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Doc: Correct description of amcheck example query.

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The amcheck documentation incorrectly claimed that its example query
verifies every catalog index in the database.  In fact, the query only
verifies the 10 largest indexes (as determined by pg_class.relpages).
Adjust the description accordingly.

Backpatch: 10-, where contrib/amcheck was introduced.
This commit is contained in:
Peter Geoghegan 2018-08-08 12:56:23 -07:00
parent 79f17d45e8
commit 393e539c54
1 changed files with 9 additions and 11 deletions
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20
doc/src/sgml/amcheck.sgml
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@ -35,7 +35,7 @@
functions.
</para>
<para>
<filename>amcheck</filename> functions may be used only by superusers.
<filename>amcheck</filename> functions may only be used by superusers.
</para>
<sect2>
@ -83,14 +83,13 @@ ORDER BY c.relpages DESC LIMIT 10;
| pg_amop_fam_strat_index | 5
(10 rows)
</screen>
This example shows a session that performs verification of every
catalog index in the database <quote>test</quote>. Details of just
the 10 largest indexes verified are displayed. Verification of
the presence of heap tuples as index tuples is requested for
unique indexes only. Since no error is raised, all indexes
tested appear to be logically consistent. Naturally, this query
could easily be changed to call
<function>bt_index_check</function> for every index in the
This example shows a session that performs verification of the
10 largest catalog indexes in the database <quote>test</quote>.
Verification of the presence of heap tuples as index tuples is
requested for the subset that are unique indexes. Since no
error is raised, all indexes tested appear to be logically
consistent. Naturally, this query could easily be changed to
call <function>bt_index_check</function> for every index in the
database where verification is supported.
</para>
<para>
@ -292,8 +291,7 @@ ORDER BY c.relpages DESC LIMIT 10;
</listitem>
<listitem>
<para>
Corruption caused by faulty RAM, and the broader memory subsystem
and operating system.
Corruption caused by faulty RAM, or the broader memory subsystem.
</para>
<para>
<productname>PostgreSQL</productname> does not protect against correctable