Add information about range type stats to pg_stats_ext_exprs

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

diff --git a/doc/src/sgml/system-views.sgml b/doc/src/sgml/system-views.sgml
index 8b4abef8c681ece5e2d218f8ca91b9a2daaf0fac..e5fe423fc61036ec910967e6c71d799e8a281703 100644 (file)
--- a/doc/src/sgml/system-views.sgml
+++ b/doc/src/sgml/system-views.sgml
@@ -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>

diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 7553f31fef06cdb9d19f7b9325b4cb5d89febbe4..1ea8f1faa9e6cc6a64f8adf17969c0779e891135 100644 (file)
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -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)

diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index a09d8a6c645bbf5892d169d9b6b67e05d55cc82e..a910b3d04e63c84a4d6c5bcbb1abb7b81ed018a0 100644 (file)
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -57,6 +57,6 @@
  */
 
 /*                                                     yyyymmddN */
-#define CATALOG_VERSION_NO     202602051
+#define CATALOG_VERSION_NO     202602101
 
 #endif

diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index f4ee2bd7459e63c3df46f9aad50d6b0cadaa7886..f9bc213e5a106bc523a73248ea9eaba02454eb9a 100644 (file)
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -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)))

diff --git a/src/test/regress/expected/stats_ext.out b/src/test/regress/expected/stats_ext.out
index b2a065791355bf7b44ddac6a02afed4b538a22f6..cb8856ac50fccb6e57fcb9a8174c5b57bada9fd3 100644 (file)
--- a/src/test/regress/expected/stats_ext.out
+++ b/src/test/regress/expected/stats_ext.out
@@ -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;

diff --git a/src/test/regress/sql/stats_ext.sql b/src/test/regress/sql/stats_ext.sql
index 76ee9d29c0881cfd213dee5355c6cd6309760539..9dcce3440c866e453ace2a36d4f808dbfac14fbe 100644 (file)
--- a/src/test/regress/sql/stats_ext.sql
+++ b/src/test/regress/sql/stats_ext.sql
@@ -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;