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Create the pg_pltemplate system catalog to hold template information
for procedural languages. This replaces the hard-wired table I had originally proposed as a stopgap solution. For the moment, the initial contents only include languages shipped with the core distribution.
This commit is contained in:
Tom Lane
@ -1,6 +1,6 @@
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<!--
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Documentation of the system catalogs, directed toward PostgreSQL developers
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$PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.112 2005/08/24 17:24:17 tgl Exp $
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$PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.113 2005/09/08 20:07:41 tgl Exp $
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-->
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<chapter id="catalogs">
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@ -168,6 +168,11 @@
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<entry>operators</entry>
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</row>
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<row>
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<entry><link linkend="catalog-pg-pltemplate"><structname>pg_pltemplate</structname></link></entry>
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<entry>template data for procedural languages</entry>
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</row>
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<row>
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<entry><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link></entry>
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<entry>functions and procedures</entry>
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@ -3027,6 +3032,106 @@
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</sect1>
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<sect1 id="catalog-pg-pltemplate">
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<title><structname>pg_pltemplate</structname></title>
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<indexterm zone="catalog-pg-pltemplate">
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<primary>pg_pltemplate</primary>
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</indexterm>
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<para>
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The catalog <structname>pg_pltemplate</structname> stores
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<quote>template</> information for procedural languages.
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A template for a language allows the language to be created in a
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particular database by a simple <command>CREATE LANGUAGE</> command,
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with no need to specify implementation details.
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</para>
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<para>
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Unlike most system catalogs, <structname>pg_pltemplate</structname>
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is shared across all databases of a cluster: there is only one
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copy of <structname>pg_pltemplate</structname> per cluster, not
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one per database. This allows the information to be accessible in
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each database as it is needed.
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</para>
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<table>
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<title><structname>pg_pltemplate</> Columns</title>
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<tgroup cols=4>
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<thead>
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<row>
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<entry>Name</entry>
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<entry>Type</entry>
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<entry>References</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><structfield>tmplname</structfield></entry>
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<entry><type>name</type></entry>
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<entry></entry>
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<entry>Name of the language this template is for</entry>
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</row>
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<row>
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<entry><structfield>tmpltrusted</structfield></entry>
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<entry><type>boolean</type></entry>
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<entry></entry>
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<entry>True if language is considered trusted</entry>
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</row>
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<row>
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<entry><structfield>tmplhandler</structfield></entry>
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<entry><type>text</type></entry>
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<entry></entry>
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<entry>Name of call handler function</entry>
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</row>
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<row>
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<entry><structfield>tmplvalidator</structfield></entry>
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<entry><type>text</type></entry>
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<entry></entry>
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<entry>Name of validator function, or NULL if none</entry>
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</row>
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<row>
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<entry><structfield>tmpllibrary</structfield></entry>
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<entry><type>text</type></entry>
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<entry></entry>
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<entry>Path of shared library that implements language</entry>
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</row>
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<row>
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<entry><structfield>tmplacl</structfield></entry>
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<entry><type>aclitem[]</type></entry>
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<entry></entry>
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<entry>Access privileges for template (not yet used)</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>
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There are not currently any commands that manipulate procedural language
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templates; to change the built-in information, a superuser must modify
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the table using ordinary INSERT, DELETE, or UPDATE commands. It is
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likely that a future release of <productname>PostgreSQL</productname>
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will offer commands to change the entries in a cleaner fashion.
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</para>
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<para>
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When implemented, the <structfield>tmplacl</structfield> field will provide
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access control for the template itself (i.e., the right to create a
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language using it), not for the languages created from the template.
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</para>
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</sect1>
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<sect1 id="catalog-pg-proc">
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<title><structname>pg_proc</structname></title>
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@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/create_language.sgml,v 1.40 2005/09/05 23:50:48 tgl Exp $
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$PostgreSQL: pgsql/doc/src/sgml/ref/create_language.sgml,v 1.41 2005/09/08 20:07:41 tgl Exp $
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PostgreSQL documentation
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-->
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@ -48,22 +48,19 @@ CREATE [ TRUSTED ] [ PROCEDURAL ] LANGUAGE <replaceable class="parameter">name</
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<para>
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There are two forms of the <command>CREATE LANGUAGE</command> command.
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In the first form, the user merely supplies the name of the desired
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In the first form, the user supplies just the name of the desired
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language, and the <productname>PostgreSQL</productname> server consults
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an internal table to determine the correct parameters. In
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the second form, the user supplies the language parameters along with
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the language name. The second form must be used to create a language
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that is not present in the internal table, but this form is considered
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obsolescent. (It is expected that future releases of
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<productname>PostgreSQL</productname> will replace the internal table
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with a system catalog that can be extended to support additional
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languages.)
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the <link linkend="catalog-pg-pltemplate"><structname>pg_pltemplate</structname></link>
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system catalog to determine the correct parameters. In the second form,
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the user supplies the language parameters along with the language name.
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The second form can be used to create a language that is not defined in
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<structname>pg_pltemplate</>, but this approach is considered obsolescent.
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</para>
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<para>
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When the server finds an entry in its internal table for the given
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language name, it will use the table data even if the given command
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includes language parameters. This behavior simplifies loading of
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When the server finds an entry in the <structname>pg_pltemplate</> catalog
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for the given language name, it will use the catalog data even if the
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command includes language parameters. This behavior simplifies loading of
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old dump files, which are likely to contain out-of-date information
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about language support functions.
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</para>
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@ -165,8 +162,8 @@ CREATE [ TRUSTED ] [ PROCEDURAL ] LANGUAGE <replaceable class="parameter">name</
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<para>
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The <literal>TRUSTED</> option and the support function name(s) are
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ignored if the server has information about the specified language
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name in its internal table.
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ignored if the server has an entry for the specified language
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name in <structname>pg_pltemplate</>.
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</para>
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</refsect1>
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@ -207,9 +204,9 @@ CREATE [ TRUSTED ] [ PROCEDURAL ] LANGUAGE <replaceable class="parameter">name</
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<para>
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The call handler function and the validator function (if any)
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must already exist if the server does not have information about
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the language in its internal table. But when there is an entry
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in the internal table, the functions need not already exist;
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must already exist if the server does not have an entry for the language
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in <structname>pg_pltemplate</>. But when there is an entry,
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the functions need not already exist;
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they will be automatically defined if not present in the database.
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(This can result in <command>CREATE LANGUAGE</> failing, if the
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shared library that implements the language is not available in
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@ -239,8 +236,8 @@ CREATE LANGUAGE plpgsql;
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</para>
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<para>
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For a language not known in the server's internal table, a sequence
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such as this is needed:
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For a language not known in the <structname>pg_pltemplate</> catalog, a
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sequence such as this is needed:
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<programlisting>
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CREATE FUNCTION plsample_call_handler() RETURNS language_handler
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AS '$libdir/plsample'
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@ -1,5 +1,5 @@
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<!--
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$PostgreSQL: pgsql/doc/src/sgml/ref/createlang.sgml,v 1.36 2005/09/05 23:50:48 tgl Exp $
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$PostgreSQL: pgsql/doc/src/sgml/ref/createlang.sgml,v 1.37 2005/09/08 20:07:41 tgl Exp $
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PostgreSQL documentation
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-->
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@ -40,11 +40,9 @@ PostgreSQL documentation
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<para>
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<application>createlang</application> is a utility for adding a new
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programming language to a <productname>PostgreSQL</productname> database.
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<application>createlang</application> can handle all the languages
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supplied in the default <productname>PostgreSQL</> distribution, but
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not languages provided by other parties. See
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<application>createlang</application> is just a wrapper around the
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<xref linkend="sql-createlanguage" endterm="sql-createlanguage-title">
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for additional information.
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command, which see for additional information.
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</para>
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</refsect1>
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