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Commitf409502

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Provide statistics for hypothetical BRIN indexes
Trying to use hypothetical indexes with BRIN currently fails when tryingto access a relation that does not exist when looking for thestatistics. With the current API, it is not possible to easily passa value for pages_per_range down to the hypothetical index, so thismakes use of the default value of BRIN_DEFAULT_PAGES_PER_RANGE, whichshould be fine enough in most cases.Being able to refine or enforce the hypothetical costs in moreoptimistic ways would require more refactoring by filling in thestatistics when building IndexOptInfo in plancat.c. This would involveABI breakages around the costing routines, something not fit for stablebranches.This is broken since7e534ad, so backpatch down to v10.Author: Julien Rouhaud, Heikki LinnakangasReviewed-by: Álvaro Herrera, Tom Lane, Michael PaquierDiscussion:https://postgr.es/m/CAOBaU_ZH0LKEA8VFCocr6Lpte1ab0b6FpvgS0y4way+RPSXfYg@mail.gmail.comBackpatch-through: 10
1 parenta45feb1 commitf409502

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lines changed

‎src/backend/utils/adt/selfuncs.c

Lines changed: 25 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -102,6 +102,7 @@
102102
#include<math.h>
103103

104104
#include"access/brin.h"
105+
#include"access/brin_page.h"
105106
#include"access/gin.h"
106107
#include"access/htup_details.h"
107108
#include"access/sysattr.h"
@@ -7879,11 +7880,31 @@ brincostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
78797880
&spc_seq_page_cost);
78807881

78817882
/*
7882-
* Obtain some data from the index itself.
7883+
* Obtain some data from the index itself, if possible. Otherwise invent
7884+
* some plausible internal statistics based on the relation page count.
78837885
*/
7884-
indexRel=index_open(index->indexoid,AccessShareLock);
7885-
brinGetStats(indexRel,&statsData);
7886-
index_close(indexRel,AccessShareLock);
7886+
if (!index->hypothetical)
7887+
{
7888+
indexRel=index_open(index->indexoid,AccessShareLock);
7889+
brinGetStats(indexRel,&statsData);
7890+
index_close(indexRel,AccessShareLock);
7891+
7892+
/* work out the actual number of ranges in the index */
7893+
indexRanges=Max(ceil((double)baserel->pages /
7894+
statsData.pagesPerRange),1.0);
7895+
}
7896+
else
7897+
{
7898+
/*
7899+
* Assume default number of pages per range, and estimate the number
7900+
* of ranges based on that.
7901+
*/
7902+
indexRanges=Max(ceil((double)baserel->pages /
7903+
BRIN_DEFAULT_PAGES_PER_RANGE),1.0);
7904+
7905+
statsData.pagesPerRange=BRIN_DEFAULT_PAGES_PER_RANGE;
7906+
statsData.revmapNumPages= (indexRanges /REVMAP_PAGE_MAXITEMS)+1;
7907+
}
78877908

78887909
/*
78897910
* Compute index correlation
@@ -7984,10 +8005,6 @@ brincostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
79848005
baserel->relid,
79858006
JOIN_INNER,NULL);
79868007

7987-
/* work out the actual number of ranges in the index */
7988-
indexRanges=Max(ceil((double)baserel->pages /statsData.pagesPerRange),
7989-
1.0);
7990-
79918008
/*
79928009
* Now calculate the minimum possible ranges we could match with if all of
79938010
* the rows were in the perfect order in the table's heap.

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