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Instrument index-only scans to count heap fetches performed.

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Patch by me; review by Tom Lane, Jeff Davis, and Peter Geoghegan.
This commit is contained in:
Robert Haas 2012-01-25 20:40:34 -05:00
parent 08146775ac
commit 9f9135d129
3 changed files with 7 additions and 0 deletions
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3
src/backend/commands/explain.c
View File

@ -1012,6 +1012,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
if (plan->qual)
show_instrumentation_count("Rows Removed by Filter", 1,
planstate, es);
if (es->analyze)
ExplainPropertyLong("Heap Fetches",
((IndexOnlyScanState *) planstate)->ioss_HeapFetches, es);
break;
case T_BitmapIndexScan:
show_scan_qual(((BitmapIndexScan *) plan)->indexqualorig,

2
src/backend/executor/nodeIndexonlyscan.c
View File

@ -90,6 +90,7 @@ IndexOnlyNext(IndexOnlyScanState *node)
/*
* Rats, we have to visit the heap to check visibility.
*/
node->ioss_HeapFetches++;
tuple = index_fetch_heap(scandesc);
if (tuple == NULL)
continue; /* no visible tuple, try next index entry */
@ -346,6 +347,7 @@ ExecInitIndexOnlyScan(IndexOnlyScan *node, EState *estate, int eflags)
indexstate = makeNode(IndexOnlyScanState);
indexstate->ss.ps.plan = (Plan *) node;
indexstate->ss.ps.state = estate;
indexstate->ioss_HeapFetches = 0;
/*
* Miscellaneous initialization

2
src/include/nodes/execnodes.h
View File

@ -1260,6 +1260,7 @@ typedef struct IndexScanState
* RelationDesc index relation descriptor
* ScanDesc index scan descriptor
* VMBuffer buffer in use for visibility map testing, if any
* HeapFetches number of tuples we were forced to fetch from heap
* ----------------
*/
typedef struct IndexOnlyScanState
@ -1277,6 +1278,7 @@ typedef struct IndexOnlyScanState
Relation ioss_RelationDesc;
IndexScanDesc ioss_ScanDesc;
Buffer ioss_VMBuffer;
long ioss_HeapFetches;
} IndexOnlyScanState;
/* ----------------