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Improve documentation of pageinspect 

This adds a section for heap-related functions.  These were previously
mixed with functions having a more general purpose, leading to
confusion.  While on it, add a query example for fsm_page_contents.

Backpatch down to 10, where b5e3942 introduced the subsections for
function types in pageinspect documentation.

Author: Masahiko Sawada
Discussion: https://postgr.es/m/CAD21AoDyM7E1+cK3-aWejxKTGC-wVVP2B+RnJhN6inXyeRmqzw@mail.gmail.com
Backpatch-through: 10
This commit is contained in:
Michael Paquier 2019-08-23 20:41:18 +09:00
parent 9d35bc5931
commit 6472d7ad5d
1 changed files with 33 additions and 23 deletions
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56
doc/src/sgml/pageinspect.sgml
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@ -125,6 +125,39 @@ test=# SELECT page_checksum(get_raw_page('pg_class', 0), 0);
</listitem>
</varlistentry>
<varlistentry>
<term>
<function>fsm_page_contents(page bytea) returns text</function>
<indexterm>
<primary>fsm_page_contents</primary>
</indexterm>
</term>
<listitem>
<para>
<function>fsm_page_contents</function> shows the internal node structure
of a FSM page. For example:
<screen>
test=# SELECT fsm_page_contents(get_raw_page('pg_class', 'fsm', 0));
</screen>
The output is a multiline string, with one line per node in the binary
tree within the page. Only those nodes that are not zero are printed.
The so-called "next" pointer, which points to the next slot to be
returned from the page, is also printed.
</para>
<para>
See <filename>src/backend/storage/freespace/README</filename> for more
information on the structure of an FSM page.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>
<sect2>
<title>Heap Functions</title>
<variablelist>
<varlistentry>
<term>
<function>heap_page_items(page bytea) returns setof record</function>
@ -203,29 +236,6 @@ test=# SELECT * FROM heap_page_item_attrs(get_raw_page('pg_class', 0), 'pg_class
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<function>fsm_page_contents(page bytea) returns text</function>
<indexterm>
<primary>fsm_page_contents</primary>
</indexterm>
</term>
<listitem>
<para>
<function>fsm_page_contents</function> shows the internal node structure
of a FSM page. The output is a multiline string, with one line per
node in the binary tree within the page. Only those nodes that are not
zero are printed. The so-called "next" pointer, which points to the
next slot to be returned from the page, is also printed.
</para>
<para>
See <filename>src/backend/storage/freespace/README</filename> for more
information on the structure of an FSM page.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>