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Doc: improve docs about pg_statistic_ext_data.

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Commit aa087ec64 was a bit over-hasty about the doc changes needed
while splitting pg_statistic_ext_data off from pg_statistic_ext.
It duplicated one para and inserted another in what seems to me
to be the wrong section.  Fix that up, and in passing do some minor
copy-editing.

Per report from noborusai.

Discussion: https://postgr.es/m/CAAM3qnLXLUz4mOBkqa8jxigpKhKNxzSuvwpjvCRPvO5EqWjxSg@mail.gmail.com
This commit is contained in:
Tom Lane 2019-10-06 14:14:45 -04:00
parent ac12ab06a9
commit 732457b5d2
1 changed files with 21 additions and 27 deletions
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48
doc/src/sgml/catalogs.sgml
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@ -6376,28 +6376,6 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
about those tables that are readable by the current user.
</para>
<para>
<structname>pg_statistic</structname> should not be readable by the
public, since even statistical information about a table's contents
might be considered sensitive. (Example: minimum and maximum values
of a salary column might be quite interesting.)
<link linkend="view-pg-stats"><structname>pg_stats</structname></link>
is a publicly readable view on
<structname>pg_statistic</structname> that only exposes information
about those tables that are readable by the current user.
</para>
<para>
Similarly, <structname>pg_statistic_ext_data</structname> should not be
readable by the public, since the contents might be considered sensitive.
(Example: most common combination of values in columns might be quite
interesting.)
<link linkend="view-pg-stats-ext"><structname>pg_stats_ext</structname></link>
is a publicly readable view on <structname>pg_statistic_ext_data</structname>
(after joining with <structname>pg_statistic_ext</structname>) that only exposes
information about those tables and columns that are readable by the current user.
</para>
<table>
<title><structname>pg_statistic</structname> Columns</title>
@ -6616,9 +6594,11 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
</table>
<para>
The <structfield>stxkind</structfield> field is filled at creation of the
statistics object, indicating which statistic type(s) are desired. The
statistics (once computed by <command>ANALYZE</command>) are stored in
The <structname>pg_statistic_ext</structname> entry is filled in
completely during <command>CREATE STATISTICS</command>, but the actual
statistical values are not computed then.
Subsequent <command>ANALYZE</command> commands compute the desired values
and populate an entry in the
<link linkend="catalog-pg-statistic-ext-data"><structname>pg_statistic_ext_data</structname></link>
catalog.
</para>
@ -6638,6 +6618,20 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
created with <xref linkend="sql-createstatistics"/>.
</para>
<para>
Like <structname>pg_statistic</structname>,
<structname>pg_statistic_ext_data</structname> should not be
readable by the public, since the contents might be considered sensitive.
(Example: most common combinations of values in columns might be quite
interesting.)
<link linkend="view-pg-stats-ext"><structname>pg_stats_ext</structname></link>
is a publicly readable view
on <structname>pg_statistic_ext_data</structname> (after joining
with <structname>pg_statistic_ext</structname>) that only exposes
information about those tables and columns that are readable by the
current user.
</para>
<table>
<title><structname>pg_statistic_ext_data</structname> Columns</title>
@ -6657,7 +6651,7 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
<entry><structfield>stxoid</structfield></entry>
<entry><type>oid</type></entry>
<entry><literal><link linkend="catalog-pg-statistic-ext"><structname>pg_statistic_ext</structname></link>.oid</literal></entry>
<entry>Extended statistic containing the definition for this data.</entry>
<entry>Extended statistic object containing the definition for this data</entry>
</row>
<row>
@ -6685,7 +6679,7 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
<entry></entry>
<entry>
MCV (most-common values) list statistics, serialized as
<structname>pg_mcv_list</structname> type.
<structname>pg_mcv_list</structname> type
</entry>
</row>