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Tighter VDBE code for the WHERE_DISTINCT_ORDERED case of DISTINCT keyword

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handling.

FossilOrigin-Name: 94b48064db3cbb43e911fdf7183218b08146ec10
This commit is contained in:
drh
2012-09-19 21:15:46 +00:00
parent ae651d614e
commit 053a128f55
6 changed files with 73 additions and 32 deletions
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29
src/vdbe.c
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@@ -956,23 +956,28 @@ case OP_String: { /* out2-prerelease */
break;
}
/* Opcode: Null * P2 P3 * *
/* Opcode: Null P1 P2 P3 * *
**
** Write a NULL into registers P2. If P3 greater than P2, then also write
** NULL into register P3 and ever register in between P2 and P3. If P3
** NULL into register P3 and every register in between P2 and P3. If P3
** is less than P2 (typically P3 is zero) then only register P2 is
** set to NULL
** set to NULL.
**
** If the P1 value is non-zero, then also set the MEM_Cleared flag so that
** NULL values will not compare equal even if SQLITE_NULLEQ is set on
** OP_Ne or OP_Eq.
*/
case OP_Null: { /* out2-prerelease */
int cnt;
u16 nullFlag;
cnt = pOp->p3-pOp->p2;
assert( pOp->p3<=p->nMem );
pOut->flags = MEM_Null;
pOut->flags = nullFlag = pOp->p1 ? (MEM_Null|MEM_Cleared) : MEM_Null;
while( cnt>0 ){
pOut++;
memAboutToChange(p, pOut);
VdbeMemRelease(pOut);
pOut->flags = MEM_Null;
pOut->flags = nullFlag;
cnt--;
}
break;
@@ -1737,6 +1742,10 @@ case OP_ToReal: { /* same as TK_TO_REAL, in1 */
**
** If the SQLITE_STOREP2 bit of P5 is set, then do not jump. Instead,
** store a boolean result (either 0, or 1, or NULL) in register P2.
**
** If the SQLITE_NULLEQ bit is set in P5, then NULL values are considered
** equal to one another, provided that they do not have their MEM_Cleared
** bit set.
*/
/* Opcode: Ne P1 P2 P3 P4 P5
**
@@ -1803,7 +1812,15 @@ case OP_Ge: { /* same as TK_GE, jump, in1, in3 */
** or not both operands are null.
*/
assert( pOp->opcode==OP_Eq || pOp->opcode==OP_Ne );
res = (flags1 & flags3 & MEM_Null)==0;
assert( (flags1 & MEM_Cleared)==0 );
if( (flags1&MEM_Null)!=0
&& (flags3&MEM_Null)!=0
&& (flags3&MEM_Cleared)==0
){
res = 0; /* Results are equal */
}else{
res = 1; /* Results are not equal */
}
}else{
/* SQLITE_NULLEQ is clear and at least one operand is NULL,
** then the result is always NULL.