SQLite

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is responsible 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 1.397 2009/05/22 15:43:27 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** Trace output macros
*/
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)

/*
** An instance of the following structure holds all information about a
** WHERE clause.  Mostly this is a container for one or more WhereTerms.
*/
struct WhereClause {
  Parse *pParse;           /* The parser context */
  WhereMaskSet *pMaskSet;  /* Mapping of table cursor numbers to bitmasks */
  Bitmask vmask;           /* Bitmask identifying virtual table cursors */
  u8 op;                   /* Split operator.  TK_AND or TK_OR */
  int nTerm;               /* Number of terms */
  int nSlot;               /* Number of entries in a[] */
  WhereTerm *a;            /* Each a[] describes a term of the WHERE cluase */
  WhereTerm aStatic[4];    /* Initial static space for a[] */
};

  WhereMaskSet *pMaskSet   /* Mapping from table cursor numbers to bitmasks */
){
  pWC->pParse = pParse;
  pWC->pMaskSet = pMaskSet;
  pWC->nTerm = 0;
  pWC->nSlot = ArraySize(pWC->aStatic);
  pWC->a = pWC->aStatic;
  pWC->vmask = 0;
}

/* Forward reference */
static void whereClauseClear(WhereClause*);

/*
** Deallocate all memory associated with a WhereOrInfo object.

  exprAnalyzeAll(pSrc, pOrWc);
  if( db->mallocFailed ) return;
  assert( pOrWc->nTerm>=2 );

  /*
  ** Compute the set of tables that might satisfy cases 1 or 2.
  */
  indexable = ~(Bitmask)0;
  chngToIN = ~(pWC->vmask);
  for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0 && indexable; i--, pOrTerm++){
    if( (pOrTerm->eOperator & WO_SINGLE)==0 ){
      WhereAndInfo *pAndInfo;
      assert( pOrTerm->eOperator==0 );
      assert( (pOrTerm->wtFlags & (TERM_ANDINFO|TERM_ORINFO))==0 );
      chngToIN = 0;
      pAndInfo = sqlite3DbMallocRaw(db, sizeof(*pAndInfo));

  ** 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.
  **
  ** Configure the WhereClause.vmask variable so that bits that correspond
  ** to virtual table cursors are set. This is used to selectively disable 
  ** the OR-to-IN transformation in exprAnalyzeOrTerm(). It is not helpful 
  ** with virtual tables.
  */
  assert( pWC->vmask==0 && pMaskSet->n==0 );
  for(i=0; i<pTabList->nSrc; i++){
    createMask(pMaskSet, pTabList->a[i].iCursor);
    if( pTabList->a[i].pTab && IsVirtual(pTabList->a[i].pTab) ){
      pWC->vmask |= ((Bitmask)1 << i);
    }
  }
#ifndef NDEBUG
  {
    Bitmask toTheLeft = 0;
    for(i=0; i<pTabList->nSrc; i++){
      Bitmask m = getMask(pMaskSet, pTabList->a[i].iCursor);
      assert( (m-1)==toTheLeft );

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

ifcapable !vtab {
  finish_test
  return
}

register_echo_module [sqlite3_connection_pointer db]

do_test tkt3871-1.1 {
  execsql {
    BEGIN;
    CREATE TABLE t1(a PRIMARY KEY, b UNIQUE);
  }
  for {set i 0} {$i < 500} {incr i} {
    execsql { INSERT INTO t1 VALUES($i, $i*$i) }
  }
  execsql COMMIT
  execsql { 
    CREATE VIRTUAL TABLE e USING echo(t1);
    SELECT count(*) FROM e;
  }
} {500}

do_test tkt3871-1.2 {
  execsql { SELECT * FROM e WHERE a = 1 OR a = 2 }
} {1 1 2 4}
do_test tkt3871-1.3 {
  set echo_module ""
  execsql { SELECT * FROM e WHERE a = 1 OR a = 2 }
  set echo_module
} [list \
  xFilter {SELECT rowid, * FROM 't1' WHERE a = ?} 1 \
  xFilter {SELECT rowid, * FROM 't1' WHERE a = ?} 2 \
]

do_test tkt3871-1.4 {
  execsql { SELECT * FROM e WHERE a = 1 OR a = 2 OR b = 9 }
} {1 1 2 4 3 9}
do_test tkt3871-1.5 {
  set echo_module ""
  execsql { SELECT * FROM e WHERE a = 1 OR a = 2 OR b = 9 }
  set echo_module
} [list \
  xFilter {SELECT rowid, * FROM 't1' WHERE a = ?} 1 \
  xFilter {SELECT rowid, * FROM 't1' WHERE a = ?} 2 \
  xFilter {SELECT rowid, * FROM 't1' WHERE b = ?} 9
]


finish_test