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BRIN de-summarization

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When the BRIN summary tuple for a page range becomes too "wide" for the
values actually stored in the table (because the tuples that were
present originally are no longer present due to updates or deletes), it
can be useful to remove the outdated summary tuple, so that a future
summarization can install a tighter summary.

This commit introduces a SQL-callable interface to do so.

Author: Álvaro Herrera
Reviewed-by: Eiji Seki
Discussion: https://postgr.es/m/20170228045643.n2ri74ara4fhhfxf@alvherre.pgsql
This commit is contained in:
Alvaro Herrera
2017-04-01 16:10:04 -03:00
parent 3a82129a40
commit c655899ba9
12 changed files with 340 additions and 5 deletions
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4
doc/src/sgml/brin.sgml
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@ -80,6 +80,10 @@
or by automatic summarization executed by autovacuum, as insertions
occur. (This last trigger is disabled by default and can be enabled
with the <literal>autosummarize</literal> parameter.)
Conversely, a range can be de-summarized using the
<function>brin_desummarize_range(regclass, bigint)</function> range,
which is useful when the index tuple is no longer a very good
representation because the existing values have changed.
</para>
</sect2>

15
doc/src/sgml/func.sgml
View File

@ -19660,6 +19660,14 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
<primary>gin_clean_pending_list</primary>
</indexterm>
<indexterm>
<primary>brin_summarize_range</primary>
</indexterm>
<indexterm>
<primary>brin_desummarize_range</primary>
</indexterm>
<para>
<xref linkend="functions-admin-index-table"> shows the functions
available for index maintenance tasks.
@ -19690,6 +19698,13 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
<entry><type>integer</type></entry>
<entry>summarize the page range covering the given block, if not already summarized</entry>
</row>
<row>
<entry>
<literal><function>brin_desummarize_range(<parameter>index</> <type>regclass</>, <parameter>blockNumber</> <type>bigint</type>)</function></literal>
</entry>
<entry><type>integer</type></entry>
<entry>de-summarize the page range covering the given block, if summarized</entry>
</row>
<row>
<entry>
<literal><function>gin_clean_pending_list(<parameter>index</> <type>regclass</>)</function></literal>