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Rearrange the implementation of index-only scans.

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This commit changes index-only scans so that data is read directly from the
index tuple without first generating a faux heap tuple.  The only immediate
benefit is that indexes on system columns (such as OID) can be used in
index-only scans, but this is necessary infrastructure if we are ever to
support index-only scans on expression indexes.  The executor is now ready
for that, though the planner still needs substantial work to recognize
the possibility.

To do this, Vars in index-only plan nodes have to refer to index columns
not heap columns.  I introduced a new special varno, INDEX_VAR, to mark
such Vars to avoid confusion.  (In passing, this commit renames the two
existing special varnos to OUTER_VAR and INNER_VAR.)  This allows
ruleutils.c to handle them with logic similar to what we use for subplan
reference Vars.

Since index-only scans are now fundamentally different from regular
indexscans so far as their expression subtrees are concerned, I also chose
to change them to have their own plan node type (and hence, their own
executor source file).
This commit is contained in:
Tom Lane
2011-10-11 14:20:06 -04:00
parent fa351d5a0d
commit a0185461dd
34 changed files with 1312 additions and 419 deletions
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26
src/include/executor/nodeIndexonlyscan.h Normal file
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/*-------------------------------------------------------------------------
*
* nodeIndexonlyscan.h
*
*
*
* Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/executor/nodeIndexonlyscan.h
*
*-------------------------------------------------------------------------
*/
#ifndef NODEINDEXONLYSCAN_H
#define NODEINDEXONLYSCAN_H
#include "nodes/execnodes.h"
extern IndexOnlyScanState *ExecInitIndexOnlyScan(IndexOnlyScan *node, EState *estate, int eflags);
extern TupleTableSlot *ExecIndexOnlyScan(IndexOnlyScanState *node);
extern void ExecEndIndexOnlyScan(IndexOnlyScanState *node);
extern void ExecIndexOnlyMarkPos(IndexOnlyScanState *node);
extern void ExecIndexOnlyRestrPos(IndexOnlyScanState *node);
extern void ExecReScanIndexOnlyScan(IndexOnlyScanState *node);
#endif /* NODEINDEXONLYSCAN_H */