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<!entity info SYSTEM "info.sgml">

<!entity catalogs SYSTEM "catalogs.sgml">

<!entity geqo SYSTEM "geqo.sgml">

<!entity gist SYSTEM "gist.sgml">

<!entity gin SYSTEM "gin.sgml">

<!entity planstats SYSTEM "planstats.sgml">

<!entity indexam SYSTEM "indexam.sgml">

<!entity nls SYSTEM "nls.sgml">

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<sect1 id="xindex">

<title>Interfacing Extensions To Indexes</title>

</tgroup>

</table>

<para>

GIN indexes require four support functions,

shown in <xref linkend="xindex-gin-support-table">.

</para>

<table tocentry="1" id="xindex-gin-support-table">

<title>GIN Support Functions</title>

<tgroup cols="2">

<thead>

<row>

<entry>Function</entry>

<entry>Support Number</entry>

</row>

</thead>

<tbody>

<row>

<entry>compare</entry>

<entry>1</entry>

</row>

<row>

<entry>extract value</entry>

<entry>2</entry>

</row>

<row>

<entry>extract query</entry>

<entry>3</entry>

</row>

<row>

<entry>consistent</entry>

<entry>4</entry>

</row>

</tbody>

</tgroup>

</table>

<para>

Unlike strategy operators, support functions return whichever data

type the particular index method expects; for example in the case