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The endterm attribute is mainly useful when the toolchain does not support automatic link target text generation for a particular situation. In the past, this was required by the man page tools for all reference page links, but that is no longer the case, and it now actually gets in the way of proper automatic link text generation. The only remaining use cases are currently xrefs to refsects.
172 lines
4.5 KiB
Plaintext
172 lines
4.5 KiB
Plaintext
<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/create_conversion.sgml,v 1.23 2010/04/03 07:22:58 petere Exp $ -->
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<refentry id="SQL-CREATECONVERSION">
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<refmeta>
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<refentrytitle>CREATE CONVERSION</refentrytitle>
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<manvolnum>7</manvolnum>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>CREATE CONVERSION</refname>
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<refpurpose>define a new encoding conversion</refpurpose>
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</refnamediv>
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<indexterm zone="sql-createconversion">
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<primary>CREATE CONVERSION</primary>
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</indexterm>
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<refsynopsisdiv>
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<synopsis>
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CREATE [ DEFAULT ] CONVERSION <replaceable>name</replaceable>
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FOR <replaceable>source_encoding</replaceable> TO <replaceable>dest_encoding</replaceable> FROM <replaceable>function_name</replaceable>
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</synopsis>
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</refsynopsisdiv>
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<refsect1 id="sql-createconversion-description">
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<title>Description</title>
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<para>
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<command>CREATE CONVERSION</command> defines a new conversion between
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character set encodings. Also, conversions that
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are marked <literal>DEFAULT</> can be used for automatic encoding
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conversion between
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client and server. For this purpose, two conversions, from encoding A to
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B <emphasis>and</emphasis> from encoding B to A, must be defined.
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</para>
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<para>
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To be able to create a conversion, you must have <literal>EXECUTE</literal> privilege
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on the function and <literal>CREATE</literal> privilege on the destination schema.
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</para>
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</refsect1>
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<refsect1>
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<title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><literal>DEFAULT</literal></term>
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<listitem>
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<para>
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The <literal>DEFAULT</> clause indicates that this conversion
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is the default for this particular source to destination
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encoding. There should be only one default encoding in a schema
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for the encoding pair.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable>name</replaceable></term>
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<listitem>
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<para>
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The name of the conversion. The conversion name can be
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schema-qualified. If it is not, the conversion is defined in the
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current schema. The conversion name must be unique within a
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schema.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable>source_encoding</replaceable></term>
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<listitem>
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<para>
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The source encoding name.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable>dest_encoding</replaceable></term>
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<listitem>
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<para>
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The destination encoding name.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable>function_name</replaceable></term>
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<listitem>
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<para>
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The function used to perform the conversion. The function name can
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be schema-qualified. If it is not, the function will be looked
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up in the path.
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</para>
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<para>
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The function must have the following signature:
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<programlisting>
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conv_proc(
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integer, -- source encoding ID
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integer, -- destination encoding ID
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cstring, -- source string (null terminated C string)
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internal, -- destination (fill with a null terminated C string)
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integer -- source string length
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) RETURNS void;
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</programlisting>
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id="sql-createconversion-notes">
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<title>Notes</title>
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<para>
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Use <command>DROP CONVERSION</command> to remove user-defined conversions.
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</para>
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<para>
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The privileges required to create a conversion might be changed in a future
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release.
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</para>
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</refsect1>
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<refsect1 id="sql-createconversion-examples">
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<title>Examples</title>
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<para>
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To create a conversion from encoding <literal>UTF8</literal> to
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<literal>LATIN1</literal> using <function>myfunc</>:
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<programlisting>
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CREATE CONVERSION myconv FOR 'UTF8' TO 'LATIN1' FROM myfunc;
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</programlisting>
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</para>
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</refsect1>
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<refsect1 id="sql-createconversion-compat">
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<title>Compatibility</title>
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<para>
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<command>CREATE CONVERSION</command>
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is a <productname>PostgreSQL</productname> extension.
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There is no <command>CREATE CONVERSION</command>
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statement in the SQL standard.
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</para>
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</refsect1>
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<refsect1 id="sql-createconversion-seealso">
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<title>See Also</title>
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<simplelist type="inline">
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<member><xref linkend="sql-alterconversion"></member>
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<member><xref linkend="sql-createfunction"></member>
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<member><xref linkend="sql-dropconversion"></member>
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</simplelist>
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</refsect1>
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</refentry>
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