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Add information about range type stats to pg_stats_ext_exprs

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This commit adds three attributes to the system view pg_stats_ext_exprs,
whose data can exist when involving a range type in an expression:
range_length_histogram
range_empty_frac
range_bounds_histogram

These statistics fields exist since 918eee0c497c, and have become
viewable in pg_stats later in bc3c8db8ae2f.  This puts the definition of
pg_stats_ext_exprs on par with pg_stats.

This issue has showed up during the discussion about the restore of
extended statistics for expressions, so as it becomes possible to query
the stats data to restore from the catalogs.  Having access to this data
is useful on its own, without the restore part.

Some documentation and some tests are added, written by me.  Corey has
authored the part in system_views.sql.

Bump catalog version.

Author: Corey Huinker <corey.huinker@gmail.com>
Co-authored-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/aYmCUx9VvrKiZQLL@paquier.xyz
This commit is contained in:
Michael Paquier
2026-02-10 12:36:57 +09:00
parent f41ab51573
commit 307447e6db
6 changed files with 132 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

39
doc/src/sgml/system-views.sgml
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@ -5045,6 +5045,45 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
non-null elements. (Null for scalar types.)
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>range_length_histogram</structfield> <type>anyarray</type>
</para>
<para>
A histogram of the lengths of non-empty and non-null range values of an
expression. (Null for non-range types.)
</para>
<para>
This histogram is calculated using the <function>subtype_diff</function>
range function regardless of whether range bounds are inclusive.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>range_empty_frac</structfield> <type>float4</type>
</para>
<para>
Fraction of expression entries whose values are empty ranges.
(Null for non-range types.)
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>range_bounds_histogram</structfield> <type>anyarray</type>
</para>
<para>
A histogram of lower and upper bounds of non-empty and non-null range
values. (Null for non-range types.)
</para>
<para>
These two histograms are represented as a single array of ranges, whose
lower bounds represent the histogram of lower bounds, and upper bounds
represent the histogram of upper bounds.
</para></entry>
</row>
</tbody>
</tgroup>
</table>

23
src/backend/catalog/system_views.sql
View File

@ -363,7 +363,28 @@ CREATE VIEW pg_stats_ext_exprs WITH (security_barrier) AS
WHEN (stat.a).stakind3 = 5 THEN (stat.a).stanumbers3
WHEN (stat.a).stakind4 = 5 THEN (stat.a).stanumbers4
WHEN (stat.a).stakind5 = 5 THEN (stat.a).stanumbers5
END) AS elem_count_histogram
END) AS elem_count_histogram,
(CASE
WHEN (stat.a).stakind1 = 6 THEN (stat.a).stavalues1
WHEN (stat.a).stakind2 = 6 THEN (stat.a).stavalues2
WHEN (stat.a).stakind3 = 6 THEN (stat.a).stavalues3
WHEN (stat.a).stakind4 = 6 THEN (stat.a).stavalues4
WHEN (stat.a).stakind5 = 6 THEN (stat.a).stavalues5
END) AS range_length_histogram,
(CASE
WHEN (stat.a).stakind1 = 6 THEN (stat.a).stanumbers1[1]
WHEN (stat.a).stakind2 = 6 THEN (stat.a).stanumbers2[1]
WHEN (stat.a).stakind3 = 6 THEN (stat.a).stanumbers3[1]
WHEN (stat.a).stakind4 = 6 THEN (stat.a).stanumbers4[1]
WHEN (stat.a).stakind5 = 6 THEN (stat.a).stanumbers5[1]
END) AS range_empty_frac,
(CASE
WHEN (stat.a).stakind1 = 7 THEN (stat.a).stavalues1
WHEN (stat.a).stakind2 = 7 THEN (stat.a).stavalues2
WHEN (stat.a).stakind3 = 7 THEN (stat.a).stavalues3
WHEN (stat.a).stakind4 = 7 THEN (stat.a).stavalues4
WHEN (stat.a).stakind5 = 7 THEN (stat.a).stavalues5
END) AS range_bounds_histogram
FROM pg_statistic_ext s JOIN pg_class c ON (c.oid = s.stxrelid)
LEFT JOIN pg_statistic_ext_data sd ON (s.oid = sd.stxoid)
LEFT JOIN pg_namespace cn ON (cn.oid = c.relnamespace)

2
src/include/catalog/catversion.h
View File

@ -57,6 +57,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 202602051
#define CATALOG_VERSION_NO 202602101
#endif

26
src/test/regress/expected/rules.out
View File

@ -2696,7 +2696,31 @@ pg_stats_ext_exprs| SELECT cn.nspname AS schemaname,
WHEN ((stat.a).stakind4 = 5) THEN (stat.a).stanumbers4
WHEN ((stat.a).stakind5 = 5) THEN (stat.a).stanumbers5
ELSE NULL::real[]
END AS elem_count_histogram
END AS elem_count_histogram,
CASE
WHEN ((stat.a).stakind1 = 6) THEN (stat.a).stavalues1
WHEN ((stat.a).stakind2 = 6) THEN (stat.a).stavalues2
WHEN ((stat.a).stakind3 = 6) THEN (stat.a).stavalues3
WHEN ((stat.a).stakind4 = 6) THEN (stat.a).stavalues4
WHEN ((stat.a).stakind5 = 6) THEN (stat.a).stavalues5
ELSE NULL::anyarray
END AS range_length_histogram,
CASE
WHEN ((stat.a).stakind1 = 6) THEN (stat.a).stanumbers1[1]
WHEN ((stat.a).stakind2 = 6) THEN (stat.a).stanumbers2[1]
WHEN ((stat.a).stakind3 = 6) THEN (stat.a).stanumbers3[1]
WHEN ((stat.a).stakind4 = 6) THEN (stat.a).stanumbers4[1]
WHEN ((stat.a).stakind5 = 6) THEN (stat.a).stanumbers5[1]
ELSE NULL::real
END AS range_empty_frac,
CASE
WHEN ((stat.a).stakind1 = 7) THEN (stat.a).stavalues1
WHEN ((stat.a).stakind2 = 7) THEN (stat.a).stavalues2
WHEN ((stat.a).stakind3 = 7) THEN (stat.a).stavalues3
WHEN ((stat.a).stakind4 = 7) THEN (stat.a).stavalues4
WHEN ((stat.a).stakind5 = 7) THEN (stat.a).stavalues5
ELSE NULL::anyarray
END AS range_bounds_histogram
FROM (((((pg_statistic_ext s
JOIN pg_class c ON ((c.oid = s.stxrelid)))
LEFT JOIN pg_statistic_ext_data sd ON ((s.oid = sd.stxoid)))

27
src/test/regress/expected/stats_ext.out
View File

@ -3628,3 +3628,30 @@ SELECT * FROM check_estimated_rows('SELECT * FROM sb_2 WHERE numeric_lt(y, 1.0)'
-- Tidy up
DROP TABLE sb_1, sb_2 CASCADE;
-- Check statistics generated for range type and expressions.
CREATE TABLE stats_ext_tbl_range(name text, irange int4range);
INSERT INTO stats_ext_tbl_range VALUES
('red', '[1,7)'::int4range),
('blue', '[2,8]'::int4range),
('green', '[3,9)'::int4range);
CREATE STATISTICS stats_ext_range (mcv)
ON irange, (irange + '[4,10)'::int4range)
FROM stats_ext_tbl_range;
ANALYZE stats_ext_tbl_range;
SELECT attnames, most_common_vals
FROM pg_stats_ext
WHERE statistics_name = 'stats_ext_range';
attnames | most_common_vals
----------+------------------------------------------------------------
{irange} | {{"[1,7)","[1,10)"},{"[2,9)","[2,10)"},{"[3,9)","[3,10)"}}
(1 row)
SELECT range_length_histogram, range_empty_frac, range_bounds_histogram
FROM pg_stats_ext_exprs
WHERE statistics_name = 'stats_ext_range';
range_length_histogram | range_empty_frac | range_bounds_histogram
------------------------+------------------+------------------------------
{7,8,9} | 0 | {"[1,10)","[2,10)","[3,10)"}
(1 row)
DROP TABLE stats_ext_tbl_range;

18
src/test/regress/sql/stats_ext.sql
View File

@ -1866,3 +1866,21 @@ SELECT * FROM check_estimated_rows('SELECT * FROM sb_2 WHERE numeric_lt(y, 1.0)'
-- Tidy up
DROP TABLE sb_1, sb_2 CASCADE;
-- Check statistics generated for range type and expressions.
CREATE TABLE stats_ext_tbl_range(name text, irange int4range);
INSERT INTO stats_ext_tbl_range VALUES
('red', '[1,7)'::int4range),
('blue', '[2,8]'::int4range),
('green', '[3,9)'::int4range);
CREATE STATISTICS stats_ext_range (mcv)
ON irange, (irange + '[4,10)'::int4range)
FROM stats_ext_tbl_range;
ANALYZE stats_ext_tbl_range;
SELECT attnames, most_common_vals
FROM pg_stats_ext
WHERE statistics_name = 'stats_ext_range';
SELECT range_length_histogram, range_empty_frac, range_bounds_histogram
FROM pg_stats_ext_exprs
WHERE statistics_name = 'stats_ext_range';
DROP TABLE stats_ext_tbl_range;