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ON-clause terms in a LEFT JOIN that restrict only the left table, should not

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really restrict the left table but instead rows that fail to meet the condition
to be joined with NULL rows from the right table. (CVS 2725)

FossilOrigin-Name: ea10f9785e3c5248dafcc297f3a2c5465b6e0dba
This commit is contained in:
drh
2005-09-19 21:05:48 +00:00
parent eb8cbaeb18
commit 22d6a53a77
6 changed files with 108 additions and 19 deletions
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34
src/select.c
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@@ -12,7 +12,7 @@
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.271 2005/09/19 17:35:53 drh Exp $
** $Id: select.c,v 1.272 2005/09/19 21:05:49 drh Exp $
*/
#include "sqliteInt.h"
@@ -179,6 +179,7 @@ static void addWhereTerm(
const char *zAlias1, /* Alias for first table. May be NULL */
const Table *pTab2, /* Second table */
const char *zAlias2, /* Alias for second table. May be NULL */
int iRightJoinTable, /* VDBE cursor for the right table */
Expr **ppExpr /* Add the equality term to this expression */
){
Expr *pE1a, *pE1b, *pE1c;
@@ -199,11 +200,14 @@ static void addWhereTerm(
pE2c = sqlite3Expr(TK_DOT, pE2b, pE2a, 0);
pE = sqlite3Expr(TK_EQ, pE1c, pE2c, 0);
ExprSetProperty(pE, EP_FromJoin);
pE->iRightJoinTable = iRightJoinTable;
*ppExpr = sqlite3ExprAnd(*ppExpr, pE);
}
/*
** Set the EP_FromJoin property on all terms of the given expression.
** And set the Expr.iRightJoinTable to iTable for every term in the
** expression.
**
** The EP_FromJoin property is used on terms of an expression to tell
** the LEFT OUTER JOIN processing logic that this term is part of the
@@ -211,11 +215,26 @@ static void addWhereTerm(
** of the more general WHERE clause. These terms are moved over to the
** WHERE clause during join processing but we need to remember that they
** originated in the ON or USING clause.
**
** The Expr.iRightJoinTable tells the WHERE clause processing that the
** expression depends on table iRightJoinTable even if that table is not
** explicitly mentioned in the expression. That information is needed
** for cases like this:
**
** SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.b AND t1.x=5
**
** The where clause needs to defer the handling of the t1.x=5
** term until after the t2 loop of the join. In that way, a
** NULL t2 row will be inserted whenever t1.x!=5. If we do not
** defer the handling of t1.x=5, it will be processed immediately
** after the t1 loop and rows with t1.x!=5 will never appear in
** the output, which is incorrect.
*/
static void setJoinExpr(Expr *p){
static void setJoinExpr(Expr *p, int iTable){
while( p ){
ExprSetProperty(p, EP_FromJoin);
setJoinExpr(p->pLeft);
p->iRightJoinTable = iTable;
setJoinExpr(p->pLeft, iTable);
p = p->pRight;
}
}
@@ -262,7 +281,9 @@ static int sqliteProcessJoin(Parse *pParse, Select *p){
char *zName = pLeftTab->aCol[j].zName;
if( columnIndex(pRightTab, zName)>=0 ){
addWhereTerm(zName, pLeftTab, pLeft->zAlias,
pRightTab, pRight->zAlias, &p->pWhere);
pRightTab, pRight->zAlias,
pRight->iCursor, &p->pWhere);
}
}
}
@@ -279,7 +300,7 @@ static int sqliteProcessJoin(Parse *pParse, Select *p){
** an AND operator.
*/
if( pLeft->pOn ){
setJoinExpr(pLeft->pOn);
setJoinExpr(pLeft->pOn, pRight->iCursor);
p->pWhere = sqlite3ExprAnd(p->pWhere, pLeft->pOn);
pLeft->pOn = 0;
}
@@ -301,7 +322,8 @@ static int sqliteProcessJoin(Parse *pParse, Select *p){
return 1;
}
addWhereTerm(zName, pLeftTab, pLeft->zAlias,
pRightTab, pRight->zAlias, &p->pWhere);
pRightTab, pRight->zAlias,
pRight->iCursor, &p->pWhere);
}
}
}