database/sqlite
1
0
Fork 0
mirror of https://github.com/sqlite/sqlite.git synced 2025-11-12 13:01:09 +03:00
Code Activity

Rework the logic that factors constant expressions out of inner loops, making

Browse Source 
it both simpler and faster.

FossilOrigin-Name: 8dc5c76c766828d7c28090bec30ff48227e7b140
This commit is contained in:
drh
2013-11-15 01:10:18 +00:00
parent 01752bc805
commit f30a969b80
11 changed files with 82 additions and 167 deletions
Download Patch File Download Diff File Expand all files Collapse all files

175
src/expr.c
View File

@@ -2989,15 +2989,42 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
** If the register is a temporary register that can be deallocated,
** then write its number into *pReg. If the result register is not
** a temporary, then set *pReg to zero.
**
** If pExpr is a constant, then this routine might generate this
** code to fill the register in the initialization section of the
** VDBE program, in order to factor it out of the evaluation loop.
*/
int sqlite3ExprCodeTemp(Parse *pParse, Expr *pExpr, int *pReg){
int r1 = sqlite3GetTempReg(pParse);
int r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
if( r2==r1 ){
*pReg = r1;
int r2;
pExpr = sqlite3ExprSkipCollate(pExpr);
if( pParse->cookieGoto>0
&& pParse->nMem<32768
&& pExpr->op!=TK_REGISTER
&& sqlite3ExprIsConstantNotJoin(pExpr)
){
ExprList *p = pParse->pConstExpr;
int i;
*pReg = 0;
if( p ){
for(i=0; i<p->nExpr; i++){
if( sqlite3ExprCompare(p->a[i].pExpr, pExpr, -1)==0 ){
return p->a[i].iAlias;
}
}
}
p = sqlite3ExprListAppend(pParse, p, sqlite3ExprDup(pParse->db, pExpr, 0));
pParse->pConstExpr = p;
r2 = ++pParse->nMem;
if( p ) p->a[p->nExpr-1].iAlias = r2;
}else{
sqlite3ReleaseTempReg(pParse, r1);
*pReg = 0;
int r1 = sqlite3GetTempReg(pParse);
r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
if( r2==r1 ){
*pReg = r1;
}else{
sqlite3ReleaseTempReg(pParse, r1);
*pReg = 0;
}
}
return r2;
}
@@ -3328,140 +3355,6 @@ void sqlite3ExplainExprList(Vdbe *pOut, ExprList *pList){
}
#endif /* SQLITE_DEBUG */
/*
** Return TRUE if pExpr is an constant expression that is appropriate
** for factoring out of a loop. Appropriate expressions are:
**
** * Any expression that evaluates to two or more opcodes.
**
** * Any OP_Integer, OP_Real, OP_String, OP_Blob, OP_Null,
** or OP_Variable that does not need to be placed in a
** specific register.
**
** There is no point in factoring out single-instruction constant
** expressions that need to be placed in a particular register.
** We could factor them out, but then we would end up adding an
** OP_SCopy instruction to move the value into the correct register
** later. We might as well just use the original instruction and
** avoid the OP_SCopy.
*/
static int isAppropriateForFactoring(Expr *p){
if( !sqlite3ExprIsConstantNotJoin(p) ){
return 0; /* Only constant expressions are appropriate for factoring */
}
if( (p->flags & EP_FixedDest)==0 ){
return 1; /* Any constant without a fixed destination is appropriate */
}
while( p->op==TK_UPLUS ) p = p->pLeft;
switch( p->op ){
#ifndef SQLITE_OMIT_BLOB_LITERAL
case TK_BLOB:
#endif
case TK_VARIABLE:
case TK_INTEGER:
case TK_FLOAT:
case TK_NULL:
case TK_STRING: {
testcase( p->op==TK_BLOB );
testcase( p->op==TK_VARIABLE );
testcase( p->op==TK_INTEGER );
testcase( p->op==TK_FLOAT );
testcase( p->op==TK_NULL );
testcase( p->op==TK_STRING );
/* Single-instruction constants with a fixed destination are
** better done in-line. If we factor them, they will just end
** up generating an OP_SCopy to move the value to the destination
** register. */
return 0;
}
case TK_UMINUS: {
if( p->pLeft->op==TK_FLOAT || p->pLeft->op==TK_INTEGER ){
return 0;
}
break;
}
default: {
break;
}
}
return 1;
}
/*
** If pExpr is a constant expression that is appropriate for
** factoring out of a loop, then evaluate the expression
** into a register and convert the expression into a TK_REGISTER
** expression.
*/
static int evalConstExpr(Walker *pWalker, Expr *pExpr){
Parse *pParse = pWalker->pParse;
switch( pExpr->op ){
case TK_IN:
case TK_REGISTER: {
return WRC_Prune;
}
case TK_COLLATE: {
return WRC_Continue;
}
case TK_FUNCTION:
case TK_AGG_FUNCTION:
case TK_CONST_FUNC: {
/* The arguments to a function have a fixed destination.
** Mark them this way to avoid generated unneeded OP_SCopy
** instructions.
*/
ExprList *pList = pExpr->x.pList;
assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
if( pList ){
int i = pList->nExpr;
struct ExprList_item *pItem = pList->a;
for(; i>0; i--, pItem++){
if( ALWAYS(pItem->pExpr) ) pItem->pExpr->flags |= EP_FixedDest;
}
}
break;
}
}
if( isAppropriateForFactoring(pExpr) ){
int r1 = ++pParse->nMem;
int r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
/* If r2!=r1, it means that register r1 is never used. That is harmless
** but suboptimal, so we want to know about the situation to fix it.
** Hence the following assert: */
assert( r2==r1 );
exprToRegister(pExpr, r2);
return WRC_Prune;
}
return WRC_Continue;
}
/*
** Preevaluate constant subexpressions within pExpr and store the
** results in registers. Modify pExpr so that the constant subexpresions
** are TK_REGISTER opcodes that refer to the precomputed values.
**
** This routine is a no-op if the jump to the cookie-check code has
** already occur. Since the cookie-check jump is generated prior to
** any other serious processing, this check ensures that there is no
** way to accidently bypass the constant initializations.
**
** This routine is also a no-op if the SQLITE_FactorOutConst optimization
** is disabled via the sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS)
** interface. This allows test logic to verify that the same answer is
** obtained for queries regardless of whether or not constants are
** precomputed into registers or if they are inserted in-line.
*/
void sqlite3ExprCodeConstants(Parse *pParse, Expr *pExpr){
Walker w;
if( pParse->cookieGoto ) return;
if( OptimizationDisabled(pParse->db, SQLITE_FactorOutConst) ) return;
memset(&w, 0, sizeof(w));
w.xExprCallback = evalConstExpr;
w.pParse = pParse;
sqlite3WalkExpr(&w, pExpr);
}
/*
** Generate code that pushes the value of every element of the given
** expression list into a sequence of registers beginning at target.
@@ -3863,7 +3756,7 @@ int sqlite3ExprCompare(Expr *pA, Expr *pB, int iTab){
if( pA->iColumn!=pB->iColumn ) return 2;
if( pA->iTable!=pB->iTable
&& pA->op!=TK_REGISTER
&& (pA->iTable!=iTab || NEVER(pB->iTable>=0)) ) return 2;
&& (pA->iTable!=iTab || pB->iTable>=0) ) return 2;
if( ExprHasProperty(pA, EP_IntValue) ){
if( !ExprHasProperty(pB, EP_IntValue) || pA->u.iValue!=pB->u.iValue ){
return 2;