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Provide hints to the btree layer Next and Previous primitives to let them

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know if they can be no-ops if the underlying index is unique.

FossilOrigin-Name: 6c643e45c274e755dc5a1a65673df79261c774be
This commit is contained in:
drh
2014-02-03 14:04:11 +00:00
parent 6645370e5b
commit e39a732ce2
6 changed files with 62 additions and 25 deletions
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23
src/vdbe.c
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@@ -3599,6 +3599,7 @@ case OP_SeekGt: { /* jump, in3 */
#endif
if( oc>=OP_SeekGe ){ assert( oc==OP_SeekGe || oc==OP_SeekGt );
if( res<0 || (res==0 && oc==OP_SeekGt) ){
res = 0;
rc = sqlite3BtreeNext(pC->pCursor, &res);
if( rc!=SQLITE_OK ) goto abort_due_to_error;
pC->rowidIsValid = 0;
@@ -3608,6 +3609,7 @@ case OP_SeekGt: { /* jump, in3 */
}else{
assert( oc==OP_SeekLt || oc==OP_SeekLe );
if( res>0 || (res==0 && oc==OP_SeekLt) ){
res = 0;
rc = sqlite3BtreePrevious(pC->pCursor, &res);
if( rc!=SQLITE_OK ) goto abort_due_to_error;
pC->rowidIsValid = 0;
@@ -4460,7 +4462,7 @@ case OP_Rewind: { /* jump */
break;
}
/* Opcode: Next P1 P2 * * P5
/* Opcode: Next P1 P2 P3 * P5
**
** Advance cursor P1 so that it points to the next key/data pair in its
** table or index. If there are no more key/value pairs then fall through
@@ -4470,6 +4472,11 @@ case OP_Rewind: { /* jump */
** The P1 cursor must be for a real table, not a pseudo-table. P1 must have
** been opened prior to this opcode or the program will segfault.
**
** The P3 value is a hint to the btree implementation. If P3==1, that
** means P1 is an SQL index and that this instruction could have been
** omitted if that index had been unique. P3 is usually 0. P3 is
** always either 0 or 1.
**
** P4 is always of type P4_ADVANCE. The function pointer points to
** sqlite3BtreeNext().
**
@@ -4478,12 +4485,12 @@ case OP_Rewind: { /* jump */
**
** See also: Prev, NextIfOpen
*/
/* Opcode: NextIfOpen P1 P2 * * P5
/* Opcode: NextIfOpen P1 P2 P3 * P5
**
** This opcode works just like OP_Next except that if cursor P1 is not
** open it behaves a no-op.
*/
/* Opcode: Prev P1 P2 * * P5
/* Opcode: Prev P1 P2 P3 * P5
**
** Back up cursor P1 so that it points to the previous key/data pair in its
** table or index. If there is no previous key/value pairs then fall through
@@ -4493,13 +4500,18 @@ case OP_Rewind: { /* jump */
** The P1 cursor must be for a real table, not a pseudo-table. If P1 is
** not open then the behavior is undefined.
**
** The P3 value is a hint to the btree implementation. If P3==1, that
** means P1 is an SQL index and that this instruction could have been
** omitted if that index had been unique. P3 is usually 0. P3 is
** always either 0 or 1.
**
** P4 is always of type P4_ADVANCE. The function pointer points to
** sqlite3BtreePrevious().
**
** If P5 is positive and the jump is taken, then event counter
** number P5-1 in the prepared statement is incremented.
*/
/* Opcode: PrevIfOpen P1 P2 * * P5
/* Opcode: PrevIfOpen P1 P2 P3 * P5
**
** This opcode works just like OP_Prev except that if cursor P1 is not
** open it behaves a no-op.
@@ -4521,9 +4533,12 @@ case OP_Next: /* jump */
assert( pOp->p1>=0 && pOp->p1<p->nCursor );
assert( pOp->p5<ArraySize(p->aCounter) );
pC = p->apCsr[pOp->p1];
res = pOp->p3;
assert( pC!=0 );
assert( pC->deferredMoveto==0 );
assert( pC->pCursor );
assert( res==0 || (res==1 && pC->isTable==0) );
testcase( res==1 );
assert( pOp->opcode!=OP_Next || pOp->p4.xAdvance==sqlite3BtreeNext );
assert( pOp->opcode!=OP_Prev || pOp->p4.xAdvance==sqlite3BtreePrevious );
assert( pOp->opcode!=OP_NextIfOpen || pOp->p4.xAdvance==sqlite3BtreeNext );