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Rearrange the implementation of index-only scans.

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

View File

@@ -26,6 +26,7 @@
#include "executor/nodeGroup.h"
#include "executor/nodeHash.h"
#include "executor/nodeHashjoin.h"
#include "executor/nodeIndexonlyscan.h"
#include "executor/nodeIndexscan.h"
#include "executor/nodeLimit.h"
#include "executor/nodeLockRows.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
ExecReScanIndexScan((IndexScanState *) node);
break;
case T_IndexOnlyScanState:
ExecReScanIndexOnlyScan((IndexOnlyScanState *) node);
break;
case T_BitmapIndexScanState:
ExecReScanBitmapIndexScan((BitmapIndexScanState *) node);
break;
@@ -273,6 +278,10 @@ ExecMarkPos(PlanState *node)
ExecIndexMarkPos((IndexScanState *) node);
break;
case T_IndexOnlyScanState:
ExecIndexOnlyMarkPos((IndexOnlyScanState *) node);
break;
case T_TidScanState:
ExecTidMarkPos((TidScanState *) node);
break;
@@ -326,6 +335,10 @@ ExecRestrPos(PlanState *node)
ExecIndexRestrPos((IndexScanState *) node);
break;
case T_IndexOnlyScanState:
ExecIndexOnlyRestrPos((IndexOnlyScanState *) node);
break;
case T_TidScanState:
ExecTidRestrPos((TidScanState *) node);
break;
@@ -371,6 +384,7 @@ ExecSupportsMarkRestore(NodeTag plantype)
{
case T_SeqScan:
case T_IndexScan:
case T_IndexOnlyScan:
case T_TidScan:
case T_ValuesScan:
case T_Material:
@@ -442,6 +456,10 @@ ExecSupportsBackwardScan(Plan *node)
return IndexSupportsBackwardScan(((IndexScan *) node)->indexid) &&
TargetListSupportsBackwardScan(node->targetlist);
case T_IndexOnlyScan:
return IndexSupportsBackwardScan(((IndexOnlyScan *) node)->indexid) &&
TargetListSupportsBackwardScan(node->targetlist);
case T_SubqueryScan:
return ExecSupportsBackwardScan(((SubqueryScan *) node)->subplan) &&
TargetListSupportsBackwardScan(node->targetlist);
@@ -474,7 +492,8 @@ TargetListSupportsBackwardScan(List *targetlist)
}
/*
* An IndexScan node supports backward scan only if the index's AM does.
* An IndexScan or IndexOnlyScan node supports backward scan only if the
* index's AM does.
*/
static bool
IndexSupportsBackwardScan(Oid indexid)