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Overview
SHA1:559733b09e9630fac9d9318a7ecbaba9134e9160
Date: 2016-05-20 14:11:37
User: drh
Comment:For queries with both ORDER BY and LIMIT, if the rows of the inner loop are emitted in ORDER BY order and the LIMIT has been reached, then optimize by exiting the inner loop and continuing with the next cycle of the first outer loop.
References
2016-10-12
14:00 • New ticket [96c1454c] Incorrect result with ORDER BY DESC and LIMIT (again). (user: drh)
2016-09-07
00:42 • New ticket [0c4df461] Incorrect result with ORDER BY DESC and LIMIT. (user: drh)
Tags And Properties
Context
2016-05-20
14:54
[9033afbb] Optimizations to link list merge sort code in vdbesort.c, pcache.c, and rowset.c. Resulting binaries are 10 bytes smaller and use 0.03% fewer CPU cycles. (user: drh, tags: trunk)
14:11
[559733b0] For queries with both ORDER BY and LIMIT, if the rows of the inner loop are emitted in ORDER BY order and the LIMIT has been reached, then optimize by exiting the inner loop and continuing with the next cycle of the first outer loop. (user: drh, tags: trunk)
13:44
[ed1b30dc] Closed-Leaf: Set the NULLEQ flag on the sequence counter comparison in the ORDER BY LIMIT optimization, to avoid coverage complaints about not testing the NULL case. (user: drh, tags: orderby-limit)
12:22
[645bd696] Autoconf configure.ac adjustment to try to get it to look for both editline and readline automatically. (user: drh, tags: trunk)
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/select.c.

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  int nOBSat;           /* Number of ORDER BY terms satisfied by indices */
  int iECursor;         /* Cursor number for the sorter */
  int regReturn;        /* Register holding block-output return address */
  int labelBkOut;       /* Start label for the block-output subroutine */
  int addrSortIndex;    /* Address of the OP_SorterOpen or OP_OpenEphemeral */
  int labelDone;        /* Jump here when done, ex: LIMIT reached */
  u8 sortFlags;         /* Zero or more SORTFLAG_* bits */

};
#define SORTFLAG_UseSorter  0x01   /* Use SorterOpen instead of OpenEphemeral */

/*
** Delete all the content of a Select structure.  Deallocate the structure
** itself only if bFree is true.
*/
................................................................................
    op = OP_SorterInsert;
  }else{
    op = OP_IdxInsert;
  }
  sqlite3VdbeAddOp2(v, op, pSort->iECursor, regRecord);
  if( iLimit ){
    int addr;





    addr = sqlite3VdbeAddOp3(v, OP_IfNotZero, iLimit, 0, 1); VdbeCoverage(v);
    sqlite3VdbeAddOp1(v, OP_Last, pSort->iECursor);





    sqlite3VdbeAddOp1(v, OP_Delete, pSort->iECursor);











    sqlite3VdbeJumpHere(v, addr);
  }
}

/*
** Add code to implement the OFFSET
*/
................................................................................
      p->nSelectRow = sqlite3WhereOutputRowCount(pWInfo);
    }
    if( sDistinct.isTnct && sqlite3WhereIsDistinct(pWInfo) ){
      sDistinct.eTnctType = sqlite3WhereIsDistinct(pWInfo);
    }
    if( sSort.pOrderBy ){
      sSort.nOBSat = sqlite3WhereIsOrdered(pWInfo);

      if( sSort.nOBSat==sSort.pOrderBy->nExpr ){
        sSort.pOrderBy = 0;
      }
    }

    /* If sorting index that was created by a prior OP_OpenEphemeral 
    ** instruction ended up not being needed, then change the OP_OpenEphemeral







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  int nOBSat;           /* Number of ORDER BY terms satisfied by indices */
  int iECursor;         /* Cursor number for the sorter */
  int regReturn;        /* Register holding block-output return address */
  int labelBkOut;       /* Start label for the block-output subroutine */
  int addrSortIndex;    /* Address of the OP_SorterOpen or OP_OpenEphemeral */
  int labelDone;        /* Jump here when done, ex: LIMIT reached */
  u8 sortFlags;         /* Zero or more SORTFLAG_* bits */
  u8 bOrderedInnerLoop; /* ORDER BY correctly sorts the inner loop */
};
#define SORTFLAG_UseSorter  0x01   /* Use SorterOpen instead of OpenEphemeral */

/*
** Delete all the content of a Select structure.  Deallocate the structure
** itself only if bFree is true.
*/
................................................................................
    op = OP_SorterInsert;
  }else{
    op = OP_IdxInsert;
  }
  sqlite3VdbeAddOp2(v, op, pSort->iECursor, regRecord);
  if( iLimit ){
    int addr;
    int r1 = 0;
    /* Fill the sorter until it contains LIMIT+OFFSET entries.  (The iLimit
    ** register is initialized with value of LIMIT+OFFSET.)  After the sorter
    ** fills up, delete the least entry in the sorter after each insert.
    ** Thus we never hold more than the LIMIT+OFFSET rows in memory at once */
    addr = sqlite3VdbeAddOp3(v, OP_IfNotZero, iLimit, 0, 1); VdbeCoverage(v);
    sqlite3VdbeAddOp1(v, OP_Last, pSort->iECursor);
    if( pSort->bOrderedInnerLoop ){
      r1 = ++pParse->nMem;
      sqlite3VdbeAddOp3(v, OP_Column, pSort->iECursor, nExpr, r1);
      VdbeComment((v, "seq"));
    }
    sqlite3VdbeAddOp1(v, OP_Delete, pSort->iECursor);
    if( pSort->bOrderedInnerLoop ){
      /* If the inner loop is driven by an index such that values from
      ** the same iteration of the inner loop are in sorted order, then
      ** immediately jump to the next iteration of an inner loop if the
      ** entry from the current iteration does not fit into the top
      ** LIMIT+OFFSET entries of the sorter. */
      int iBrk = sqlite3VdbeCurrentAddr(v) + 2;
      sqlite3VdbeAddOp3(v, OP_Eq, regBase+nExpr, iBrk, r1);
      sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
      VdbeCoverage(v);
    }
    sqlite3VdbeJumpHere(v, addr);
  }
}

/*
** Add code to implement the OFFSET
*/
................................................................................
      p->nSelectRow = sqlite3WhereOutputRowCount(pWInfo);
    }
    if( sDistinct.isTnct && sqlite3WhereIsDistinct(pWInfo) ){
      sDistinct.eTnctType = sqlite3WhereIsDistinct(pWInfo);
    }
    if( sSort.pOrderBy ){
      sSort.nOBSat = sqlite3WhereIsOrdered(pWInfo);
      sSort.bOrderedInnerLoop = sqlite3WhereOrderedInnerLoop(pWInfo);
      if( sSort.nOBSat==sSort.pOrderBy->nExpr ){
        sSort.pOrderBy = 0;
      }
    }

    /* If sorting index that was created by a prior OP_OpenEphemeral 
    ** instruction ended up not being needed, then change the OP_OpenEphemeral

Changes to src/sqliteInt.h.

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#define WHERE_OR_SUBCLAUSE     0x0020 /* Processing a sub-WHERE as part of
                                      ** the OR optimization  */
#define WHERE_GROUPBY          0x0040 /* pOrderBy is really a GROUP BY */
#define WHERE_DISTINCTBY       0x0080 /* pOrderby is really a DISTINCT clause */
#define WHERE_WANT_DISTINCT    0x0100 /* All output needs to be distinct */
#define WHERE_SORTBYGROUP      0x0200 /* Support sqlite3WhereIsSorted() */
#define WHERE_SEEK_TABLE       0x0400 /* Do not defer seeks on main table */
                        /*     0x0800    not currently used */
                        /*     0x1000    not currently used */
                        /*     0x2000    not currently used */
#define WHERE_USE_LIMIT        0x4000 /* Use the LIMIT in cost estimates */
                        /*     0x8000    not currently used */

/* Allowed return values from sqlite3WhereIsDistinct()
*/
................................................................................
void sqlite3DeleteFrom(Parse*, SrcList*, Expr*);
void sqlite3Update(Parse*, SrcList*, ExprList*, Expr*, int);
WhereInfo *sqlite3WhereBegin(Parse*,SrcList*,Expr*,ExprList*,ExprList*,u16,int);
void sqlite3WhereEnd(WhereInfo*);
LogEst sqlite3WhereOutputRowCount(WhereInfo*);
int sqlite3WhereIsDistinct(WhereInfo*);
int sqlite3WhereIsOrdered(WhereInfo*);

int sqlite3WhereIsSorted(WhereInfo*);
int sqlite3WhereContinueLabel(WhereInfo*);
int sqlite3WhereBreakLabel(WhereInfo*);
int sqlite3WhereOkOnePass(WhereInfo*, int*);
#define ONEPASS_OFF      0        /* Use of ONEPASS not allowed */
#define ONEPASS_SINGLE   1        /* ONEPASS valid for a single row update */
#define ONEPASS_MULTI    2        /* ONEPASS is valid for multiple rows */







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#define WHERE_OR_SUBCLAUSE     0x0020 /* Processing a sub-WHERE as part of
                                      ** the OR optimization  */
#define WHERE_GROUPBY          0x0040 /* pOrderBy is really a GROUP BY */
#define WHERE_DISTINCTBY       0x0080 /* pOrderby is really a DISTINCT clause */
#define WHERE_WANT_DISTINCT    0x0100 /* All output needs to be distinct */
#define WHERE_SORTBYGROUP      0x0200 /* Support sqlite3WhereIsSorted() */
#define WHERE_SEEK_TABLE       0x0400 /* Do not defer seeks on main table */
#define WHERE_ORDERBY_LIMIT    0x0800 /* ORDERBY+LIMIT on the inner loop */
                        /*     0x1000    not currently used */
                        /*     0x2000    not currently used */
#define WHERE_USE_LIMIT        0x4000 /* Use the LIMIT in cost estimates */
                        /*     0x8000    not currently used */

/* Allowed return values from sqlite3WhereIsDistinct()
*/
................................................................................
void sqlite3DeleteFrom(Parse*, SrcList*, Expr*);
void sqlite3Update(Parse*, SrcList*, ExprList*, Expr*, int);
WhereInfo *sqlite3WhereBegin(Parse*,SrcList*,Expr*,ExprList*,ExprList*,u16,int);
void sqlite3WhereEnd(WhereInfo*);
LogEst sqlite3WhereOutputRowCount(WhereInfo*);
int sqlite3WhereIsDistinct(WhereInfo*);
int sqlite3WhereIsOrdered(WhereInfo*);
int sqlite3WhereOrderedInnerLoop(WhereInfo*);
int sqlite3WhereIsSorted(WhereInfo*);
int sqlite3WhereContinueLabel(WhereInfo*);
int sqlite3WhereBreakLabel(WhereInfo*);
int sqlite3WhereOkOnePass(WhereInfo*, int*);
#define ONEPASS_OFF      0        /* Use of ONEPASS not allowed */
#define ONEPASS_SINGLE   1        /* ONEPASS valid for a single row update */
#define ONEPASS_MULTI    2        /* ONEPASS is valid for multiple rows */

Changes to src/where.c.

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/*
** Return TRUE if the WHERE clause returns rows in ORDER BY order.
** Return FALSE if the output needs to be sorted.
*/
int sqlite3WhereIsOrdered(WhereInfo *pWInfo){
  return pWInfo->nOBSat;
}













/*
** Return the VDBE address or label to jump to in order to continue
** immediately with the next row of a WHERE clause.
*/
int sqlite3WhereContinueLabel(WhereInfo *pWInfo){
  assert( pWInfo->iContinue!=0 );
................................................................................
** the pOrderBy terms can be matched in any order.  With ORDER BY, the 
** pOrderBy terms must be matched in strict left-to-right order.
*/
static i8 wherePathSatisfiesOrderBy(
  WhereInfo *pWInfo,    /* The WHERE clause */
  ExprList *pOrderBy,   /* ORDER BY or GROUP BY or DISTINCT clause to check */
  WherePath *pPath,     /* The WherePath to check */
  u16 wctrlFlags,       /* Might contain WHERE_GROUPBY or WHERE_DISTINCTBY */
  u16 nLoop,            /* Number of entries in pPath->aLoop[] */
  WhereLoop *pLast,     /* Add this WhereLoop to the end of pPath->aLoop[] */
  Bitmask *pRevMask     /* OUT: Mask of WhereLoops to run in reverse order */
){
  u8 revSet;            /* True if rev is known */
  u8 rev;               /* Composite sort order */
  u8 revIdx;            /* Index sort order */
  u8 isOrderDistinct;   /* All prior WhereLoops are order-distinct */
  u8 distinctColumns;   /* True if the loop has UNIQUE NOT NULL columns */
  u8 isMatch;           /* iColumn matches a term of the ORDER BY clause */

  u16 nKeyCol;          /* Number of key columns in pIndex */
  u16 nColumn;          /* Total number of ordered columns in the index */
  u16 nOrderBy;         /* Number terms in the ORDER BY clause */
  int iLoop;            /* Index of WhereLoop in pPath being processed */
  int i, j;             /* Loop counters */
  int iCur;             /* Cursor number for current WhereLoop */
  int iColumn;          /* A column number within table iCur */
................................................................................
  nOrderBy = pOrderBy->nExpr;
  testcase( nOrderBy==BMS-1 );
  if( nOrderBy>BMS-1 ) return 0;  /* Cannot optimize overly large ORDER BYs */
  isOrderDistinct = 1;
  obDone = MASKBIT(nOrderBy)-1;
  orderDistinctMask = 0;
  ready = 0;


  for(iLoop=0; isOrderDistinct && obSat<obDone && iLoop<=nLoop; iLoop++){
    if( iLoop>0 ) ready |= pLoop->maskSelf;

    pLoop = iLoop<nLoop ? pPath->aLoop[iLoop] : pLast;




    if( pLoop->wsFlags & WHERE_VIRTUALTABLE ){
      if( pLoop->u.vtab.isOrdered ) obSat = obDone;
      break;
    }
    iCur = pWInfo->pTabList->a[pLoop->iTab].iCursor;

    /* Mark off any ORDER BY term X that is a column in the table of
................................................................................
    */
    for(i=0; i<nOrderBy; i++){
      if( MASKBIT(i) & obSat ) continue;
      pOBExpr = sqlite3ExprSkipCollate(pOrderBy->a[i].pExpr);
      if( pOBExpr->op!=TK_COLUMN ) continue;
      if( pOBExpr->iTable!=iCur ) continue;
      pTerm = sqlite3WhereFindTerm(&pWInfo->sWC, iCur, pOBExpr->iColumn,
                       ~ready, WO_EQ|WO_ISNULL|WO_IS, 0);
      if( pTerm==0 ) continue;
      if( (pTerm->eOperator&(WO_EQ|WO_IS))!=0 && pOBExpr->iColumn>=0 ){
        const char *z1, *z2;
        pColl = sqlite3ExprCollSeq(pWInfo->pParse, pOrderBy->a[i].pExpr);
        if( !pColl ) pColl = db->pDfltColl;
        z1 = pColl->zName;
        pColl = sqlite3ExprCollSeq(pWInfo->pParse, pTerm->pExpr);
................................................................................
      ** that are not constrained by == or IN.
      */
      rev = revSet = 0;
      distinctColumns = 0;
      for(j=0; j<nColumn; j++){
        u8 bOnce;   /* True to run the ORDER BY search loop */

        /* Skip over == and IS NULL terms */


        if( j<pLoop->u.btree.nEq
         && pLoop->nSkip==0
         && ((i = pLoop->aLTerm[j]->eOperator) & (WO_EQ|WO_ISNULL|WO_IS))!=0
        ){
          if( i & WO_ISNULL ){
            testcase( isOrderDistinct );
            isOrderDistinct = 0;
          }
          continue;  
        }
................................................................................
  if( pWInfo->pOrderBy ){
    if( pWInfo->wctrlFlags & WHERE_DISTINCTBY ){
      if( pFrom->isOrdered==pWInfo->pOrderBy->nExpr ){
        pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
      }
    }else{
      pWInfo->nOBSat = pFrom->isOrdered;


      if( pWInfo->nOBSat<0 ) pWInfo->nOBSat = 0;






      pWInfo->revMask = pFrom->revLoop;



    }
    if( (pWInfo->wctrlFlags & WHERE_SORTBYGROUP)
        && pWInfo->nOBSat==pWInfo->pOrderBy->nExpr && nLoop>0
    ){
      Bitmask revMask = 0;
      int nOrder = wherePathSatisfiesOrderBy(pWInfo, pWInfo->pOrderBy, 
          pFrom, 0, nLoop-1, pFrom->aLoop[nLoop-1], &revMask







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/*
** Return TRUE if the WHERE clause returns rows in ORDER BY order.
** Return FALSE if the output needs to be sorted.
*/
int sqlite3WhereIsOrdered(WhereInfo *pWInfo){
  return pWInfo->nOBSat;
}

/*
** Return TRUE if the innermost loop of the WHERE clause implementation
** returns rows in ORDER BY order for complete run of the inner loop.
**
** Across multiple iterations of outer loops, the output rows need not be
** sorted.  As long as rows are sorted for just the innermost loop, this
** routine can return TRUE.
*/
int sqlite3WhereOrderedInnerLoop(WhereInfo *pWInfo){
  return pWInfo->bOrderedInnerLoop;
}

/*
** Return the VDBE address or label to jump to in order to continue
** immediately with the next row of a WHERE clause.
*/
int sqlite3WhereContinueLabel(WhereInfo *pWInfo){
  assert( pWInfo->iContinue!=0 );
................................................................................
** the pOrderBy terms can be matched in any order.  With ORDER BY, the 
** pOrderBy terms must be matched in strict left-to-right order.
*/
static i8 wherePathSatisfiesOrderBy(
  WhereInfo *pWInfo,    /* The WHERE clause */
  ExprList *pOrderBy,   /* ORDER BY or GROUP BY or DISTINCT clause to check */
  WherePath *pPath,     /* The WherePath to check */
  u16 wctrlFlags,       /* WHERE_GROUPBY or _DISTINCTBY or _ORDERBY_LIMIT */
  u16 nLoop,            /* Number of entries in pPath->aLoop[] */
  WhereLoop *pLast,     /* Add this WhereLoop to the end of pPath->aLoop[] */
  Bitmask *pRevMask     /* OUT: Mask of WhereLoops to run in reverse order */
){
  u8 revSet;            /* True if rev is known */
  u8 rev;               /* Composite sort order */
  u8 revIdx;            /* Index sort order */
  u8 isOrderDistinct;   /* All prior WhereLoops are order-distinct */
  u8 distinctColumns;   /* True if the loop has UNIQUE NOT NULL columns */
  u8 isMatch;           /* iColumn matches a term of the ORDER BY clause */
  u16 eqOpMask;         /* Allowed equality operators */
  u16 nKeyCol;          /* Number of key columns in pIndex */
  u16 nColumn;          /* Total number of ordered columns in the index */
  u16 nOrderBy;         /* Number terms in the ORDER BY clause */
  int iLoop;            /* Index of WhereLoop in pPath being processed */
  int i, j;             /* Loop counters */
  int iCur;             /* Cursor number for current WhereLoop */
  int iColumn;          /* A column number within table iCur */
................................................................................
  nOrderBy = pOrderBy->nExpr;
  testcase( nOrderBy==BMS-1 );
  if( nOrderBy>BMS-1 ) return 0;  /* Cannot optimize overly large ORDER BYs */
  isOrderDistinct = 1;
  obDone = MASKBIT(nOrderBy)-1;
  orderDistinctMask = 0;
  ready = 0;
  eqOpMask = WO_EQ | WO_IS | WO_ISNULL;
  if( wctrlFlags & WHERE_ORDERBY_LIMIT ) eqOpMask |= WO_IN;
  for(iLoop=0; isOrderDistinct && obSat<obDone && iLoop<=nLoop; iLoop++){
    if( iLoop>0 ) ready |= pLoop->maskSelf;
    if( iLoop<nLoop ){
      pLoop = pPath->aLoop[iLoop];
      if( wctrlFlags & WHERE_ORDERBY_LIMIT ) continue;
    }else{
      pLoop = pLast;
    }
    if( pLoop->wsFlags & WHERE_VIRTUALTABLE ){
      if( pLoop->u.vtab.isOrdered ) obSat = obDone;
      break;
    }
    iCur = pWInfo->pTabList->a[pLoop->iTab].iCursor;

    /* Mark off any ORDER BY term X that is a column in the table of
................................................................................
    */
    for(i=0; i<nOrderBy; i++){
      if( MASKBIT(i) & obSat ) continue;
      pOBExpr = sqlite3ExprSkipCollate(pOrderBy->a[i].pExpr);
      if( pOBExpr->op!=TK_COLUMN ) continue;
      if( pOBExpr->iTable!=iCur ) continue;
      pTerm = sqlite3WhereFindTerm(&pWInfo->sWC, iCur, pOBExpr->iColumn,
                       ~ready, eqOpMask, 0);
      if( pTerm==0 ) continue;
      if( (pTerm->eOperator&(WO_EQ|WO_IS))!=0 && pOBExpr->iColumn>=0 ){
        const char *z1, *z2;
        pColl = sqlite3ExprCollSeq(pWInfo->pParse, pOrderBy->a[i].pExpr);
        if( !pColl ) pColl = db->pDfltColl;
        z1 = pColl->zName;
        pColl = sqlite3ExprCollSeq(pWInfo->pParse, pTerm->pExpr);
................................................................................
      ** that are not constrained by == or IN.
      */
      rev = revSet = 0;
      distinctColumns = 0;
      for(j=0; j<nColumn; j++){
        u8 bOnce;   /* True to run the ORDER BY search loop */

        /* Skip over == and IS and ISNULL terms.
        ** (Also skip IN terms when doing WHERE_ORDERBY_LIMIT processing)
        */
        if( j<pLoop->u.btree.nEq
         && pLoop->nSkip==0
         && ((i = pLoop->aLTerm[j]->eOperator) & eqOpMask)!=0
        ){
          if( i & WO_ISNULL ){
            testcase( isOrderDistinct );
            isOrderDistinct = 0;
          }
          continue;  
        }
................................................................................
  if( pWInfo->pOrderBy ){
    if( pWInfo->wctrlFlags & WHERE_DISTINCTBY ){
      if( pFrom->isOrdered==pWInfo->pOrderBy->nExpr ){
        pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
      }
    }else{
      pWInfo->nOBSat = pFrom->isOrdered;
      pWInfo->revMask = pFrom->revLoop;
      if( pWInfo->nOBSat<=0 ){
        pWInfo->nOBSat = 0;
        if( nLoop>0 ){
          Bitmask m;
          int rc = wherePathSatisfiesOrderBy(pWInfo, pWInfo->pOrderBy, pFrom,
                      WHERE_ORDERBY_LIMIT, nLoop-1, pFrom->aLoop[nLoop-1], &m);
          if( rc==pWInfo->pOrderBy->nExpr ){
            pWInfo->bOrderedInnerLoop = 1;
            pWInfo->revMask = m;
          }
        }
      }
    }
    if( (pWInfo->wctrlFlags & WHERE_SORTBYGROUP)
        && pWInfo->nOBSat==pWInfo->pOrderBy->nExpr && nLoop>0
    ){
      Bitmask revMask = 0;
      int nOrder = wherePathSatisfiesOrderBy(pWInfo, pWInfo->pOrderBy, 
          pFrom, 0, nLoop-1, pFrom->aLoop[nLoop-1], &revMask

Changes to src/whereInt.h.

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  LogEst nRowOut;           /* Estimated number of output rows */
  LogEst iLimit;            /* LIMIT if wctrlFlags has WHERE_USE_LIMIT */
  u16 wctrlFlags;           /* Flags originally passed to sqlite3WhereBegin() */
  i8 nOBSat;                /* Number of ORDER BY terms satisfied by indices */
  u8 sorted;                /* True if really sorted (not just grouped) */
  u8 eOnePass;              /* ONEPASS_OFF, or _SINGLE, or _MULTI */
  u8 untestedTerms;         /* Not all WHERE terms resolved by outer loop */
  u8 eDistinct;             /* One of the WHERE_DISTINCT_* values below */
  u8 nLevel;                /* Number of nested loop */

  int iTop;                 /* The very beginning of the WHERE loop */
  int iContinue;            /* Jump here to continue with next record */
  int iBreak;               /* Jump here to break out of the loop */
  int savedNQueryLoop;      /* pParse->nQueryLoop outside the WHERE loop */
  int aiCurOnePass[2];      /* OP_OpenWrite cursors for the ONEPASS opt */
  WhereMaskSet sMaskSet;    /* Map cursor numbers to bitmasks */
  WhereClause sWC;          /* Decomposition of the WHERE clause */







|

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  LogEst nRowOut;           /* Estimated number of output rows */
  LogEst iLimit;            /* LIMIT if wctrlFlags has WHERE_USE_LIMIT */
  u16 wctrlFlags;           /* Flags originally passed to sqlite3WhereBegin() */
  i8 nOBSat;                /* Number of ORDER BY terms satisfied by indices */
  u8 sorted;                /* True if really sorted (not just grouped) */
  u8 eOnePass;              /* ONEPASS_OFF, or _SINGLE, or _MULTI */
  u8 untestedTerms;         /* Not all WHERE terms resolved by outer loop */
  u8 eDistinct;             /* One of the WHERE_DISTINCT_* values */
  u8 nLevel;                /* Number of nested loop */
  u8 bOrderedInnerLoop;     /* True if only the inner-most loop is ordered */
  int iTop;                 /* The very beginning of the WHERE loop */
  int iContinue;            /* Jump here to continue with next record */
  int iBreak;               /* Jump here to break out of the loop */
  int savedNQueryLoop;      /* pParse->nQueryLoop outside the WHERE loop */
  int aiCurOnePass[2];      /* OP_OpenWrite cursors for the ONEPASS opt */
  WhereMaskSet sMaskSet;    /* Map cursor numbers to bitmasks */
  WhereClause sWC;          /* Decomposition of the WHERE clause */

Added test/limit2.test.





































































































































































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# 2016-05-20
#
# 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.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is testing the LIMIT in combination with ORDER BY
# and in particular, the optimizations in the inner loop that cause an
# early exit of the inner loop when the LIMIT is reached and the inner
# loop is emitting rows in ORDER BY order.


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

do_execsql_test limit2-100 {
  CREATE TABLE t1(a,b);
  WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<1000)
    INSERT INTO t1(a,b) SELECT 1, (x*17)%1000 + 1000 FROM c;
  INSERT INTO t1(a,b) VALUES(2,2),(3,1006),(4,4),(5,9999);
  CREATE INDEX t1ab ON t1(a,b);
}
set sqlite_search_count 0
do_execsql_test limit2-100.1 {
  SELECT a, b, '|' FROM t1 WHERE a IN (2,4,5,3,1) ORDER BY b LIMIT 5;
} {2 2 | 4 4 | 1 1000 | 1 1001 | 1 1002 |}
set fast_count $sqlite_search_count
set sqlite_search_count 0
do_execsql_test limit2-100.2 {
  SELECT a, b, '|' FROM t1 WHERE a IN (2,4,5,3,1) ORDER BY +b LIMIT 5;
} {2 2 | 4 4 | 1 1000 | 1 1001 | 1 1002 |}
do_test limit2-100.3 {
  set slow_count $sqlite_search_count
  expr {$fast_count < 0.02*$slow_count}
} {1}

do_execsql_test limit2-110 {
  CREATE TABLE t2(x,y);
  INSERT INTO t2(x,y) VALUES('a',1),('a',2),('a',3),('a',4);
  INSERT INTO t2(x,y) VALUES('b',1),('c',2),('d',3),('e',4);
  CREATE INDEX t2xy ON t2(x,y);
}
set sqlite_search_count 0
do_execsql_test limit2-110.1 {
  SELECT a, b, '|' FROM t2, t1 WHERE t2.x='a' AND t1.a=t2.y ORDER BY t1.b LIMIT 5;
} {2 2 | 4 4 | 1 1000 | 1 1001 | 1 1002 |}
set fast_count $sqlite_search_count
set sqlite_search_count 0
do_execsql_test limit2-110.2 {
  SELECT a, b, '|' FROM t2, t1 WHERE t2.x='a' AND t1.a=t2.y ORDER BY +t1.b LIMIT 5;
} {2 2 | 4 4 | 1 1000 | 1 1001 | 1 1002 |}
set slow_count $sqlite_search_count
do_test limit2-110.3 {
  expr {$fast_count < 0.02*$slow_count}
} {1}

do_execsql_test limit2-120 {
  DROP INDEX t1ab;
  CREATE INDEX t1ab ON t1(a,b DESC);
}
set sqlite_search_count 0
do_execsql_test limit2-120.1 {
  SELECT a, b, '|' FROM t1 WHERE a IN (2,4,5,3,1) ORDER BY b DESC LIMIT 5;
} {5 9999 | 1 1999 | 1 1998 | 1 1997 | 1 1996 |}
set fast_count $sqlite_search_count
set sqlite_search_count 0
do_execsql_test limit2-120.2 {
  SELECT a, b, '|' FROM t1 WHERE a IN (2,4,5,3,1) ORDER BY +b DESC LIMIT 5;
} {5 9999 | 1 1999 | 1 1998 | 1 1997 | 1 1996 |}
do_test limit2-120.3 {
  set slow_count $sqlite_search_count
  expr {$fast_count < 0.02*$slow_count}
} {1}



finish_test