nRecValid ){
      UnpackedRecord *pRec = pBuilder->pRec;
      tRowcnt a[2];
      u8 aff;

      /* Variable iLower will be set to the estimate of the number of rows in 
................................................................................
        pNew->nOut -= nIn;
      }else{
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
        tRowcnt nOut = 0;
        if( nInMul==0 
         && pProbe->nSample 
         && pNew->u.btree.nEq<=pProbe->nSampleCol

         && ((eOp & WO_IN)==0 || !ExprHasProperty(pTerm->pExpr, EP_xIsSelect))
        ){
          Expr *pExpr = pTerm->pExpr;
          if( (eOp & (WO_EQ|WO_ISNULL))!=0 ){
            testcase( eOp & WO_EQ );
            testcase( eOp & WO_ISNULL );
            rc = whereEqualScanEst(pParse, pBuilder, pExpr->pRight, &nOut);