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Overview
Comment:Improved ORDER BY optimization for WITHOUT ROWID tables.
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Timelines: family | ancestors | descendants | both | omit-rowid
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SHA1: 8f1709ff2d52d5ceca3da6a2a4e06da204d9e65a
User & Date: drh 2013-11-06 12:56:04
Context
2013-11-06
14:05
Minor optimization to the OP_Halt opcode. check-in: d70c7881 user: drh tags: omit-rowid
12:56
Improved ORDER BY optimization for WITHOUT ROWID tables. check-in: 8f1709ff user: drh tags: omit-rowid
12:05
Disable the OR optimization for WITHOUT ROWID tables, since it relies on the use of rowids. check-in: 6055dad2 user: drh tags: omit-rowid
Changes
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Changes to src/where.c.

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){
  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 columns in pIndex */

  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 */
  WhereLoop *pLoop = 0; /* Current WhereLoop being processed. */
  WhereTerm *pTerm;     /* A single term of the WHERE clause */
................................................................................
      obSat |= MASKBIT(i);
    }

    if( (pLoop->wsFlags & WHERE_ONEROW)==0 ){
      if( pLoop->wsFlags & WHERE_IPK ){
        pIndex = 0;
        nKeyCol = 0;

      }else if( (pIndex = pLoop->u.btree.pIndex)==0 || pIndex->bUnordered ){
        return 0;
      }else{
        nKeyCol = pIndex->nKeyCol;



        isOrderDistinct = pIndex->onError!=OE_None;
      }

      /* Loop through all columns of the index and deal with the ones
      ** that are not constrained by == or IN.
      */
      rev = revSet = 0;
      distinctColumns = 0;
      for(j=0; j<=nKeyCol; j++){
        u8 bOnce;   /* True to run the ORDER BY search loop */

        /* Skip over == and IS NULL terms */
        if( j<pLoop->u.btree.nEq
         && ((i = pLoop->aLTerm[j]->eOperator) & (WO_EQ|WO_ISNULL))!=0
        ){
          if( i & WO_ISNULL ){
................................................................................
          }
          continue;  
        }

        /* Get the column number in the table (iColumn) and sort order
        ** (revIdx) for the j-th column of the index.
        */
        if( j<nKeyCol ){
          /* Normal index columns */
          iColumn = pIndex->aiColumn[j];
          revIdx = pIndex->aSortOrder[j];
          if( iColumn==pIndex->pTable->iPKey ) iColumn = -1;
        }else{
          /* The ROWID column at the end */
          assert( j==nKeyCol );
          iColumn = -1;
          revIdx = 0;
        }

        /* An unconstrained column that might be NULL means that this
        ** WhereLoop is not well-ordered 
        */







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){
  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 */
  WhereLoop *pLoop = 0; /* Current WhereLoop being processed. */
  WhereTerm *pTerm;     /* A single term of the WHERE clause */
................................................................................
      obSat |= MASKBIT(i);
    }

    if( (pLoop->wsFlags & WHERE_ONEROW)==0 ){
      if( pLoop->wsFlags & WHERE_IPK ){
        pIndex = 0;
        nKeyCol = 0;
        nColumn = 1;
      }else if( (pIndex = pLoop->u.btree.pIndex)==0 || pIndex->bUnordered ){
        return 0;
      }else{
        nKeyCol = pIndex->nKeyCol;
        nColumn = pIndex->nColumn;
        assert( nColumn==nKeyCol+1 || !HasRowid(pIndex->pTable) );
        assert( pIndex->aiColumn[nColumn-1]==(-1) || !HasRowid(pIndex->pTable));
        isOrderDistinct = pIndex->onError!=OE_None;
      }

      /* Loop through all columns of the index and deal with the ones
      ** 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
         && ((i = pLoop->aLTerm[j]->eOperator) & (WO_EQ|WO_ISNULL))!=0
        ){
          if( i & WO_ISNULL ){
................................................................................
          }
          continue;  
        }

        /* Get the column number in the table (iColumn) and sort order
        ** (revIdx) for the j-th column of the index.
        */
        if( pIndex ){

          iColumn = pIndex->aiColumn[j];
          revIdx = pIndex->aSortOrder[j];
          if( iColumn==pIndex->pTable->iPKey ) iColumn = -1;
        }else{


          iColumn = -1;
          revIdx = 0;
        }

        /* An unconstrained column that might be NULL means that this
        ** WhereLoop is not well-ordered
        */

Changes to test/orderby5.test.

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  SELECT * FROM t1 WHERE a=0 ORDER BY c, a, b;
} {/B-TREE/}
do_execsql_test 2.7 {
  EXPLAIN QUERY PLAN
  SELECT * FROM t1 WHERE a=0 ORDER BY c, b, a;
} {/B-TREE/}

















finish_test








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  SELECT * FROM t1 WHERE a=0 ORDER BY c, a, b;
} {/B-TREE/}
do_execsql_test 2.7 {
  EXPLAIN QUERY PLAN
  SELECT * FROM t1 WHERE a=0 ORDER BY c, b, a;
} {/B-TREE/}


do_execsql_test 3.0 {
  CREATE TABLE t3(a INTEGER PRIMARY KEY, b, c, d, e, f);
  CREATE INDEX t3bcde ON t3(b, c, d, e);
  EXPLAIN QUERY PLAN
  SELECT a FROM t3 WHERE b=2 AND c=3 ORDER BY d DESC, e DESC, b, c, a DESC;
} {~/B-TREE/}
do_execsql_test 3.1 {
  DROP TABLE t3;
  CREATE TABLE t3(a INTEGER PRIMARY KEY, b, c, d, e, f) WITHOUT rowid;
  CREATE INDEX t3bcde ON t3(b, c, d, e);
  EXPLAIN QUERY PLAN
  SELECT a FROM t3 WHERE b=2 AND c=3 ORDER BY d DESC, e DESC, b, c, a DESC;
} {~/B-TREE/}


finish_test