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Commitb1fc51a

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Comment fixes for extended statistics
Clean up some code comments in new extended statistics code, from7b504eb.
1 parentdc0400c commitb1fc51a

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5 files changed

+15
-11
lines changed

5 files changed

+15
-11
lines changed

‎src/backend/optimizer/util/plancat.c

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -79,6 +79,7 @@ static List *get_relation_statistics(RelOptInfo *rel, Relation relation);
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*min_attrlowest valid AttrNumber
8080
*max_attrhighest valid AttrNumber
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*indexlistlist of IndexOptInfos for relation's indexes
82+
*statlistlist of StatisticExtInfo for relation's statistic objects
8283
*serveridif it's a foreign table, the server OID
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*fdwroutineif it's a foreign table, the FDW function pointers
8485
*pagesnumber of pages

‎src/backend/statistics/dependencies.c

Lines changed: 7 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -900,7 +900,13 @@ find_strongest_dependency(StatisticExtInfo * stats, MVDependencies * dependencie
900900

901901
/*
902902
* dependencies_clauselist_selectivity
903-
*Attempt to estimate selectivity using functional dependency statistics
903+
*Return the estimated selectivity of the given clauses using
904+
*functional dependency statistics, or 1.0 if no useful functional
905+
*dependency statistic exists.
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*
907+
* 'estimatedclauses' is an output argument that gets a bit set corresponding
908+
* to the (zero-based) list index of clauses that are included in the
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* estimated selectivity.
904910
*
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* Given equality clauses on attributes (a,b) we find the strongest dependency
906912
* between them, i.e. either (a=>b) or (b=>a). Assuming (a=>b) is the selected
@@ -935,7 +941,6 @@ dependencies_clauselist_selectivity(PlannerInfo *root,
935941
AttrNumber*list_attnums;
936942
intlistidx;
937943

938-
939944
/* check if there's any stats that might be useful for us. */
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if (!has_stats_of_kind(rel->statlist,STATS_EXT_DEPENDENCIES))
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return1.0;

‎src/backend/statistics/extended_stats.c

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -408,7 +408,7 @@ multi_sort_compare_dims(int start, int end,
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409409
/*
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* has_stats_of_kind
411-
*Check that the list contains statistic of a given kind
411+
*Check that the list contains statistic of a given kind
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*/
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bool
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has_stats_of_kind(List*stats,charrequiredkind)
@@ -428,8 +428,9 @@ has_stats_of_kind(List *stats, char requiredkind)
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429429
/*
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* choose_best_statistics
431-
*Look for statistics with the specified 'requiredkind' which have keys
432-
*that match at least two attnums.
431+
*Look for and return statistics with the specified 'requiredkind' which
432+
*have keys that match at least two of the given attnums. Return NULL if
433+
*there's no match.
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*
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* The current selection criteria is very simple - we choose the statistics
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* referencing the most attributes with the least keys.

‎src/backend/utils/cache/relcache.c

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -4508,7 +4508,6 @@ RelationGetStatExtList(Relation relation)
45084508
NULL,1,&skey);
45094509

45104510
while (HeapTupleIsValid(htup=systable_getnext(indscan)))
4511-
/* TODO maybe include only already built statistics? */
45124511
result=insert_ordered_oid(result,HeapTupleGetOid(htup));
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45144513
systable_endscan(indscan);

‎src/include/nodes/relation.h

Lines changed: 3 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -693,17 +693,15 @@ typedef struct ForeignKeyOptInfo
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* StatisticExtInfo
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*Information about extended statistics for planning/optimization
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*
696-
* This contains information about which columns are covered by the
697-
* statistics (stakeys), which options were requested while adding the
698-
* statistics (*_enabled), and which kinds of statistics were actually
699-
* built and are available for the optimizer (*_built).
696+
* Each pg_statistic_ext row is represented by one or more nodes of this
697+
* type, or even zero if ANALYZE has not computed them.
700698
*/
701699
typedefstructStatisticExtInfo
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{
703701
NodeTagtype;
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705703
OidstatOid;/* OID of the statistics row */
706-
RelOptInfo*rel;/* back-link toindex's table */
704+
RelOptInfo*rel;/* back-link tostatistic's table */
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charkind;/* statistic kind of this entry */
708706
Bitmapset*keys;/* attnums of the columns covered */
709707
}StatisticExtInfo;

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