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Add the OP_ReopenIdx opcode that works like OP_OpenRead except that it becomes

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a no-op if the cursor is already open on the same index.  Update the
OR-optimization logic to make use of OP_ReopenIdx in order to avoid
unnecessary cursor open requests sent to the B-Tree layer.

FossilOrigin-Name: 77f412caf0192d3e7fecb377d6d72123d8b64424
This commit is contained in:
drh
2014-07-22 20:02:19 +00:00
parent a45fdc7b1e
commit 3526319b48
6 changed files with 49 additions and 15 deletions
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33
src/vdbe.c
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@@ -3205,7 +3205,21 @@ case OP_SetCookie: { /* in3 */
** sequence of the index being opened. Otherwise, if P4 is an integer
** value, it is set to the number of columns in the table.
**
** See also OpenWrite.
** See also: OpenWrite, ReopenIdx
*/
/* Opcode: ReopenIdx P1 P2 P3 P4 P5
** Synopsis: root=P2 iDb=P3
**
** The ReopenIdx opcode works exactly like ReadOpen except that it first
** checks to see if the cursor on P1 is already open with a root page
** number of P2 and if it is this opcode becomes a no-op. In other words,
** if the cursor is already open, do not reopen it.
**
** The ReopenIdx opcode may only be used with P5==0 and with P4 being
** a P4_KEYINFO object. Furthermore, the P3 value must be the same as
** every other ReopenIdx or OpenRead for the same cursor number.
**
** See the OpenRead opcode documentation for additional information.
*/
/* Opcode: OpenWrite P1 P2 P3 P4 P5
** Synopsis: root=P2 iDb=P3
@@ -3227,6 +3241,19 @@ case OP_SetCookie: { /* in3 */
**
** See also OpenRead.
*/
case OP_ReopenIdx: {
VdbeCursor *pCur;
assert( pOp->p5==0 );
assert( pOp->p4type==P4_KEYINFO );
pCur = p->apCsr[pOp->p1];
if( pCur && pCur->pgnoRoot==pOp->p2 ){
assert( pCur->iDb==pOp->p3 ); /* Guaranteed by the code generator */
break;
}
/* If the cursor is not currently open or is open on a different
** index, then fall through into OP_OpenRead to force a reopen */
}
case OP_OpenRead:
case OP_OpenWrite: {
int nField;
@@ -3241,7 +3268,8 @@ case OP_OpenWrite: {
assert( (pOp->p5&(OPFLAG_P2ISREG|OPFLAG_BULKCSR))==pOp->p5 );
assert( pOp->opcode==OP_OpenWrite || pOp->p5==0 );
assert( p->bIsReader );
assert( pOp->opcode==OP_OpenRead || p->readOnly==0 );
assert( pOp->opcode==OP_OpenRead || pOp->opcode==OP_ReopenIdx
|| p->readOnly==0 );
if( p->expired ){
rc = SQLITE_ABORT;
@@ -3298,6 +3326,7 @@ case OP_OpenWrite: {
if( pCur==0 ) goto no_mem;
pCur->nullRow = 1;
pCur->isOrdered = 1;
pCur->pgnoRoot = p2;
rc = sqlite3BtreeCursor(pX, p2, wrFlag, pKeyInfo, pCur->pCursor);
pCur->pKeyInfo = pKeyInfo;
assert( OPFLAG_BULKCSR==BTREE_BULKLOAD );