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Build inherited extended stats on partitioned tables

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Commit 859b3003de disabled building of extended stats for inheritance
trees, to prevent updating the same catalog row twice. While that
resolved the issue, it also means there are no extended stats for
declaratively partitioned tables, because there are no data in the
non-leaf relations.

That also means declaratively partitioned tables were not affected by
the issue 859b3003de addressed, which means this is a regression
affecting queries that calculate estimates for the whole inheritance
tree as a whole (which includes e.g. GROUP BY queries).

But because partitioned tables are empty, we can invert the condition
and build statistics only for the case with inheritance, without losing
anything. And we can consider them when calculating estimates.

It may be necessary to run ANALYZE on partitioned tables, to collect
proper statistics. For declarative partitioning there should no prior
statistics, and it might take time before autoanalyze is triggered. For
tables partitioned by inheritance the statistics may include data from
child relations (if built 859b3003de), contradicting the current code.

Report and patch by Justin Pryzby, minor fixes and cleanup by me.
Backpatch all the way back to PostgreSQL 10, where extended statistics
were introduced (same as 859b3003de).

Author: Justin Pryzby
Reported-by: Justin Pryzby
Backpatch-through: 10
Discussion: https://postgr.es/m/20210923212624.GI831%40telsasoft.com
This commit is contained in:
Tomas Vondra
2022-01-15 18:17:20 +01:00
parent 2cc007fd03
commit ea212bd95f
6 changed files with 77 additions and 19 deletions
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19
src/test/regress/expected/stats_ext.out
View File

@@ -217,6 +217,25 @@ SELECT * FROM check_estimated_rows('SELECT a, b FROM stxdinh* WHERE a = 0 AND b
(1 row)
DROP TABLE stxdinh, stxdinh1, stxdinh2;
-- Ensure inherited stats ARE applied to inherited query in partitioned table
CREATE TABLE stxdinp(i int, a int, b int) PARTITION BY RANGE (i);
CREATE TABLE stxdinp1 PARTITION OF stxdinp FOR VALUES FROM (1) TO (100);
INSERT INTO stxdinp SELECT 1, a/100, a/100 FROM generate_series(1, 999) a;
CREATE STATISTICS stxdinp ON a, b FROM stxdinp;
VACUUM ANALYZE stxdinp; -- partitions are processed recursively
SELECT 1 FROM pg_statistic_ext WHERE stxrelid = 'stxdinp'::regclass;
?column?
----------
1
(1 row)
SELECT * FROM check_estimated_rows('SELECT a, b FROM stxdinp GROUP BY 1, 2');
estimated | actual
-----------+--------
10 | 10
(1 row)
DROP TABLE stxdinp;
-- basic test for statistics on expressions
CREATE TABLE ab1 (a INTEGER, b INTEGER, c TIMESTAMP, d TIMESTAMPTZ);
-- expression stats may be built on a single expression column

10
src/test/regress/sql/stats_ext.sql
View File

@@ -134,6 +134,16 @@ SELECT * FROM check_estimated_rows('SELECT a, b FROM stxdinh* GROUP BY 1, 2');
SELECT * FROM check_estimated_rows('SELECT a, b FROM stxdinh* WHERE a = 0 AND b = 0');
DROP TABLE stxdinh, stxdinh1, stxdinh2;
-- Ensure inherited stats ARE applied to inherited query in partitioned table
CREATE TABLE stxdinp(i int, a int, b int) PARTITION BY RANGE (i);
CREATE TABLE stxdinp1 PARTITION OF stxdinp FOR VALUES FROM (1) TO (100);
INSERT INTO stxdinp SELECT 1, a/100, a/100 FROM generate_series(1, 999) a;
CREATE STATISTICS stxdinp ON a, b FROM stxdinp;
VACUUM ANALYZE stxdinp; -- partitions are processed recursively
SELECT 1 FROM pg_statistic_ext WHERE stxrelid = 'stxdinp'::regclass;
SELECT * FROM check_estimated_rows('SELECT a, b FROM stxdinp GROUP BY 1, 2');
DROP TABLE stxdinp;
-- basic test for statistics on expressions
CREATE TABLE ab1 (a INTEGER, b INTEGER, c TIMESTAMP, d TIMESTAMPTZ);