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Replace the OP_SetIfNotPos operator with OP_OffsetLimit in the VDBE, for

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simpler and smaller code.

FossilOrigin-Name: 7ac017a498b6fb28343eef2d24e400c7800660d6
This commit is contained in:
drh
2016-01-25 15:57:29 +00:00
parent 164c957b09
commit cc2fa4cf55
4 changed files with 33 additions and 25 deletions
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33
src/vdbe.c
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@@ -5757,20 +5757,31 @@ case OP_IfPos: { /* jump, in1 */
break;
}
/* Opcode: SetIfNotPos P1 P2 P3 * *
** Synopsis: if r[P1]<=0 then r[P2]=P3
/* Opcode: OffsetLimit P1 P2 P3 * *
** Synopsis: if r[P1]>0 then r[P2]=r[P1]+max(0,r[P3]) else r[P2]=(-1)
**
** Register P1 must contain an integer.
** If the value of register P1 is not positive (if it is less than 1) then
** set the value of register P2 to be the integer P3.
** This opcode performs a commonly used computation associated with
** LIMIT and OFFSET process. r[P1] holds the limit counter. r[P3]
** holds the offset counter. The opcode computes the combined value
** of the LIMIT and OFFSET and stores that value in r[P2]. The r[P2]
** value computed is the total number of rows that will need to be
** visited in order to complete the query.
**
** If r[P3] is zero or negative, that means there is no OFFSET
** and r[P2] is set to be the value of the LIMIT, r[P1].
**
** if r[P1] is zero or negative, that means there is no LIMIT
** and r[P2] is set to -1.
**
** Otherwise, r[P2] is set to the sum of r[P1] and r[P3].
*/
case OP_SetIfNotPos: { /* in1, in2 */
case OP_OffsetLimit: { /* in1, out2, in3 */
pIn1 = &aMem[pOp->p1];
assert( pIn1->flags&MEM_Int );
if( pIn1->u.i<=0 ){
pOut = out2Prerelease(p, pOp);
pOut->u.i = pOp->p3;
}
pIn3 = &aMem[pOp->p3];
pOut = out2Prerelease(p, pOp);
assert( pIn1->flags & MEM_Int );
assert( pIn3->flags & MEM_Int );
pOut->u.i = pIn1->u.i<=0 ? -1 : pIn1->u.i+(pIn3->u.i>0?pIn3->u.i:0);
break;
}