SQLite

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.297 2007/06/08 00:20:48 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Return the 'affinity' of the expression pExpr if any.
**

** then do nothing.
**
** After walking the whole tree, if no nodes are found that disqualify
** the expression as constant, then we assume the whole expression
** is constant.  See sqlite3ExprIsConstant() for additional information.
*/
static int exprNodeIsConstant(void *pArg, Expr *pExpr){
  int *pN = (int*)pArg;

  /* If *pArg is 3 then any term of the expression that comes from
  ** the ON or USING clauses of a join disqualifies the expression
  ** from being considered constant. */
  if( (*pN)==3 && ExprHasAnyProperty(pExpr, EP_FromJoin) ){
    *pN = 0;
    return 2;
  }

  switch( pExpr->op ){
    /* Consider functions to be constant if all their arguments are constant
    ** and *pArg==2 */
    case TK_FUNCTION:
      if( (*pN)==2 ) return 0;
      /* Fall through */
    case TK_ID:
    case TK_COLUMN:
    case TK_DOT:
    case TK_AGG_FUNCTION:
    case TK_AGG_COLUMN:
#ifndef SQLITE_OMIT_SUBQUERY
    case TK_SELECT:
    case TK_EXISTS:
#endif
      *pN = 0;
      return 2;
    case TK_IN:
      if( pExpr->pSelect ){
        *pN = 0;
        return 2;
      }
    default:
      return 0;
  }
}

/*
** Walk an expression tree.  Return 1 if the expression is constant
** and 0 if it involves variables or function calls.
**
** For the purposes of this function, a double-quoted string (ex: "abc")
** is considered a variable but a single-quoted string (ex: 'abc') is
** a constant.
*/
int sqlite3ExprIsConstant(Expr *p){
  int isConst = 1;
  walkExprTree(p, exprNodeIsConstant, &isConst);
  return isConst;
}

/*
** Walk an expression tree.  Return 1 if the expression is constant
** that does no originate from the ON or USING clauses of a join.
** Return 0 if it involves variables or function calls or terms from
** an ON or USING clause.
*/
int sqlite3ExprIsConstantNotJoin(Expr *p){
  int isConst = 3;
  walkExprTree(p, exprNodeIsConstant, &isConst);
  return isConst!=0;
}

/*
** Walk an expression tree.  Return 1 if the expression is constant
** or a function call with constant arguments.  Return and 0 if there
** are any variables.
**
** For the purposes of this function, a double-quoted string (ex: "abc")

/*
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.571 2007/06/08 00:20:48 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_
#include "limits.h"


#if defined(SQLITE_TCL) || defined(TCLSH)

void sqlite3Randomness(int, void*);
void sqlite3RollbackAll(sqlite3*);
void sqlite3CodeVerifySchema(Parse*, int);
void sqlite3BeginTransaction(Parse*, int);
void sqlite3CommitTransaction(Parse*);
void sqlite3RollbackTransaction(Parse*);
int sqlite3ExprIsConstant(Expr*);
int sqlite3ExprIsConstantNotJoin(Expr*);
int sqlite3ExprIsConstantOrFunction(Expr*);
int sqlite3ExprIsInteger(Expr*, int*);
int sqlite3IsRowid(const char*);
void sqlite3GenerateRowDelete(sqlite3*, Vdbe*, Table*, int, int);
void sqlite3GenerateRowIndexDelete(Vdbe*, Table*, int, char*);
void sqlite3GenerateIndexKey(Vdbe*, Index*, int);
void sqlite3GenerateConstraintChecks(Parse*,Table*,int,char*,int,int,int,int);

** 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 1.251 2007/06/08 00:20:48 drh Exp $
*/
#include "sqliteInt.h"

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

  pWInfo->pParse = pParse;
  pWInfo->pTabList = pTabList;
  pWInfo->iBreak = sqlite3VdbeMakeLabel(v);

  /* 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, 1);
    pWhere = 0;
  }

  /* 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

#
#***********************************************************************
# This file implements regression tests for SQLite library.
#
# This file implements tests for left outer joins containing ON
# clauses that restrict the scope of the left term of the join.
#
# $Id: join5.test,v 1.2 2007/06/08 00:20:48 drh Exp $

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


do_test join5-1.1 {
  execsql {

} {1 5 0 {} {} {} {} 2 11 2 {} {} 11 t3-11 3 12 1 12 t2-12 {} {}}
do_test join5-1.5 {
  execsql {
    select * from t1 left join t2 on t1.b=t2.x and t1.c=1
                     left join t3 on t1.b=t3.p where t1.c=2
  }
} {2 11 2 {} {} 11 t3-11}

# Ticket #2403
#
do_test join5-2.1 {
  execsql {
    CREATE TABLE ab(a,b);
    INSERT INTO "ab" VALUES(1,2);
    INSERT INTO "ab" VALUES(3,NULL);

    CREATE TABLE xy(x,y);
    INSERT INTO "xy" VALUES(2,3);
    INSERT INTO "xy" VALUES(NULL,1);
  }
  execsql {SELECT * FROM xy LEFT JOIN ab ON 0}
} {2 3 {} {} {} 1 {} {}}
do_test join5-2.2 {
  execsql {SELECT * FROM xy LEFT JOIN ab ON 1}
} {2 3 1 2 2 3 3 {} {} 1 1 2 {} 1 3 {}}
do_test join5-2.3 {
  execsql {SELECT * FROM xy LEFT JOIN ab ON NULL}
} {2 3 {} {} {} 1 {} {}}
do_test join5-2.4 {
  execsql {SELECT * FROM xy LEFT JOIN ab ON 0 WHERE 0}
} {}
do_test join5-2.5 {
  execsql {SELECT * FROM xy LEFT JOIN ab ON 1 WHERE 0}
} {}
do_test join5-2.6 {
  execsql {SELECT * FROM xy LEFT JOIN ab ON NULL WHERE 0}
} {}
do_test join5-2.7 {
  execsql {SELECT * FROM xy LEFT JOIN ab ON 0 WHERE 1}
} {2 3 {} {} {} 1 {} {}}
do_test join5-2.8 {
  execsql {SELECT * FROM xy LEFT JOIN ab ON 1 WHERE 1}
} {2 3 1 2 2 3 3 {} {} 1 1 2 {} 1 3 {}}
do_test join5-2.9 {
  execsql {SELECT * FROM xy LEFT JOIN ab ON NULL WHERE 1}
} {2 3 {} {} {} 1 {} {}}
do_test join5-2.10 {
  execsql {SELECT * FROM xy LEFT JOIN ab ON 0 WHERE NULL}
} {}
do_test join5-2.11 {
  execsql {SELECT * FROM xy LEFT JOIN ab ON 1 WHERE NULL}
} {}
do_test join5-2.12 {
  execsql {SELECT * FROM xy LEFT JOIN ab ON NULL WHERE NULL}
} {}


finish_test