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Overview
Comment:When using an index to scan a database table, read column data from the index in preference to the table. This increases the likelihood that the table will not be required at all. (CVS 4580)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 061608c72ac0a96eacf3b64d638235e4739f96ba
User & Date: danielk1977 2007-11-29 17:43:28
Context
2007-11-29
18:36
Add the optional (and experimental) mmap() memory allocator in the mem4.c module. (CVS 4581) check-in: cfd683ac user: drh tags: trunk
17:43
When using an index to scan a database table, read column data from the index in preference to the table. This increases the likelihood that the table will not be required at all. (CVS 4580) check-in: 061608c7 user: danielk1977 tags: trunk
17:05
Optimisations for expressions of the form "<value> IN (SELECT <column> FROM )". (CVS 4579)
check-in: 56d0e326 user: danielk1977 tags: trunk
Changes
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Changes to src/where.c.

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** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is reponsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.264 2007/11/29 17:05:18 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
*/
#define BMS  (sizeof(Bitmask)*8)
................................................................................
    if( (pIx = pLevel->pIdx)!=0 ){
      KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
      assert( pIx->pSchema==pTab->pSchema );
      sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
      VdbeComment((v, "# %s", pIx->zName));
      sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum,
                     (char*)pKey, P3_KEYINFO_HANDOFF);
    }
    if( (pLevel->flags & (WHERE_IDX_ONLY|WHERE_COLUMN_RANGE))!=0 ){
      /* Only call OP_SetNumColumns on the index if we might later use
      ** OP_Column on the index. */
      sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1);
    }
    sqlite3CodeVerifySchema(pParse, iDb);
  }
  pWInfo->iTop = sqlite3VdbeCurrentAddr(v);

  /* Generate the code to do the search.  Each iteration of the for
................................................................................
    if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
      sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0);
    }
    if( pLevel->pIdx!=0 ){
      sqlite3VdbeAddOp(v, OP_Close, pLevel->iIdxCur, 0);
    }

    /* Make cursor substitutions for cases where we want to use
    ** just the index and never reference the table.




    ** 
    ** Calls to the code generator in between sqlite3WhereBegin and
    ** sqlite3WhereEnd will have created code that references the table
    ** directly.  This loop scans all that code looking for opcodes
    ** that reference the table and converts them into opcodes that
    ** reference the index.
    */
    if( pLevel->flags & WHERE_IDX_ONLY ){
      int k, j, last;
      VdbeOp *pOp;
      Index *pIdx = pLevel->pIdx;


      assert( pIdx!=0 );
      pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
      last = sqlite3VdbeCurrentAddr(v);
      for(k=pWInfo->iTop; k<last; k++, pOp++){
        if( pOp->p1!=pLevel->iTabCur ) continue;
        if( pOp->opcode==OP_Column ){
          pOp->p1 = pLevel->iIdxCur;
          for(j=0; j<pIdx->nColumn; j++){
            if( pOp->p2==pIdx->aiColumn[j] ){
              pOp->p2 = j;

              break;
            }
          }

        }else if( pOp->opcode==OP_Rowid ){
          pOp->p1 = pLevel->iIdxCur;
          pOp->opcode = OP_IdxRowid;
        }else if( pOp->opcode==OP_NullRow ){
          pOp->opcode = OP_Noop;
        }
      }
    }
  }

  /* Final cleanup
  */
  whereInfoFree(pWInfo);
  return;
}







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** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is reponsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.265 2007/11/29 17:43:28 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
*/
#define BMS  (sizeof(Bitmask)*8)
................................................................................
    if( (pIx = pLevel->pIdx)!=0 ){
      KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
      assert( pIx->pSchema==pTab->pSchema );
      sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
      VdbeComment((v, "# %s", pIx->zName));
      sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum,
                     (char*)pKey, P3_KEYINFO_HANDOFF);




      sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1);
    }
    sqlite3CodeVerifySchema(pParse, iDb);
  }
  pWInfo->iTop = sqlite3VdbeCurrentAddr(v);

  /* Generate the code to do the search.  Each iteration of the for
................................................................................
    if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
      sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0);
    }
    if( pLevel->pIdx!=0 ){
      sqlite3VdbeAddOp(v, OP_Close, pLevel->iIdxCur, 0);
    }

    /* If this scan uses an index, make code substitutions to read data
    ** from the index in preference to the table. Sometimes, this means
    ** the table need never be read from. This is a performance boost,
    ** as the vdbe level waits until the table is read before actually
    ** seeking the table cursor to the record corresponding to the current
    ** position in the index.
    ** 
    ** Calls to the code generator in between sqlite3WhereBegin and
    ** sqlite3WhereEnd will have created code that references the table
    ** directly.  This loop scans all that code looking for opcodes
    ** that reference the table and converts them into opcodes that
    ** reference the index.
    */
    if( pLevel->pIdx ){
      int k, j, last;
      VdbeOp *pOp;
      Index *pIdx = pLevel->pIdx;
      int useIndexOnly = pLevel->flags & WHERE_IDX_ONLY;

      assert( pIdx!=0 );
      pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
      last = sqlite3VdbeCurrentAddr(v);
      for(k=pWInfo->iTop; k<last; k++, pOp++){
        if( pOp->p1!=pLevel->iTabCur ) continue;
        if( pOp->opcode==OP_Column ){

          for(j=0; j<pIdx->nColumn; j++){
            if( pOp->p2==pIdx->aiColumn[j] ){
              pOp->p2 = j;
              pOp->p1 = pLevel->iIdxCur;
              break;
            }
          }
          assert(!useIndexOnly || j<pIdx->nColumn);
        }else if( pOp->opcode==OP_Rowid ){
          pOp->p1 = pLevel->iIdxCur;
          pOp->opcode = OP_IdxRowid;
        }else if( pOp->opcode==OP_NullRow && useIndexOnly ){
          pOp->opcode = OP_Noop;
        }
      }
    }
  }

  /* Final cleanup
  */
  whereInfoFree(pWInfo);
  return;
}

Changes to test/intpkey.test.

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#
#***********************************************************************
# This file implements regression tests for SQLite library.
#
# This file implements tests for the special processing associated
# with INTEGER PRIMARY KEY columns.
#
# $Id: intpkey.test,v 1.23 2005/07/21 03:48:20 drh Exp $

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

# Create a table with a primary key and a datatype other than
# integer
#
................................................................................
    SELECT * FROM t1 WHERE c=='world';
  }
} {5 hello world 11 hello world 5}
do_test intpkey-3.8 {
  count {
    SELECT * FROM t1 WHERE c=='world' AND a>7;
  }
} {11 hello world 5}
do_test intpkey-3.9 {
  count {
    SELECT * FROM t1 WHERE 7<a;
  }
} {11 hello world 1}

# Test inequality constraints on integer primary keys and rowids







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#
#***********************************************************************
# This file implements regression tests for SQLite library.
#
# This file implements tests for the special processing associated
# with INTEGER PRIMARY KEY columns.
#
# $Id: intpkey.test,v 1.24 2007/11/29 17:43:28 danielk1977 Exp $

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

# Create a table with a primary key and a datatype other than
# integer
#
................................................................................
    SELECT * FROM t1 WHERE c=='world';
  }
} {5 hello world 11 hello world 5}
do_test intpkey-3.8 {
  count {
    SELECT * FROM t1 WHERE c=='world' AND a>7;
  }
} {11 hello world 4}
do_test intpkey-3.9 {
  count {
    SELECT * FROM t1 WHERE 7<a;
  }
} {11 hello world 1}

# Test inequality constraints on integer primary keys and rowids

Changes to test/where.test.

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# 2001 September 15
#
# 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 use of indices in WHERE clases.
#
# $Id: where.test,v 1.43 2007/06/25 16:29:34 danielk1977 Exp $

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

# Build some test data
#
do_test where-1.0 {
................................................................................
#
# do_test where-1.26 {
#   count {SELECT w FROM t1 WHERE x=3 AND y BETWEEN 121 AND 196}
# } {10 11 12 13 9}

do_test where-1.27 {
  count {SELECT w FROM t1 WHERE x=3 AND y+1==122}
} {10 17}

do_test where-1.28 {
  count {SELECT w FROM t1 WHERE x+1=4 AND y+1==122}
} {10 99}
do_test where-1.29 {
  count {SELECT w FROM t1 WHERE y==121}
} {10 99}
................................................................................
      SELECT * FROM t1 WHERE rowid IN (1,2,3,1234) order by 1;
    }
  } {1 0 4 2 1 9 3 1 16 4}
  do_test where-5.2 {
    count {
      SELECT * FROM t1 WHERE rowid+0 IN (1,2,3,1234) order by 1;
    }
  } {1 0 4 2 1 9 3 1 16 199}
  do_test where-5.3 {
    count {
      SELECT * FROM t1 WHERE w IN (-1,1,2,3) order by 1;
    }
  } {1 0 4 2 1 9 3 1 16 14}
  do_test where-5.4 {
    count {
      SELECT * FROM t1 WHERE w+0 IN (-1,1,2,3) order by 1;
    }
  } {1 0 4 2 1 9 3 1 16 199}
  do_test where-5.5 {
    count {
      SELECT * FROM t1 WHERE rowid IN 
         (select rowid from t1 where rowid IN (-1,2,4))
      ORDER BY 1;
    }
  } {2 1 9 4 2 25 3}
  do_test where-5.6 {
    count {
      SELECT * FROM t1 WHERE rowid+0 IN 
         (select rowid from t1 where rowid IN (-1,2,4))
      ORDER BY 1;
    }
  } {2 1 9 4 2 25 201}
  do_test where-5.7 {
    count {
      SELECT * FROM t1 WHERE w IN 
         (select rowid from t1 where rowid IN (-1,2,4))
      ORDER BY 1;
    }
  } {2 1 9 4 2 25 9}
  do_test where-5.8 {
    count {
      SELECT * FROM t1 WHERE w+0 IN 
         (select rowid from t1 where rowid IN (-1,2,4))
      ORDER BY 1;
    }
  } {2 1 9 4 2 25 201}
  do_test where-5.9 {
    count {
      SELECT * FROM t1 WHERE x IN (1,7) ORDER BY 1;
    }
  } {2 1 9 3 1 16 7}
  do_test where-5.10 {
    count {
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# 4 2001 September 15
#
# 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 use of indices in WHERE clases.
#
# $Id: where.test,v 1.44 2007/11/29 17:43:28 danielk1977 Exp $

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

# Build some test data
#
do_test where-1.0 {
................................................................................
#
# do_test where-1.26 {
#   count {SELECT w FROM t1 WHERE x=3 AND y BETWEEN 121 AND 196}
# } {10 11 12 13 9}

do_test where-1.27 {
  count {SELECT w FROM t1 WHERE x=3 AND y+1==122}
} {10 10}

do_test where-1.28 {
  count {SELECT w FROM t1 WHERE x+1=4 AND y+1==122}
} {10 99}
do_test where-1.29 {
  count {SELECT w FROM t1 WHERE y==121}
} {10 99}
................................................................................
      SELECT * FROM t1 WHERE rowid IN (1,2,3,1234) order by 1;
    }
  } {1 0 4 2 1 9 3 1 16 4}
  do_test where-5.2 {
    count {
      SELECT * FROM t1 WHERE rowid+0 IN (1,2,3,1234) order by 1;
    }
  } {1 0 4 2 1 9 3 1 16 102}
  do_test where-5.3 {
    count {
      SELECT * FROM t1 WHERE w IN (-1,1,2,3) order by 1;
    }
  } {1 0 4 2 1 9 3 1 16 14}
  do_test where-5.4 {
    count {
      SELECT * FROM t1 WHERE w+0 IN (-1,1,2,3) order by 1;
    }
  } {1 0 4 2 1 9 3 1 16 102}
  do_test where-5.5 {
    count {
      SELECT * FROM t1 WHERE rowid IN 
         (select rowid from t1 where rowid IN (-1,2,4))
      ORDER BY 1;
    }
  } {2 1 9 4 2 25 3}
  do_test where-5.6 {
    count {
      SELECT * FROM t1 WHERE rowid+0 IN 
         (select rowid from t1 where rowid IN (-1,2,4))
      ORDER BY 1;
    }
  } {2 1 9 4 2 25 103}
  do_test where-5.7 {
    count {
      SELECT * FROM t1 WHERE w IN 
         (select rowid from t1 where rowid IN (-1,2,4))
      ORDER BY 1;
    }
  } {2 1 9 4 2 25 9}
  do_test where-5.8 {
    count {
      SELECT * FROM t1 WHERE w+0 IN 
         (select rowid from t1 where rowid IN (-1,2,4))
      ORDER BY 1;
    }
  } {2 1 9 4 2 25 103}
  do_test where-5.9 {
    count {
      SELECT * FROM t1 WHERE x IN (1,7) ORDER BY 1;
    }
  } {2 1 9 3 1 16 7}
  do_test where-5.10 {
    count {