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Commit649b5ec

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Add the ability to store inheritance-tree statistics in pg_statistic,
and teach ANALYZE to compute such stats for tables that have subclasses.Per my proposal of yesterday.autovacuum still needs to be taught about running ANALYZE on parent tableswhen their subclasses change, but the feature is useful even without that.
1 parent84d723b commit649b5ec

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18 files changed

+407
-177
lines changed

18 files changed

+407
-177
lines changed

‎doc/src/sgml/catalogs.sgml

Lines changed: 33 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.214 2009/12/17 14:36:15 rhaas Exp $ -->
1+
<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.215 2009/12/29 20:11:42 tgl Exp $ -->
22
<!--
33
Documentation of the system catalogs, directed toward PostgreSQL developers
44
-->
@@ -4506,19 +4506,32 @@
45064506
The catalog <structname>pg_statistic</structname> stores
45074507
statistical data about the contents of the database. Entries are
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created by <xref linkend="sql-analyze" endterm="sql-analyze-title">
4509-
and subsequently used by the query planner. There is one entry for
4510-
each table column that has been analyzed. Note that all the
4509+
and subsequently used by the query planner. Note that all the
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statistical data is inherently approximate, even assuming that it
45124511
is up-to-date.
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</para>
45144513

4514+
<para>
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Normally there is one entry, with <structfield>stainherit</> =
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<literal>false</>, for each table column that has been analyzed.
4517+
If the table has inheritance children, a second entry with
4518+
<structfield>stainherit</> = <literal>true</> is also created. This row
4519+
represents the column's statistics over the inheritance tree, i.e.,
4520+
statistics for the data you'd see with
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<literal>SELECT <replaceable>column</> FROM <replaceable>table</>*</literal>,
4522+
whereas the <structfield>stainherit</> = <literal>false</> row represents
4523+
the results of
4524+
<literal>SELECT <replaceable>column</> FROM ONLY <replaceable>table</></literal>.
4525+
</para>
4526+
45154527
<para>
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<structname>pg_statistic</structname> also stores statistical data about
45174529
the values of index expressions. These are described as if they were
45184530
actual data columns; in particular, <structfield>starelid</structfield>
45194531
references the index. No entry is made for an ordinary non-expression
45204532
index column, however, since it would be redundant with the entry
4521-
for the underlying table column.
4533+
for the underlying table column. Currently, entries for index expressions
4534+
always have <structfield>stainherit</> = <literal>false</>.
45224535
</para>
45234536

45244537
<para>
@@ -4572,6 +4585,14 @@
45724585
<entry>The number of the described column</entry>
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</row>
45744587

4588+
<row>
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<entry><structfield>stainherit</structfield></entry>
4590+
<entry><type>bool</type></entry>
4591+
<entry></entry>
4592+
<entry>If true, the stats include inheritance child columns, not just the
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values in the specified relation</entry>
4594+
</row>
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45754596
<row>
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<entry><structfield>stanullfrac</structfield></entry>
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<entry><type>float4</type></entry>
@@ -7114,6 +7135,14 @@
71147135
<entry>Name of the column described by this row</entry>
71157136
</row>
71167137

7138+
<row>
7139+
<entry><structfield>inherited</structfield></entry>
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<entry><type>bool</type></entry>
7141+
<entry></entry>
7142+
<entry>If true, this row includes inheritance child columns, not just the
7143+
values in the specified table</entry>
7144+
</row>
7145+
71177146
<row>
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<entry><structfield>null_frac</structfield></entry>
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<entry><type>real</type></entry>

‎src/backend/catalog/heap.c

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
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*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/catalog/heap.c,v 1.362 2009/12/24 22:09:23 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/catalog/heap.c,v 1.363 2009/12/29 20:11:43 tgl Exp $
1212
*
1313
*
1414
* INTERFACE ROUTINES
@@ -2314,7 +2314,7 @@ cookConstraint(ParseState *pstate,
23142314
/*
23152315
* RemoveStatistics --- remove entries in pg_statistic for a rel or column
23162316
*
2317-
* If attnum is zero, remove all entries for rel; else remove only the one
2317+
* If attnum is zero, remove all entries for rel; else remove only the one(s)
23182318
* for that column.
23192319
*/
23202320
void
@@ -2344,9 +2344,10 @@ RemoveStatistics(Oid relid, AttrNumber attnum)
23442344
nkeys=2;
23452345
}
23462346

2347-
scan=systable_beginscan(pgstatistic,StatisticRelidAttnumIndexId, true,
2347+
scan=systable_beginscan(pgstatistic,StatisticRelidAttnumInhIndexId, true,
23482348
SnapshotNow,nkeys,key);
23492349

2350+
/* we must loop even when attnum != 0, in case of inherited stats */
23502351
while (HeapTupleIsValid(tuple=systable_getnext(scan)))
23512352
simple_heap_delete(pgstatistic,&tuple->t_self);
23522353

‎src/backend/catalog/system_views.sql

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
*
44
* Copyright (c) 1996-2009, PostgreSQL Global Development Group
55
*
6-
* $PostgreSQL: pgsql/src/backend/catalog/system_views.sql,v 1.63 2009/11/2918:14:30 tgl Exp $
6+
* $PostgreSQL: pgsql/src/backend/catalog/system_views.sql,v 1.64 2009/12/2920:11:44 tgl Exp $
77
*/
88

99
CREATEVIEWpg_rolesAS
@@ -109,6 +109,7 @@ CREATE VIEW pg_stats AS
109109
nspnameAS schemaname,
110110
relnameAS tablename,
111111
attnameAS attname,
112+
stainheritAS inherited,
112113
stanullfracAS null_frac,
113114
stawidthAS avg_width,
114115
stadistinctAS n_distinct,

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