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Reuse the same materialization of a view when that view appears in a query

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more than once, such as in a self-join.

FossilOrigin-Name: 9e35c89dbe744312f612e507b51ff9a5bb656def75392d25bc19fc638548cd1e
This commit is contained in:
drh
2017-05-02 17:54:19 +00:00
parent a1f5c0c90b ed71298085
commit 3f4df4c6f3
5 changed files with 79 additions and 15 deletions
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31
src/vdbe.c
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@@ -3540,6 +3540,37 @@ open_cursor_set_hints:
break;
}
/* Opcode: OpenDup P1 P2 * * *
**
** Open a new cursor P1 that points to the same ephemeral table as
** cursor P2. The P2 cursor must have been opened by a prior OP_OpenEphemeral
** opcode. Only ephemeral cursors may be duplicated.
**
** Duplicate ephemeral cursors are used for self-joins of materialized views.
*/
case OP_OpenDup: {
VdbeCursor *pOrig; /* The original cursor to be duplicated */
VdbeCursor *pCx; /* The new cursor */
pOrig = p->apCsr[pOp->p2];
assert( pOrig->pBtx!=0 ); /* Only ephemeral cursors can be duplicated */
pCx = allocateCursor(p, pOp->p1, pOrig->nField, -1, CURTYPE_BTREE);
if( pCx==0 ) goto no_mem;
pCx->nullRow = 1;
pCx->isEphemeral = 1;
pCx->pKeyInfo = pOrig->pKeyInfo;
pCx->isTable = pOrig->isTable;
rc = sqlite3BtreeCursor(pOrig->pBtx, MASTER_ROOT, BTREE_WRCSR,
pCx->pKeyInfo, pCx->uc.pCursor);
/* The sqlite3BtreeCursor() routine can only fail for the first cursor
** opened for a database. Since there is already an open cursor when this
** opcode is run, the sqlite3BtreeCursor() cannot fail */
assert( rc==SQLITE_OK );
break;
}
/* Opcode: OpenEphemeral P1 P2 * P4 P5
** Synopsis: nColumn=P2
**