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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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119
src/backend/commands/explain.c
View File

@ -79,6 +79,8 @@ static void show_instrumentation_count(const char *qlabel, int which,
PlanState *planstate, ExplainState *es);
static void show_foreignscan_info(ForeignScanState *fsstate, ExplainState *es);
static const char *explain_get_index_name(Oid indexId);
static void ExplainIndexScanDetails(Oid indexid, ScanDirection indexorderdir,
ExplainState *es);
static void ExplainScanTarget(Scan *plan, ExplainState *es);
static void ExplainModifyTarget(ModifyTable *plan, ExplainState *es);
static void ExplainTargetRel(Plan *plan, Index rti, ExplainState *es);
@ -656,10 +658,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
pname = sname = "Seq Scan";
break;
case T_IndexScan:
if (((IndexScan *) plan)->indexonly)
pname = sname = "Index Only Scan";
else
pname = sname = "Index Scan";
pname = sname = "Index Scan";
break;
case T_IndexOnlyScan:
pname = sname = "Index Only Scan";
break;
case T_BitmapIndexScan:
pname = sname = "Bitmap Index Scan";
@ -793,42 +795,6 @@ ExplainNode(PlanState *planstate, List *ancestors,
switch (nodeTag(plan))
{
case T_IndexScan:
{
IndexScan *indexscan = (IndexScan *) plan;
const char *indexname =
explain_get_index_name(indexscan->indexid);
if (es->format == EXPLAIN_FORMAT_TEXT)
{
if (ScanDirectionIsBackward(indexscan->indexorderdir))
appendStringInfoString(es->str, " Backward");
appendStringInfo(es->str, " using %s", indexname);
}
else
{
const char *scandir;
switch (indexscan->indexorderdir)
{
case BackwardScanDirection:
scandir = "Backward";
break;
case NoMovementScanDirection:
scandir = "NoMovement";
break;
case ForwardScanDirection:
scandir = "Forward";
break;
default:
scandir = "???";
break;
}
ExplainPropertyText("Scan Direction", scandir, es);
ExplainPropertyText("Index Name", indexname, es);
}
}
/* FALL THRU */
case T_SeqScan:
case T_BitmapHeapScan:
case T_TidScan:
@ -840,6 +806,26 @@ ExplainNode(PlanState *planstate, List *ancestors,
case T_ForeignScan:
ExplainScanTarget((Scan *) plan, es);
break;
case T_IndexScan:
{
IndexScan *indexscan = (IndexScan *) plan;
ExplainIndexScanDetails(indexscan->indexid,
indexscan->indexorderdir,
es);
ExplainScanTarget((Scan *) indexscan, es);
}
break;
case T_IndexOnlyScan:
{
IndexOnlyScan *indexonlyscan = (IndexOnlyScan *) plan;
ExplainIndexScanDetails(indexonlyscan->indexid,
indexonlyscan->indexorderdir,
es);
ExplainScanTarget((Scan *) indexonlyscan, es);
}
break;
case T_BitmapIndexScan:
{
BitmapIndexScan *bitmapindexscan = (BitmapIndexScan *) plan;
@ -1014,6 +1000,19 @@ ExplainNode(PlanState *planstate, List *ancestors,
show_instrumentation_count("Rows Removed by Filter", 1,
planstate, es);
break;
case T_IndexOnlyScan:
show_scan_qual(((IndexOnlyScan *) plan)->indexqual,
"Index Cond", planstate, ancestors, es);
if (((IndexOnlyScan *) plan)->indexqual)
show_instrumentation_count("Rows Removed by Index Recheck", 2,
planstate, es);
show_scan_qual(((IndexOnlyScan *) plan)->indexorderby,
"Order By", planstate, ancestors, es);
show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
if (plan->qual)
show_instrumentation_count("Rows Removed by Filter", 1,
planstate, es);
break;
case T_BitmapIndexScan:
show_scan_qual(((BitmapIndexScan *) plan)->indexqualorig,
"Index Cond", planstate, ancestors, es);
@ -1626,6 +1625,45 @@ explain_get_index_name(Oid indexId)
return result;
}
/*
* Add some additional details about an IndexScan or IndexOnlyScan
*/
static void
ExplainIndexScanDetails(Oid indexid, ScanDirection indexorderdir,
ExplainState *es)
{
const char *indexname = explain_get_index_name(indexid);
if (es->format == EXPLAIN_FORMAT_TEXT)
{
if (ScanDirectionIsBackward(indexorderdir))
appendStringInfoString(es->str, " Backward");
appendStringInfo(es->str, " using %s", indexname);
}
else
{
const char *scandir;
switch (indexorderdir)
{
case BackwardScanDirection:
scandir = "Backward";
break;
case NoMovementScanDirection:
scandir = "NoMovement";
break;
case ForwardScanDirection:
scandir = "Forward";
break;
default:
scandir = "???";
break;
}
ExplainPropertyText("Scan Direction", scandir, es);
ExplainPropertyText("Index Name", indexname, es);
}
}
/*
* Show the target of a Scan node
*/
@ -1670,6 +1708,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
{
case T_SeqScan:
case T_IndexScan:
case T_IndexOnlyScan:
case T_BitmapHeapScan:
case T_TidScan:
case T_ForeignScan: