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 1.236 2007/01/25 16:56:07 drh Exp $
*/
#include "sqliteInt.h"

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

#define WO_LE     (WO_EQ<<(TK_LE-TK_EQ))
#define WO_GT     (WO_EQ<<(TK_GT-TK_EQ))
#define WO_GE     (WO_EQ<<(TK_GE-TK_EQ))
#define WO_MATCH  64
#define WO_ISNULL 128

/*
** Value for flags returned by bestIndex().  
**
** The least significant byte is reserved as a mask for WO_ values above.
** The WhereLevel.flags field is usually set to WO_IN|WO_EQ|WO_ISNULL.
** But if the table is the right table of a left join, WhereLevel.flags
** is set to WO_IN|WO_EQ.  The WhereLevel.flags field can then be used as
** the "op" parameter to findTerm when we are resolving equality constraints.
** ISNULL constraints will then not be used on the right table of a left
** join.  Tickets #2177 and #2189.
*/
#define WHERE_ROWID_EQ     0x000100   /* rowid=EXPR or rowid IN (...) */
#define WHERE_ROWID_RANGE  0x000200   /* rowid<EXPR and/or rowid>EXPR */
#define WHERE_COLUMN_EQ    0x001000   /* x=EXPR or x IN (...) */
#define WHERE_COLUMN_RANGE 0x002000   /* x<EXPR and/or x>EXPR */
#define WHERE_COLUMN_IN    0x004000   /* x IN (...) */
#define WHERE_TOP_LIMIT    0x010000   /* x<EXPR or x<=EXPR constraint */
#define WHERE_BTM_LIMIT    0x020000   /* x>EXPR or x>=EXPR constraint */
#define WHERE_IDX_ONLY     0x080000   /* Use index only - omit table */
#define WHERE_ORDERBY      0x100000   /* Output will appear in correct order */
#define WHERE_REVERSE      0x200000   /* Scan in reverse order */
#define WHERE_UNIQUE       0x400000   /* Selects no more than one row */
#define WHERE_VIRTUALTABLE 0x800000   /* Use virtual-table processing */

/*
** Initialize a preallocated WhereClause structure.
*/
static void whereClauseInit(WhereClause *pWC, Parse *pParse){
  pWC->pParse = pParse;
  pWC->nTerm = 0;

  }

  /* Report the best result
  */
  *ppIndex = bestIdx;
  TRACE(("best index is %s, cost=%.9g, flags=%x, nEq=%d\n",
        bestIdx ? bestIdx->zName : "(none)", lowestCost, bestFlags, bestNEq));
  *pFlags = bestFlags | eqTermMask;
  *pnEq = bestNEq;
  return lowestCost;
}


/*
** Disable a term in the WHERE clause.  Except, do not disable the term

  }

  /* Evaluate the equality constraints
  */
  assert( pIdx->nColumn>=nEq );
  for(j=0; j<nEq; j++){
    int k = pIdx->aiColumn[j];
    pTerm = findTerm(pWC, iCur, k, notReady, pLevel->flags, pIdx);
    if( pTerm==0 ) break;
    assert( (pTerm->flags & TERM_CODED)==0 );
    codeEqualityTerm(pParse, pTerm, brk, pLevel);
    if( (pTerm->eOperator & WO_ISNULL)==0 ){
      sqlite3VdbeAddOp(v, OP_IsNull, termsInMem ? -1 : -(j+1), brk);
    }
    if( termsInMem ){

# This file implements regression tests for SQLite library.  The
# focus of this file is testing the use of indices in WHERE clauses.
# This file was created when support for optimizing IS NULL phrases
# was added.  And so the principle purpose of this file is to test
# that IS NULL phrases are correctly optimized.  But you can never
# have too many tests, so some other tests are thrown in as well.
#
# $Id: where4.test,v 1.2 2007/01/25 16:56:08 drh Exp $

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

# Build some test data
#
do_test where4-1.0 {

  }
} {2 2 {} 3 {} {}}
do_test where4-3.2 {
  execsql {
    SELECT * FROM t2 LEFT JOIN t3 ON a=x WHERE y IS NULL;
  }
} {2 2 {} 3 {} {}}

# Ticket #2189.  Probably the same bug as #2177.
#
do_test where4-4.1 {
  execsql {
    CREATE TABLE test(col1 TEXT PRIMARY KEY);
    INSERT INTO test(col1) values('a');
    INSERT INTO test(col1) values('b');
    INSERT INTO test(col1) values('c');
    CREATE TABLE test2(col1 TEXT PRIMARY KEY);
    INSERT INTO test2(col1) values('a');
    INSERT INTO test2(col1) values('b');
    INSERT INTO test2(col1) values('c');
    SELECT * FROM test t1 LEFT OUTER JOIN test2 t2 ON t1.col1 = t2.col1
      WHERE +t2.col1 IS NULL;
  }
} {}
do_test where4-4.2 {
  execsql {
    SELECT * FROM test t1 LEFT OUTER JOIN test2 t2 ON t1.col1 = t2.col1
      WHERE t2.col1 IS NULL;
  }
} {}
do_test where4-4.3 {
  execsql {
    SELECT * FROM test t1 LEFT OUTER JOIN test2 t2 ON t1.col1 = t2.col1
      WHERE +t1.col1 IS NULL;
  }
} {}
do_test where4-4.4 {
  execsql {
    SELECT * FROM test t1 LEFT OUTER JOIN test2 t2 ON t1.col1 = t2.col1
      WHERE t1.col1 IS NULL;
  }
} {}
    

integrity_check {where4-99.0}

finish_test