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Factor out the code that tries to avoid evaluating subquery operands if the

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other operand is NULL into a subroutine, so that it can be more easily reused
by other parts of the code generator.

FossilOrigin-Name: 3c6c71bcea16443b82234414137dfa1b59e2ee8fe5097906c738fc1228fec4e6
This commit is contained in:
drh
2025-06-30 10:30:47 +00:00
parent 311d73efc2
commit e24f20a4f5
3 changed files with 91 additions and 61 deletions
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15
manifest
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@@ -1,5 +1,5 @@
C Improve\sthe\sbytecode\sgenerated\sfor\scomparisons\sso\sthat\sif\sone\soperand\sis\na\ssubquery\sand\sthe\sother\soperand\sevaluates\sto\sNULL,\sthe\ssubquery\soperand\nis\snot\seven\scomputed.\s\sThis\sfixes\s5\sof\sthe\s12\sslow\squeries\sdescribed\nin\s[forum:/forumpost/52651713ac|forum\spost\s52651713ac].
D 2025-06-28T17:59:15.236
C Factor\sout\sthe\scode\sthat\stries\sto\savoid\sevaluating\ssubquery\soperands\sif\sthe\nother\soperand\sis\sNULL\sinto\sa\ssubroutine,\sso\sthat\sit\scan\sbe\smore\seasily\sreused\nby\sother\sparts\sof\sthe\scode\sgenerator.
D 2025-06-30T10:30:47.908
F .fossil-settings/binary-glob 61195414528fb3ea9693577e1980230d78a1f8b0a54c78cf1b9b24d0a409ed6a x
F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
@@ -736,7 +736,7 @@ F src/date.c 9db4d604e699a73e10b8e85a44db074a1f04c0591a77e2abfd77703f50dce1e9
F src/dbpage.c b3e218f8ed74fcbb7fa805df8ca669a3718d397617b3d8a8aac3307dc315c4d6
F src/dbstat.c 73362c0df0f40ad5523a6f5501224959d0976757b511299bf892313e79d14f5c
F src/delete.c 03a77ba20e54f0f42ebd8eddf15411ed6bdb06a2c472ac4b6b336521bf7cea42
F src/expr.c b46621069e36a2fbc966215691e4775134e2cc6c7a6e9e54b01cbb70b51d57a5
F src/expr.c f007ab177a9900d10893a58bf6b756e89144df635bab61b25f37a17390f12778
F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
F src/fkey.c 928ed2517e8732113d2b9821aa37af639688d752f4ea9ac6e0e393d713eeb76f
F src/func.c de47a8295503aa130baae5e6d9868ecf4f7c4dbffa65d83ad1f70bdbac0ee2d6
@@ -2208,11 +2208,8 @@ F tool/version-info.c 3b36468a90faf1bbd59c65fd0eb66522d9f941eedd364fabccd7227350
F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee87c1b31a7
F tool/warnings.sh 1ad0169b022b280bcaaf94a7fa231591be96b514230ab5c98fbf15cd7df842dd
F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
P 5508b56fd24016c13981ec280ecdd833007c9d8dd595edb295b984c2b487b5c8
R c5ec83310afc6f17c7231575eaf1e606
T *branch * optimize-null-values
T *sym-optimize-null-values *
T -sym-trunk *
P f147bc04776ac0056412f69dfc518016c0d5b4e9d964664e3d88f595fb29dbe0
R 2a36b21b6d3bc1bf7db15e8f66e788a3
U drh
Z 4eeee81d77d56831be900c22e39d8eec
Z 4ecc3e0b30247a36c4e1fea0e6dc5b85
# Remove this line to create a well-formed Fossil manifest.

2
manifest.uuid
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@@ -1 +1 @@
f147bc04776ac0056412f69dfc518016c0d5b4e9d964664e3d88f595fb29dbe0
3c6c71bcea16443b82234414137dfa1b59e2ee8fe5097906c738fc1228fec4e6

135
src/expr.c
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@@ -5830,6 +5830,67 @@ static void exprCodeBetween(
testcase( xJump==0 );
}
/*
** Compute the two operands of a binary operator.
**
** If either operand contains a subquery, then the code strives to
** compute the operand containing the subquery second. If the other
** operand evalutes to NULL, then a jump is made. The address of the
** IsNull operand that does this jump is returned. The caller can use
** this to optimize the computation so as to avoid doing the potentially
** expensive subquery.
**
** If no optimization opportunities exist, return 0.
*/
static int exprComputeOperands(
Parse *pParse, /* Parsing context */
Expr *pExpr, /* The comparison expression */
int *pR1, /* OUT: Register holding the left operand */
int *pR2, /* OUT: Register holding the right operand */
int *pFree1, /* OUT: Temp register to free if not zero */
int *pFree2 /* OUT: Another temp register to free if not zero */
){
int addrIsNull;
int r1, r2;
Vdbe *v = pParse->pVdbe;
assert( v!=0 );
/*
** If the left operand contains a (possibly expensive) subquery and the
** right operand does not and the right operation might be NULL,
** then compute the right operand first and do an IsNull jump if the
** right operand evalutes to NULL.
*/
if( ExprHasProperty(pExpr->pLeft, EP_Subquery)
&& !ExprHasProperty(pExpr->pRight, EP_Subquery)
&& sqlite3ExprCanBeNull(pExpr->pRight)
){
r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, pFree2);
addrIsNull = sqlite3VdbeAddOp1(v, OP_IsNull, r2); VdbeCoverage(v);
}else{
addrIsNull = 0;
}
r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, pFree1);
if( addrIsNull==0 ){
/*
** If the right operand contains a subquery and the left operand does not
** and the left operand might be NULL, then check the left operand do
** an IsNull check on the left operand before computing the right
** operand.
*/
if( ExprHasProperty(pExpr->pRight, EP_Subquery)
&& sqlite3ExprCanBeNull(pExpr->pLeft)
){
addrIsNull = sqlite3VdbeAddOp1(v, OP_IsNull, r1); VdbeCoverage(v);
}
r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, pFree2);
}
*pR1 = r1;
*pR2 = r2;
return addrIsNull;
}
/*
** Generate code for a boolean expression such that a jump is made
** to the label "dest" if the expression is true but execution
@@ -6076,75 +6137,47 @@ void sqlite3ExprIfFalse(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){
break;
}
case TK_IS:
case TK_ISNOT:
case TK_ISNOT: {
testcase( pExpr->op==TK_IS );
testcase( pExpr->op==TK_ISNOT );
if( sqlite3ExprIsVector(pExpr->pLeft) ) goto default_expr;
op = (pExpr->op==TK_IS) ? TK_NE : TK_EQ;
jumpIfNull = SQLITE_NULLEQ;
/* no break */ deliberate_fall_through
r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
r1, r2, dest, SQLITE_NULLEQ,
ExprHasProperty(pExpr,EP_Commuted));
testcase(op==OP_Eq); VdbeCoverageIf(v,op==OP_Eq);
testcase(op==OP_Ne); VdbeCoverageIf(v,op==OP_Ne);
break;
}
case TK_LT:
case TK_LE:
case TK_GT:
case TK_GE:
case TK_NE:
case TK_EQ: {
int r2Done = 0;
int addrBypass = 0;
int addrIsNull;
if( sqlite3ExprIsVector(pExpr->pLeft) ) goto default_expr;
testcase( jumpIfNull==0 );
/*
** If the left operand is a (possibly expensive) subquery and the
** right operand is not and the right operation might be NULL and
** the operator is not IS or IS NOT, then compute the right operand
** first and skip the computation of the left operand if the right
** operand is NULL.
*/
if( jumpIfNull!=SQLITE_NULLEQ
&& ExprHasProperty(pExpr->pLeft, EP_Subquery)
&& !ExprHasProperty(pExpr->pRight, EP_Subquery)
&& sqlite3ExprCanBeNull(pExpr->pRight)
){
r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
addrBypass = sqlite3VdbeAddOp2(v, OP_IsNull, r2, dest);
VdbeCoverageIf(v, jumpIfNull==SQLITE_JUMPIFNULL);
VdbeCoverageIf(v, jumpIfNull!=SQLITE_JUMPIFNULL);
if( jumpIfNull==SQLITE_JUMPIFNULL ) addrBypass = 0;
r2Done = 1;
}
r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
if( !r2Done ){
/*
** If the right operand is a subquery and the left operand is not
** and the left operand might be NULL and the comparison operator
** is not IS or IS NOT, then check the left operand to see if it is
** NULL and skip the computation of the right operand if it is.
*/
if( jumpIfNull!=SQLITE_NULLEQ
&& ExprHasProperty(pExpr->pRight, EP_Subquery)
&& sqlite3ExprCanBeNull(pExpr->pLeft)
){
addrBypass = sqlite3VdbeAddOp2(v, OP_IsNull, r1, dest);
VdbeCoverageIf(v, jumpIfNull==SQLITE_JUMPIFNULL);
VdbeCoverageIf(v, jumpIfNull!=SQLITE_JUMPIFNULL);
if( jumpIfNull==SQLITE_JUMPIFNULL ) addrBypass = 0;
}
r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
}
addrIsNull = exprComputeOperands(pParse, pExpr,
&r1, &r2, &regFree1, &regFree2);
codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
r1, r2, dest, jumpIfNull,ExprHasProperty(pExpr,EP_Commuted));
assert(TK_LT==OP_Lt); testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
assert(TK_LE==OP_Le); testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
assert(TK_GT==OP_Gt); testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
assert(TK_GE==OP_Ge); testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
assert(TK_EQ==OP_Eq); testcase(op==OP_Eq);
VdbeCoverageIf(v, op==OP_Eq && jumpIfNull!=SQLITE_NULLEQ);
VdbeCoverageIf(v, op==OP_Eq && jumpIfNull==SQLITE_NULLEQ);
assert(TK_NE==OP_Ne); testcase(op==OP_Ne);
VdbeCoverageIf(v, op==OP_Ne && jumpIfNull!=SQLITE_NULLEQ);
VdbeCoverageIf(v, op==OP_Ne && jumpIfNull==SQLITE_NULLEQ);
assert(TK_EQ==OP_Eq); testcase(op==OP_Eq); VdbeCoverageIf(v,op==OP_Eq);
assert(TK_NE==OP_Ne); testcase(op==OP_Ne); VdbeCoverageIf(v,op==OP_Ne);
testcase( regFree1==0 );
testcase( regFree2==0 );
if( addrBypass ) sqlite3VdbeJumpHere(v, addrBypass);
if( addrIsNull ){
if( jumpIfNull ){
sqlite3VdbeChangeP2(v, addrIsNull, dest);
}else{
sqlite3VdbeJumpHere(v, addrIsNull);
}
}
break;
}
case TK_ISNULL: