store more index entries), but at the same time the summary data stored can

be more precise and more data blocks can be skipped during an index scan.

</para>

<sect2 id="brin-operation">

<title>Index Maintenance</title>

<para>

At the time of creation, all existing index pages are scanned and a

summary index tuple is created for each range, including the

possibly-incomplete range at the end.

As new pages are filled with data, page ranges that are already

summarized will cause the summary information to be updated with data

from the new tuples.

When a new page is created that does not fall within the last

summarized range, that range does not automatically acquire a summary

tuple; those tuples remain unsummarized until a summarization run is

invoked later, creating initial summaries.

This process can be invoked manually using the

<function>brin_summarize_new_pages(regclass)</function> function,

or automatically when <command>VACUUM</command> processes the table.

</para>

</sect2>

</sect1>

<sect1 id="brin-builtin-opclasses">

</sect2>

<sect2 id="functions-admin-index">

<title>Index Maintenance Functions</title>

<indexterm>

<primary>brin_summarize_new_values</primary>

</indexterm>

<para>

<xref linkend="functions-admin-index-table"> shows the functions

available for index maintenance tasks.

</para>

<table id="functions-admin-index-table">

<title>Index Maintenance Functions</title>

<tgroup cols="3">

<thead>

<row><entry>Name</entry> <entry>Return Type</entry> <entry>Description</entry></row>

</thead>

<tbody>

<row>

<entry>

<literal><function>brin_summarize_new_values(<parameter>index_oid</> <type>regclass</>)</function></literal>

</entry>

<entry><type>integer</type></entry>

<entry>summarize page ranges not already summarized</entry>

</row>

</tbody>

</tgroup>

</table>

<para>

<function>brin_summarize_new_values</> receives a BRIN index OID as

argument and inspects the index to find page ranges in the base table

that are not currently summarized by the index; for any such range

it creates a new summary index tuple by scanning the table pages.

It returns the number of new page range summaries that were inserted

into the index.

</para>

</sect2>

<sect2 id="functions-admin-genfile">

<title>Generic File Access Functions</title>