SQLite

** 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 1.128 2005/01/11 18:13:56 drh Exp $
*/
#include "sqliteInt.h"

/*
** The query generator uses an array of instances of this structure to
** help it analyze the subexpressions of the WHERE clause.  Each WHERE
** clause subexpression is separated from the others by an AND operator.

      for(j=0; j<nColumn; j++){
        for(pTerm=aExpr, k=0; k<nExpr; k++, pTerm++){
          Expr *pX = pTerm->p;
          if( pX==0 ) continue;
          if( pTerm->idxLeft==iCur
             && (pTerm->prereqRight & loopMask)==pTerm->prereqRight 
             && pX->pLeft->iColumn==pIdx->aiColumn[j]
             && (pX->op==TK_EQ || pX->op==TK_IN)
          ){
            char idxaff = pIdx->pTable->aCol[pX->pLeft->iColumn].affinity;
            if( sqlite3IndexAffinityOk(pX, idxaff) ){
              codeEqualityTerm(pParse, pTerm, brk, pLevel);
              break;
            }
          }

# 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 1.27 2005/01/11 18:13:57 drh Exp $

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

# Build some test data
#
do_test where-1.0 {

} {98 99 100 3}
do_test where-1.31 {
  count {SELECT w FROM t1 WHERE w>=97}
} {97 98 99 100 4}
do_test where-1.33 {
  count {SELECT w FROM t1 WHERE w==97}
} {97 2}
do_test where-1.33.1  {
  count {SELECT w FROM t1 WHERE w<=97 AND w==97}
} {97 2}
do_test where-1.33.2  {
  count {SELECT w FROM t1 WHERE w<98 AND w==97}
} {97 2}
do_test where-1.33.3  {
  count {SELECT w FROM t1 WHERE w>=97 AND w==97}
} {97 2}
do_test where-1.33.4  {
  count {SELECT w FROM t1 WHERE w>96 AND w==97}
} {97 2}
do_test where-1.33.5  {
  count {SELECT w FROM t1 WHERE w==97 AND w==97}
} {97 2}
do_test where-1.34 {
  count {SELECT w FROM t1 WHERE w+1==98}
} {97 99}
do_test where-1.35 {
  count {SELECT w FROM t1 WHERE w<3}
} {1 2 2}
do_test where-1.36 {

    SELECT * FROM t3 WHERE a IN (3,5,7,1,9,4,2) ORDER BY a LIMIT 3
  }
} {1 100 4 2 99 9 3 98 16 sort}
do_test where-6.9.1 {
  cksort {
    SELECT * FROM t3 WHERE a=1 AND c>0 ORDER BY a LIMIT 3
  }
} {1 100 4 nosort}
do_test where-6.9.1.1 {
  cksort {
    SELECT * FROM t3 WHERE a>=1 AND a=1 AND c>0 ORDER BY a LIMIT 3
  }
} {1 100 4 nosort}
do_test where-6.9.1.2 {
  cksort {
    SELECT * FROM t3 WHERE a<2 AND a=1 AND c>0 ORDER BY a LIMIT 3
  }
} {1 100 4 nosort}
do_test where-6.9.2 {
  cksort {
    SELECT * FROM t3 WHERE a=1 AND c>0 ORDER BY a,c LIMIT 3
  }
} {1 100 4 nosort}
do_test where-6.9.3 {