database/sqlite
1
0
Fork 0
mirror of https://github.com/sqlite/sqlite.git synced 2025-11-08 03:22:21 +03:00
Code Activity

Avoid reevaluating WHERE and ORDER BY expressions that alias terms in the

Browse Source 
result set.  Ticket #3343.  Note that aliased GROUP BY expressions are still
evaluated twice. (CVS 5637)

FossilOrigin-Name: ab0292caa5887cc1bdc0e8c9d3f3502b83975440
This commit is contained in:
drh
2008-08-29 02:14:02 +00:00
parent 3fb120cb9d
commit 8b213899e8
8 changed files with 285 additions and 51 deletions
Download Patch File Download Diff File Expand all files Collapse all files

68
src/expr.c
View File

@@ -12,7 +12,7 @@
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.391 2008/08/22 17:34:45 drh Exp $
** $Id: expr.c,v 1.392 2008/08/29 02:14:03 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
@@ -701,6 +701,7 @@ ExprList *sqlite3ExprListDup(sqlite3 *db, ExprList *p){
pItem->sortOrder = pOldItem->sortOrder;
pItem->done = 0;
pItem->iCol = pOldItem->iCol;
pItem->iAlias = pOldItem->iAlias;
}
return pNew;
}
@@ -829,6 +830,7 @@ ExprList *sqlite3ExprListAppend(
memset(pItem, 0, sizeof(*pItem));
pItem->zName = sqlite3NameFromToken(db, pName);
pItem->pExpr = pExpr;
pItem->iAlias = 0;
}
return pList;
@@ -1664,12 +1666,47 @@ void sqlite3ExprHardCopy(Parse *pParse, int iReg, int nReg){
}
}
/*
** Generate code to store the value of the iAlias-th alias in register
** target. The first time this is called, pExpr is evaluated to compute
** the value of the alias. The value is stored in an auxiliary register
** and the number of that register is returned. On subsequent calls,
** the register number is returned without generating any code.
**
** Note that in order for this to work, code must be generated in the
** same order that it is executed.
**
** Aliases are numbered starting with 1. So iAlias is in the range
** of 1 to pParse->nAlias inclusive.
**
** pParse->aAlias[iAlias-1] records the register number where the value
** of the iAlias-th alias is stored. If zero, that means that the
** alias has not yet been computed.
*/
static int codeAlias(Parse *pParse, int iAlias, Expr *pExpr){
sqlite3 *db = pParse->db;
int iReg;
if( pParse->aAlias==0 ){
pParse->aAlias = sqlite3DbMallocZero(db,
sizeof(pParse->aAlias[0])*pParse->nAlias );
if( db->mallocFailed ) return 0;
}
assert( iAlias>0 && iAlias<=pParse->nAlias );
iReg = pParse->aAlias[iAlias-1];
if( iReg==0 ){
iReg = ++pParse->nMem;
sqlite3ExprCode(pParse, pExpr, iReg);
pParse->aAlias[iAlias-1] = iReg;
}
return iReg;
}
/*
** Generate code into the current Vdbe to evaluate the given
** expression. Attempt to store the results in register "target".
** Return the register where results are stored.
**
** With this routine, there is no guaranteed that results will
** With this routine, there is no guarantee that results will
** be stored in target. The result might be stored in some other
** register if it is convenient to do so. The calling function
** must check the return code and move the results to the desired
@@ -1682,8 +1719,10 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
int regFree1 = 0; /* If non-zero free this temporary register */
int regFree2 = 0; /* If non-zero free this temporary register */
int r1, r2, r3, r4; /* Various register numbers */
sqlite3 *db;
assert( v!=0 || pParse->db->mallocFailed );
db = pParse->db;
assert( v!=0 || db->mallocFailed );
assert( target>0 && target<=pParse->nMem );
if( v==0 ) return 0;
@@ -1729,7 +1768,7 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
break;
}
case TK_STRING: {
sqlite3DequoteExpr(pParse->db, pExpr);
sqlite3DequoteExpr(db, pExpr);
sqlite3VdbeAddOp4(v,OP_String8, 0, target, 0,
(char*)pExpr->token.z, pExpr->token.n);
break;
@@ -1765,6 +1804,10 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
inReg = pExpr->iTable;
break;
}
case TK_AS: {
inReg = codeAlias(pParse, pExpr->iTable, pExpr->pLeft);
break;
}
#ifndef SQLITE_OMIT_CAST
case TK_CAST: {
/* Expressions of the form: CAST(pLeft AS token) */
@@ -1921,7 +1964,6 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
const char *zId;
int constMask = 0;
int i;
sqlite3 *db = pParse->db;
u8 enc = ENC(db);
CollSeq *pColl = 0;
@@ -1929,7 +1971,7 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
testcase( op==TK_FUNCTION );
zId = (char*)pExpr->token.z;
nId = pExpr->token.n;
pDef = sqlite3FindFunction(pParse->db, zId, nId, nExpr, enc, 0);
pDef = sqlite3FindFunction(db, zId, nId, nExpr, enc, 0);
assert( pDef!=0 );
if( pList ){
nExpr = pList->nExpr;
@@ -1966,7 +2008,7 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
}
}
if( pDef->needCollSeq ){
if( !pColl ) pColl = pParse->db->pDfltColl;
if( !pColl ) pColl = db->pDfltColl;
sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
}
sqlite3VdbeAddOp4(v, OP_Function, constMask, r1, target,
@@ -2206,7 +2248,7 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
assert( pExpr->iColumn==OE_Rollback ||
pExpr->iColumn == OE_Abort ||
pExpr->iColumn == OE_Fail );
sqlite3DequoteExpr(pParse->db, pExpr);
sqlite3DequoteExpr(db, pExpr);
sqlite3VdbeAddOp4(v, OP_Halt, SQLITE_CONSTRAINT, pExpr->iColumn, 0,
(char*)pExpr->token.z, pExpr->token.n);
} else {
@@ -2422,7 +2464,13 @@ int sqlite3ExprCodeExprList(
assert( target>0 );
n = pList->nExpr;
for(pItem=pList->a, i=0; i<n; i++, pItem++){
sqlite3ExprCode(pParse, pItem->pExpr, target+i);
if( pItem->iAlias ){
int iReg = codeAlias(pParse, pItem->iAlias, pItem->pExpr);
Vdbe *v = sqlite3GetVdbe(pParse);
sqlite3VdbeAddOp2(v, OP_SCopy, iReg, target+i);
}else{
sqlite3ExprCode(pParse, pItem->pExpr, target+i);
}
if( doHardCopy ) sqlite3ExprHardCopy(pParse, target, n);
}
return n;
@@ -2811,6 +2859,8 @@ static int analyzeAggregate(Walker *pWalker, Expr *pExpr){
switch( pExpr->op ){
case TK_AGG_COLUMN:
case TK_COLUMN: {
testcase( pExpr->op==TK_AGG_COLUMN );
testcase( pExpr->op==TK_COLUMN );
/* Check to see if the column is in one of the tables in the FROM
** clause of the aggregate query */
if( pSrcList ){