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Make sure that the optimizer realizes that an "x IS NULL" contraint does not

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necessarily give a single-row result even on a UNIQUE index.  Ticket #3824. (CVS 6545)

FossilOrigin-Name: 207335fdbf992a2f5bc5982b3163a38016ba1b21
This commit is contained in:
drh
2009-04-24 14:51:42 +00:00
parent 4598b8e4a1
commit 46619d6787
4 changed files with 117 additions and 20 deletions
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32
src/where.c
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@@ -16,7 +16,7 @@
** 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 1.388 2009/04/23 13:22:44 drh Exp $
** $Id: where.c,v 1.389 2009/04/24 14:51:42 drh Exp $
*/
#include "sqliteInt.h"
@@ -226,11 +226,12 @@ struct WhereCost {
*/
#define WHERE_ROWID_EQ 0x00001000 /* rowid=EXPR or rowid IN (...) */
#define WHERE_ROWID_RANGE 0x00002000 /* rowid<EXPR and/or rowid>EXPR */
#define WHERE_COLUMN_EQ 0x00010000 /* x=EXPR or x IN (...) */
#define WHERE_COLUMN_EQ 0x00010000 /* x=EXPR or x IN (...) or x IS NULL */
#define WHERE_COLUMN_RANGE 0x00020000 /* x<EXPR and/or x>EXPR */
#define WHERE_COLUMN_IN 0x00040000 /* x IN (...) */
#define WHERE_INDEXED 0x00070000 /* Anything that uses an index */
#define WHERE_IN_ABLE 0x00071000 /* Able to support an IN operator */
#define WHERE_COLUMN_NULL 0x00080000 /* x IS NULL */
#define WHERE_INDEXED 0x000f0000 /* Anything that uses an index */
#define WHERE_IN_ABLE 0x000f1000 /* Able to support an IN operator */
#define WHERE_TOP_LIMIT 0x00100000 /* x<EXPR or x<=EXPR constraint */
#define WHERE_BTM_LIMIT 0x00200000 /* x>EXPR or x>=EXPR constraint */
#define WHERE_IDX_ONLY 0x00800000 /* Use index only - omit table */
@@ -2030,9 +2031,10 @@ static void bestBtreeIndex(
WHERETRACE(("... index %s:\n", pProbe->zName));
/* Count the number of columns in the index that are satisfied
** by x=EXPR constraints or x IN (...) constraints. For a term
** of the form x=EXPR we only have to do a single binary search.
** But for x IN (...) we have to do a number of binary searched
** by x=EXPR or x IS NULL constraints or x IN (...) constraints.
** For a term of the form x=EXPR or x IS NULL we only have to do
** a single binary search. But for x IN (...) we have to do a
** number of binary searched
** equal to the number of entries on the RHS of the IN operator.
** The inMultipler variable with try to estimate the number of
** binary searches needed.
@@ -2052,6 +2054,8 @@ static void bestBtreeIndex(
}else if( pExpr->x.pList ){
inMultiplier *= pExpr->x.pList->nExpr + 1;
}
}else if( pTerm->eOperator & WO_ISNULL ){
wsFlags |= WHERE_COLUMN_NULL;
}
}
nRow = pProbe->aiRowEst[i] * inMultiplier;
@@ -2064,9 +2068,12 @@ static void bestBtreeIndex(
}
cost = nRow + inMultiplier*estLog(pProbe->aiRowEst[0]);
nEq = i;
if( pProbe->onError!=OE_None && (wsFlags & WHERE_COLUMN_IN)==0
&& nEq==pProbe->nColumn ){
wsFlags |= WHERE_UNIQUE;
if( pProbe->onError!=OE_None && nEq==pProbe->nColumn ){
testcase( wsFlags & WHERE_COLUMN_IN );
testcase( wsFlags & WHERE_COLUMN_NULL );
if( (wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_NULL))==0 ){
wsFlags |= WHERE_UNIQUE;
}
}
WHERETRACE(("...... nEq=%d inMult=%.9g nRow=%.9g cost=%.9g\n",
nEq, inMultiplier, nRow, cost));
@@ -2097,8 +2104,9 @@ static void bestBtreeIndex(
/* Add the additional cost of sorting if that is a factor.
*/
if( pOrderBy ){
if( (wsFlags & WHERE_COLUMN_IN)==0 &&
isSortingIndex(pParse,pWC->pMaskSet,pProbe,iCur,pOrderBy,nEq,&rev) ){
if( (wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_NULL))==0
&& isSortingIndex(pParse,pWC->pMaskSet,pProbe,iCur,pOrderBy,nEq,&rev)
){
if( wsFlags==0 ){
wsFlags = WHERE_COLUMN_RANGE;
}