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If the SQLITE_ENABLE_CURSOR_HINTS macro is defined, then invoke the

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sqlite3BtreeCursorHint() interface to provide hints to the storage engine
about rows that need not be returned.  Hints can be disabled using
SQLITE_TESTCTRL_OPTIMIZATIONS with SQLITE_CursorHints (0x2000).  Cursor
hints are not used by the built-in storage engine of SQLite but might
be useful to applications that provide their own storage engine.  The
current code is work-in-progrss and contains bugs.

FossilOrigin-Name: 3a9bec524ef2de44028b4058e67dc962082888d3
This commit is contained in:
drh
2013-12-07 20:39:19 +00:00
parent 9dcc7cd527
commit 28935364ef
9 changed files with 124 additions and 13 deletions
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18
src/vdbe.c
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@@ -6170,6 +6170,24 @@ case OP_Trace: {
}
#endif
#ifdef SQLITE_ENABLE_CURSOR_HINTS
/* Opcode: CursorHint P1 P2 * P4 *
**
** Provide a hint to cursor P1 that it only needs to return rows that
** satisfy the Expr tree given in P4. P2 is the table number of cursor P1
** such that references to cursor P1 in the Expr tree are given by
** Expr.iTable==P2.
*/
case OP_CursorHint: {
VdbeCursor *pC;
assert( pOp->p1>=0 && pOp->p1<p->nCursor );
assert( pOp->p4type==P4_EXPR );
pC = p->apCsr[pOp->p1];
if( pC ) sqlite3BtreeCursorHint(pC->pCursor, pOp->p2, pOp->p4.pExpr);
break;
}
#endif /* SQLITE_ENABLE_CURSOR_HINTS */
/* Opcode: Noop * * * * *
**