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 1.292 2008/03/26 14:56:35 drh Exp $
*/
#include "sqliteInt.h"

/*
** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
*/
#define BMS  (sizeof(Bitmask)*8)

  }else if( op==TK_ISNULL ){
    pTerm->prereqRight = 0;
  }else{
    pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
  }
  prereqAll = exprTableUsage(pMaskSet, pExpr);
  if( ExprHasProperty(pExpr, EP_FromJoin) ){
    Bitmask x = getMask(pMaskSet, pExpr->iRightJoinTable);
    prereqAll |= x;
    pTerm->prereqRight |= x-1; /* ON clause terms may not be used with an index
                               ** on left table of a LEFT JOIN.  Ticket #3015 */
  }
  pTerm->prereqAll = prereqAll;
  pTerm->leftCursor = -1;
  pTerm->iParent = -1;
  pTerm->eOperator = 0;
  if( allowedOp(op) && (pTerm->prereqRight & prereqLeft)==0 ){
    Expr *pLeft = pExpr->pLeft;

  /* Special case: a WHERE clause that is constant.  Evaluate the
  ** expression and either jump over all of the code or fall thru.
  */
  if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstantNotJoin(pWhere)) ){
    sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, SQLITE_JUMPIFNULL);
    pWhere = 0;
  }

  /* Assign a bit from the bitmask to every term in the FROM clause.
  **
  ** When assigning bitmask values to FROM clause cursors, it must be
  ** the case that if X is the bitmask for the N-th FROM clause term then
  ** the bitmask for all FROM clause terms to the left of the N-th term
  ** is (X-1).   An expression from the ON clause of a LEFT JOIN can use
  ** its Expr.iRightJoinTable value to find the bitmask of the right table
  ** of the join.  Subtracting one from the right table bitmask gives a
  ** bitmask for all tables to the left of the join.  Knowing the bitmask
  ** for all tables to the left of a left join is important.  Ticket #3015.
  */
  for(i=0; i<pTabList->nSrc; i++){
    createMask(&maskSet, pTabList->a[i].iCursor);
  }
#ifndef NDEBUG
  {
    Bitmask toTheLeft = 0;
    for(i=0; i<pTabList->nSrc; i++){
      Bitmask m = getMask(&maskSet, pTabList->a[i].iCursor);
      assert( (m-1)==toTheLeft );
      toTheLeft |= m;
    }
  }
#endif

  /* Analyze all of the subexpressions.  Note that exprAnalyze() might
  ** add new virtual terms onto the end of the WHERE clause.  We do not
  ** want to analyze these virtual terms, so start analyzing at the end
  ** and work forward so that the added virtual terms are never processed.
  */



  exprAnalyzeAll(pTabList, &wc);
  if( db->mallocFailed ){
    goto whereBeginNoMem;
  }

  /* Chose the best index to use for each table in the FROM clause.
  **

# 2007 June 8
#
# 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 that terms in the ON clause of
# a LEFT OUTER JOIN are not used with indices.  See ticket #3015.
#
# $Id: where6.test,v 1.1 2008/03/26 14:56:35 drh Exp $

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

# Build some test data
#
do_test where6-1.0 {
  execsql {
    CREATE TABLE t1(a INTEGER PRIMARY KEY,b,c);
    INSERT INTO t1 VALUES(1,3,1);
    INSERT INTO t1 VALUES(2,4,2);
    CREATE TABLE t2(x INTEGER PRIMARY KEY);
    INSERT INTO t2 VALUES(3);

    SELECT * FROM t1 LEFT JOIN t2 ON b=x AND c=1;
  }
} {1 3 1 3 2 4 2 {}}
do_test where6-1.1 {
  execsql {
    SELECT * FROM t1 LEFT JOIN t2 ON b=x WHERE c=1;
  }
} {1 3 1 3}
do_test where6-1.2 {
  execsql {
    CREATE INDEX i1 ON t1(c);

    SELECT * FROM t1 LEFT JOIN t2 ON b=x AND c=1;
  }
} {1 3 1 3 2 4 2 {}}
do_test where6-1.3 {
  execsql {
    SELECT * FROM t1 LEFT JOIN t2 ON b=x WHERE c=1;
  }
} {1 3 1 3}

finish_test