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Commit14ef15a

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Don't build extended statistics on inheritance trees
When performing ANALYZE on inheritance trees, we collect two samples foreach relation - one for the relation alone, and one for the inheritancesubtree (relation and its child relations). And then we build statisticson each sample, so for each relation we get two sets of statistics.For regular (per-column) statistics this works fine, because the catalogincludes a flag differentiating statistics built from those two samples.But we don't have such flag in the extended statistics catalogs, and weended up updating the same row twice, triggering this error: ERROR: tuple already updated by selfThe simplest solution is to disable extended statistics on inheritancetrees, which is what this commit is doing. In the future we may need todo something similar to per-column statistics, but that requires adding aflag to the catalog - and that's not backpatchable. Moreover, the currentselectivity estimation code only works with individual relations, sobuilding statistics on inheritance trees would be pointless anyway.Author: Tomas VondraBackpatch-to: 10-Discussion:https://postgr.es/m/20190618231233.GA27470@telsasoft.comReported-by: Justin Pryzby
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3 files changed

+25
-3
lines changed

3 files changed

+25
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lines changed

‎src/backend/commands/analyze.c

Lines changed: 9 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -574,9 +574,15 @@ do_analyze_rel(Relation onerel, VacuumParams *params,
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thisdata->attr_cnt,thisdata->vacattrstats);
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}
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/* Build extended statistics (if there are any). */
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BuildRelationExtStatistics(onerel,totalrows,numrows,rows,attr_cnt,
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vacattrstats);
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/*
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* Build extended statistics (if there are any).
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*
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* For now we only build extended statistics on individual relations,
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* not for relations representing inheritance trees.
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*/
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if (!inh)
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BuildRelationExtStatistics(onerel,totalrows,numrows,rows,
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attr_cnt,vacattrstats);
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}
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/*

‎src/test/regress/expected/stats_ext.out

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -103,6 +103,14 @@ ANALYZE ab1 (a);
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WARNING: statistics object "public.ab1_a_b_stats" could not be computed for relation "public.ab1"
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ANALYZE ab1;
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DROP TABLE ab1;
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-- Ensure we can build statistics for tables with inheritance.
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CREATE TABLE ab1 (a INTEGER, b INTEGER);
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CREATE TABLE ab1c () INHERITS (ab1);
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INSERT INTO ab1 VALUES (1,1);
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CREATE STATISTICS ab1_a_b_stats ON a, b FROM ab1;
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ANALYZE ab1;
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DROP TABLE ab1 CASCADE;
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NOTICE: drop cascades to table ab1c
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-- Verify supported object types for extended statistics
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CREATE schema tststats;
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CREATE TABLE tststats.t (a int, b int, c text);

‎src/test/regress/sql/stats_ext.sql

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Original file line numberDiff line numberDiff line change
@@ -73,6 +73,14 @@ ANALYZE ab1 (a);
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ANALYZE ab1;
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DROPTABLE ab1;
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-- Ensure we can build statistics for tables with inheritance.
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CREATETABLEab1 (aINTEGER, bINTEGER);
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CREATETABLEab1c () INHERITS (ab1);
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INSERT INTO ab1VALUES (1,1);
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CREATE STATISTICS ab1_a_b_statsON a, bFROM ab1;
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ANALYZE ab1;
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DROPTABLE ab1 CASCADE;
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-- Verify supported object types for extended statistics
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CREATEschematststats;
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