-<!-- $PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.78 2010/02/01 15:48:35 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.79 2010/02/05 18:11:46 momjian Exp $ -->
<chapter id="plperl">
<title>PL/Perl - Perl Procedural Language</title>
<primary>spi_exec_query</primary>
<secondary>in PL/Perl</secondary>
</indexterm>
+ <indexterm>
+ <primary>spi_query</primary>
+ <secondary>in PL/Perl</secondary>
+ </indexterm>
+ <indexterm>
+ <primary>spi_fetchrow</primary>
+ <secondary>in PL/Perl</secondary>
+ </indexterm>
+ <indexterm>
+ <primary>spi_prepare</primary>
+ <secondary>in PL/Perl</secondary>
+ </indexterm>
+ <indexterm>
+ <primary>spi_exec_prepared</primary>
+ <secondary>in PL/Perl</secondary>
+ </indexterm>
+ <indexterm>
+ <primary>spi_query_prepared</primary>
+ <secondary>in PL/Perl</secondary>
+ </indexterm>
+ <indexterm>
+ <primary>spi_cursor_close</primary>
+ <secondary>in PL/Perl</secondary>
+ </indexterm>
+ <indexterm>
+ <primary>spi_freeplan</primary>
+ <secondary>in PL/Perl</secondary>
+ </indexterm>
<term><literal><function>spi_exec_query</>(<replaceable>query</replaceable> [, <replaceable>max-rows</replaceable>])</literal></term>
- <term><literal><function>spi_query</>(<replaceable>command</replaceable>)</literal></term>
- <term><literal><function>spi_fetchrow</>(<replaceable>cursor</replaceable>)</literal></term>
- <term><literal><function>spi_prepare</>(<replaceable>command</replaceable>, <replaceable>argument types</replaceable>)</literal></term>
- <term><literal><function>spi_exec_prepared</>(<replaceable>plan</replaceable>, <replaceable>arguments</replaceable>)</literal></term>
- <term><literal><function>spi_query_prepared</>(<replaceable>plan</replaceable> [, <replaceable>attributes</replaceable>], <replaceable>arguments</replaceable>)</literal></term>
- <term><literal><function>spi_cursor_close</>(<replaceable>cursor</replaceable>)</literal></term>
- <term><literal><function>spi_freeplan</>(<replaceable>plan</replaceable>)</literal></term>
-
<listitem>
<para>
<literal>spi_exec_query</literal> executes an SQL command and
SELECT * FROM test_munge();
</programlisting>
</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><literal><function>spi_query</>(<replaceable>command</replaceable>)</literal></term>
+ <term><literal><function>spi_fetchrow</>(<replaceable>cursor</replaceable>)</literal></term>
+ <term><literal><function>spi_cursor_close</>(<replaceable>cursor</replaceable>)</literal></term>
+
+ <listitem>
<para>
<literal>spi_query</literal> and <literal>spi_fetchrow</literal>
work together as a pair for row sets which might be large, or for cases
</para>
<para>
+ Normally, <function>spi_fetchrow</> should be repeated until it
+ returns <literal>undef</literal>, indicating that there are no more
+ rows to read. The cursor returned by <literal>spi_query</literal>
+ is automatically freed when
+ <function>spi_fetchrow</> returns <literal>undef</literal>.
+ If you do not wish to read all the rows, instead call
+ <function>spi_cursor_close</> to free the cursor.
+ Failure to do so will result in memory leaks.
+ </para>
+
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal><function>spi_prepare</>(<replaceable>command</replaceable>, <replaceable>argument types</replaceable>)</literal></term>
+ <term><literal><function>spi_query_prepared</>(<replaceable>plan</replaceable>, <replaceable>arguments</replaceable>)</literal></term>
+ <term><literal><function>spi_exec_prepared</>(<replaceable>plan</replaceable> [, <replaceable>attributes</replaceable>], <replaceable>arguments</replaceable>)</literal></term>
+ <term><literal><function>spi_freeplan</>(<replaceable>plan</replaceable>)</literal></term>
+
+ <listitem>
+ <para>
<literal>spi_prepare</literal>, <literal>spi_query_prepared</literal>, <literal>spi_exec_prepared</literal>,
- and <literal>spi_freeplan</literal> implement the same functionality but for prepared queries. Once
- a query plan is prepared by a call to <literal>spi_prepare</literal>, the plan can be used instead
+ and <literal>spi_freeplan</literal> implement the same functionality but for prepared queries.
+ <literal>spi_prepare</literal> accepts a query string with numbered argument placeholders ($1, $2, etc)
+ and a string list of argument types:
+<programlisting>
+$plan = spi_prepare('SELECT * FROM test WHERE id > $1 AND name = $2', 'INTEGER', 'TEXT');
+</programlisting>
+ Once a query plan is prepared by a call to <literal>spi_prepare</literal>, the plan can be used instead
of the string query, either in <literal>spi_exec_prepared</literal>, where the result is the same as returned
by <literal>spi_exec_query</literal>, or in <literal>spi_query_prepared</literal> which returns a cursor
exactly as <literal>spi_query</literal> does, which can be later passed to <literal>spi_fetchrow</literal>.
+ The optional second parameter to <literal>spi_exec_prepared</literal> is a hash reference of attributes;
+ the only attribute currently supported is <literal>limit</literal>, which sets the maximum number of rows returned by a query.
</para>
<para>
<para>
<programlisting>
-CREATE OR REPLACE FUNCTION init() RETURNS INTEGER AS $$
+CREATE OR REPLACE FUNCTION init() RETURNS VOID AS $$
$_SHARED{my_plan} = spi_prepare( 'SELECT (now() + $1)::date AS now', 'INTERVAL');
$$ LANGUAGE plperl;
CREATE OR REPLACE FUNCTION add_time( INTERVAL ) RETURNS TEXT AS $$
return spi_exec_prepared(
$_SHARED{my_plan},
- $_[0],
+ $_[0]
)->{rows}->[0]->{now};
$$ LANGUAGE plperl;
-CREATE OR REPLACE FUNCTION done() RETURNS INTEGER AS $$
+CREATE OR REPLACE FUNCTION done() RETURNS VOID AS $$
spi_freeplan( $_SHARED{my_plan});
undef $_SHARED{my_plan};
$$ LANGUAGE plperl;
</para>
<para>
- Normally, <function>spi_fetchrow</> should be repeated until it
- returns <literal>undef</literal>, indicating that there are no more
- rows to read. The cursor is automatically freed when
- <function>spi_fetchrow</> returns <literal>undef</literal>.
- If you do not wish to read all the rows, instead call
- <function>spi_cursor_close</> to free the cursor.
- Failure to do so will result in memory leaks.
+ Another example illustrates usage of an optional parameter in <literal>spi_exec_prepared</literal>:
</para>
- </listitem>
+
+ <para>
+ <programlisting>
+CREATE TABLE hosts AS SELECT id, ('192.168.1.'||id)::inet AS address FROM generate_series(1,3) AS id;
+
+CREATE OR REPLACE FUNCTION init_hosts_query() RETURNS VOID AS $$
+ $_SHARED{plan} = spi_prepare('SELECT * FROM hosts WHERE address << $1', 'inet');
+$$ LANGUAGE plperl;
+
+CREATE OR REPLACE FUNCTION query_hosts(inet) RETURNS SETOF hosts AS $$
+ return spi_exec_prepared(
+ $_SHARED{plan},
+ {limit => 2},
+ $_[0]
+ )->{rows};
+$$ LANGUAGE plperl;
+
+CREATE OR REPLACE FUNCTION release_hosts_query() RETURNS VOID AS $$
+ spi_freeplan($_SHARED{plan});
+ undef $_SHARED{plan};
+$$ LANGUAGE plperl;
+
+SELECT init_hosts_query();
+SELECT query_hosts('192.168.1.0/30');
+SELECT release_hosts_query();
+
+ query_hosts
+-----------------
+ (1,192.168.1.1)
+ (2,192.168.1.2)
+(2 rows)
+ </programlisting>
+ </para>
+ </listitem>
</varlistentry>
</variablelist>
</sect2>