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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Indexes and Collations</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.2.24 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Indexes" HREF="indexes.html"><LINK REL="PREVIOUS" TITLE="Operator Classes and Operator Families" HREF="indexes-opclass.html"><LINK REL="NEXT" TITLE="Examining Index Usage" HREF="indexes-examine.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2017-11-06T22:43:11"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.2.24 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="Operator Classes and Operator Families" HREF="indexes-opclass.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="indexes.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 11. Indexes</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="Examining Index Usage" HREF="indexes-examine.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="INDEXES-COLLATIONS" >11.10. Indexes and Collations</A ></H1 ><P > An index can support only one collation per index column. If multiple collations are of interest, multiple indexes may be needed. </P ><P > Consider these statements: </P><PRE CLASS="PROGRAMLISTING" >CREATE TABLE test1c ( id integer, content varchar COLLATE "x" ); CREATE INDEX test1c_content_index ON test1c (content);</PRE ><P> The index automatically uses the collation of the underlying column. So a query of the form </P><PRE CLASS="PROGRAMLISTING" >SELECT * FROM test1c WHERE content > <TT CLASS="REPLACEABLE" ><I >constant</I ></TT >;</PRE ><P> could use the index, because the comparison will by default use the collation of the column. However, this index cannot accelerate queries that involve some other collation. So if queries of the form, say, </P><PRE CLASS="PROGRAMLISTING" >SELECT * FROM test1c WHERE content > <TT CLASS="REPLACEABLE" ><I >constant</I ></TT > COLLATE "y";</PRE ><P> are also of interest, an additional index could be created that supports the <TT CLASS="LITERAL" >"y"</TT > collation, like this: </P><PRE CLASS="PROGRAMLISTING" >CREATE INDEX test1c_content_y_index ON test1c (content COLLATE "y");</PRE ><P> </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="indexes-opclass.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="indexes-examine.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Operator Classes and Operator Families</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="indexes.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Examining Index Usage</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
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