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Postgres FD Implementation
Commit 5d723d05 authored by Andrew Dunstan's avatar Andrew Dunstan
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Prepared queries for PLPerl, plus fixing a small plperl memory leak. Patch
and docs from Dmitry Karasik, slightly editorialised.
parent f2f5b056
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doc/src/sgml/plperl.sgml
View file @ 5d723d05
<!--
$PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.50 2006/03/01 06:30:32 neilc Exp $
$PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.51 2006/03/05 16:40:51 adunstan Exp $
-->
<chapter id="plperl">
......@@ -296,7 +296,7 @@ BEGIN { strict->import(); }
</para>
<para>
PL/Perl provides three additional Perl commands:
PL/Perl provides additional Perl commands:
<variablelist>
<varlistentry>
......@@ -306,9 +306,13 @@ BEGIN { strict->import(); }
</indexterm>
<term><literal><function>spi_exec_query</>(<replaceable>query</replaceable> [, <replaceable>max-rows</replaceable>])</literal></term>
<term><literal><function>spi_exec_query</>(<replaceable>command</replaceable>)</literal></term>
<term><literal><function>spi_query</>(<replaceable>command</replaceable>)</literal></term>
<term><literal><function>spi_fetchrow</>(<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>)</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>
......@@ -420,6 +424,66 @@ SELECT * from lotsa_md5(500);
</programlisting>
</para>
<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
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>.
</para>
<para>
The advantage of prepared queries is that is it possible to use one prepared plan for more
than one query execution. After the plan is not needed anymore, it must be freed with
<literal>spi_freeplan</literal>:
</para>
<para>
<programlisting>
CREATE OR REPLACE FUNCTION init() RETURNS INTEGER 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 $$
return spi_exec_prepared(
$_SHARED{my_plan},
$_[0],
)->{rows}->[0]->{now};
$$ LANGUAGE plperl;
CREATE OR REPLACE FUNCTION done() RETURNS INTEGER AS $$
spi_freeplan( $_SHARED{my_plan});
undef $_SHARED{my_plan};
$$ LANGUAGE plperl;
SELECT init();
SELECT add_time('1 day'), add_time('2 days'), add_time('3 days');
SELECT done();
add_time | add_time | add_time
------------+------------+------------
2005-12-10 | 2005-12-11 | 2005-12-12
</programlisting>
</para>
<para>
Note that the parameter subscript in <literal>spi_prepare</literal> is defined via
$1, $2, $3, etc, so avoid declaring query strings in double quotes that might easily
lead to hard-to-catch bugs.
</para>
<para>
<literal>spi_cursor_close</literal> can be used to abort sequence of
<literal>spi_fetchrow</literal> calls. Normally, the call to
<literal>spi_fetchrow</literal> that returns <literal>undef</literal> is
the signal that there are no more rows to read. Also
that call automatically frees the cursor associated with the query. If it is desired not
to read all retuned rows, <literal>spi_cursor_close</literal> must be
called to avoid memory leaks.
</para>
</listitem>
</varlistentry>
......
src/pl/plperl/SPI.xs
View file @ 5d723d05
......@@ -111,7 +111,8 @@ spi_spi_exec_query(query, ...)
int limit = 0;
CODE:
if (items > 2)
croak("Usage: spi_exec_query(query, limit) or spi_exec_query(query)");
croak("Usage: spi_exec_query(query, limit) "
"or spi_exec_query(query)");
if (items == 2)
limit = SvIV(ST(1));
ret_hash = plperl_spi_exec(query, limit);
......@@ -141,5 +142,84 @@ spi_spi_fetchrow(cursor)
OUTPUT:
RETVAL
SV*
spi_spi_prepare(query, ...)
char* query;
CODE:
int i;
SV** argv;
if (items < 1)
Perl_croak(aTHX_ "Usage: spi_prepare(query, ...)");
argv = ( SV**) palloc(( items - 1) * sizeof(SV*));
if ( argv == NULL)
Perl_croak(aTHX_ "spi_prepare: not enough memory");
for ( i = 1; i < items; i++)
argv[i - 1] = ST(i);
RETVAL = plperl_spi_prepare(query, items - 1, argv);
pfree( argv);
OUTPUT:
RETVAL
SV*
spi_spi_exec_prepared(query, ...)
char * query;
PREINIT:
HV *ret_hash;
CODE:
HV *attr = NULL;
int i, offset = 1, argc;
SV ** argv;
if ( items < 1)
Perl_croak(aTHX_ "Usage: spi_exec_prepared(query, [\\%%attr,] "
"[\\@bind_values])");
if ( items > 1 && SvROK( ST( 1)) && SvTYPE( SvRV( ST( 1))) == SVt_PVHV)
{
attr = ( HV*) SvRV(ST(1));
offset++;
}
argc = items - offset;
argv = ( SV**) palloc( argc * sizeof(SV*));
if ( argv == NULL)
Perl_croak(aTHX_ "spi_exec_prepared: not enough memory");
for ( i = 0; offset < items; offset++, i++)
argv[i] = ST(offset);
ret_hash = plperl_spi_exec_prepared(query, attr, argc, argv);
RETVAL = newRV_noinc((SV*)ret_hash);
pfree( argv);
OUTPUT:
RETVAL
SV*
spi_spi_query_prepared(query, ...)
char * query;
CODE:
int i;
SV ** argv;
if ( items < 1)
Perl_croak(aTHX_ "Usage: spi_query_prepared(query, "
"[\\@bind_values])");
argv = ( SV**) palloc(( items - 1) * sizeof(SV*));
if ( argv == NULL)
Perl_croak(aTHX_ "spi_query_prepared: not enough memory");
for ( i = 1; i < items; i++)
argv[i - 1] = ST(i);
RETVAL = plperl_spi_query_prepared(query, items - 1, argv);
pfree( argv);
OUTPUT:
RETVAL
void
spi_spi_freeplan(query)
char *query;
CODE:
plperl_spi_freeplan(query);
void
spi_spi_cursor_close(cursor)
char *cursor;
CODE:
plperl_spi_cursor_close(cursor);
BOOT:
items = 0; /* avoid 'unused variable' warning */
src/pl/plperl/expected/plperl.out
View file @ 5d723d05
......@@ -367,6 +367,20 @@ SELECT * from perl_spi_func();
2
(2 rows)
--
-- Test spi_fetchrow abort
--
CREATE OR REPLACE FUNCTION perl_spi_func2() RETURNS INTEGER AS $$
my $x = spi_query("select 1 as a union select 2 as a");
spi_cursor_close( $x);
return 0;
$$ LANGUAGE plperl;
SELECT * from perl_spi_func2();
perl_spi_func2
----------------
0
(1 row)
---
--- Test recursion via SPI
---
......@@ -420,3 +434,37 @@ SELECT array_of_text();
{{"a\"b",NULL,"c,d"},{"e\\f",NULL,g}}
(1 row)
--
-- Test spi_prepare/spi_exec_prepared/spi_freeplan
--
CREATE OR REPLACE FUNCTION perl_spi_prepared(INTEGER) RETURNS INTEGER AS $$
my $x = spi_prepare('select $1 AS a', 'INT4');
my $q = spi_exec_prepared( $x, $_[0] + 1);
spi_freeplan($x);
return $q->{rows}->[0]->{a};
$$ LANGUAGE plperl;
SELECT * from perl_spi_prepared(42);
perl_spi_prepared
-------------------
43
(1 row)
--
-- Test spi_prepare/spi_query_prepared/spi_freeplan
--
CREATE OR REPLACE FUNCTION perl_spi_prepared_set(INTEGER, INTEGER) RETURNS SETOF INTEGER AS $$
my $x = spi_prepare('SELECT $1 AS a union select $2 as a', 'INT4', 'INT4');
my $q = spi_query_prepared( $x, 1+$_[0], 2+$_[1]);
while (defined (my $y = spi_fetchrow($q))) {
return_next $y->{a};
}
spi_freeplan($x);
return;
$$ LANGUAGE plperl;
SELECT * from perl_spi_prepared_set(1,2);
perl_spi_prepared_set
-----------------------
2
4
(2 rows)
src/pl/plperl/plperl.c
View file @ 5d723d05
This diff is collapsed.
src/pl/plperl/plperl.h
View file @ 5d723d05
......@@ -8,7 +8,7 @@
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1995, Regents of the University of California
*
* $PostgreSQL: pgsql/src/pl/plperl/plperl.h,v 1.3 2006/03/05 15:59:10 momjian Exp $
* $PostgreSQL: pgsql/src/pl/plperl/plperl.h,v 1.4 2006/03/05 16:40:51 adunstan Exp $
*/
#ifndef PL_PERL_H
......@@ -51,6 +51,12 @@ HV *plperl_spi_exec(char *, int);
void plperl_return_next(SV *);
SV *plperl_spi_query(char *);
SV *plperl_spi_fetchrow(char *);
SV *plperl_spi_prepare(char *, int, SV **);
HV *plperl_spi_exec_prepared(char *, HV *, int, SV **);
SV *plperl_spi_query_prepared(char *, int, SV **);
void plperl_spi_freeplan(char *);
void plperl_spi_cursor_close(char *);
#endif /* PL_PERL_H */
src/pl/plperl/sql/plperl.sql
View file @ 5d723d05
......@@ -261,6 +261,16 @@ return;
$$ LANGUAGE plperl;
SELECT * from perl_spi_func();
--
-- Test spi_fetchrow abort
--
CREATE OR REPLACE FUNCTION perl_spi_func2() RETURNS INTEGER AS $$
my $x = spi_query("select 1 as a union select 2 as a");
spi_cursor_close( $x);
return 0;
$$ LANGUAGE plperl;
SELECT * from perl_spi_func2();
---
--- Test recursion via SPI
......@@ -301,3 +311,29 @@ LANGUAGE plperl as $$
$$;
SELECT array_of_text();
--
-- Test spi_prepare/spi_exec_prepared/spi_freeplan
--
CREATE OR REPLACE FUNCTION perl_spi_prepared(INTEGER) RETURNS INTEGER AS $$
my $x = spi_prepare('select $1 AS a', 'INT4');
my $q = spi_exec_prepared( $x, $_[0] + 1);
spi_freeplan($x);
return $q->{rows}->[0]->{a};
$$ LANGUAGE plperl;
SELECT * from perl_spi_prepared(42);
--
-- Test spi_prepare/spi_query_prepared/spi_freeplan
--
CREATE OR REPLACE FUNCTION perl_spi_prepared_set(INTEGER, INTEGER) RETURNS SETOF INTEGER AS $$
my $x = spi_prepare('SELECT $1 AS a union select $2 as a', 'INT4', 'INT4');
my $q = spi_query_prepared( $x, 1+$_[0], 2+$_[1]);
while (defined (my $y = spi_fetchrow($q))) {
return_next $y->{a};
}
spi_freeplan($x);
return;
$$ LANGUAGE plperl;
SELECT * from perl_spi_prepared_set(1,2);
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