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Implement function-local GUC parameter settings, as per recent discussion.

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There are still some loose ends: I didn't do anything about the SET FROM
CURRENT idea yet, and it's not real clear whether we are happy with the
interaction of SET LOCAL with function-local settings.  The documentation
is a bit spartan, too.
This commit is contained in:
Tom Lane
2007-09-03 00:39:26 +00:00
parent fcfe801ab8
commit 2abae34a2e
23 changed files with 2583 additions and 2151 deletions
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43
doc/src/sgml/ref/alter_function.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/alter_function.sgml,v 1.13 2007/01/22 01:35:19 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/alter_function.sgml,v 1.14 2007/09/03 00:39:12 tgl Exp $
PostgreSQL documentation
-->
@ -36,6 +36,8 @@ where <replaceable class="PARAMETER">action</replaceable> is one of:
[ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER
COST <replaceable class="parameter">execution_cost</replaceable>
ROWS <replaceable class="parameter">result_rows</replaceable>
SET <replaceable class="parameter">parameter</replaceable> { TO | = } { <replaceable class="parameter">value</replaceable> | DEFAULT }
RESET <replaceable class="parameter">parameter</replaceable>
</synopsis>
</refsynopsisdiv>
@ -212,6 +214,28 @@ where <replaceable class="PARAMETER">action</replaceable> is one of:
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable>parameter</replaceable></term>
<term><replaceable>value</replaceable></term>
<listitem>
<para>
Add or change the assignment to be made to a configuration parameter
when the function is called. If
<replaceable>value</replaceable> is <literal>DEFAULT</literal>
or, equivalently, <literal>RESET</literal> is used, the function-local
setting is removed, so that the function executes with the value
present in its environment. Use <literal>RESET
ALL</literal> to clear all function-local settings.
</para>
<para>
See <xref linkend="sql-set" endterm="sql-set-title"> and
<xref linkend="runtime-config">
for more information about allowed parameter names and values.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>RESTRICT</literal></term>
@ -250,6 +274,22 @@ ALTER FUNCTION sqrt(integer) OWNER TO joe;
ALTER FUNCTION sqrt(integer) SET SCHEMA maths;
</programlisting>
</para>
<para>
To adjust the search path that is automatically set for a function:
<programlisting>
ALTER FUNCTION check_password(text) SET search_path = admin, pg_temp;
</programlisting>
</para>
<para>
To disable automatic setting of <varname>search_path</> for a function:
<programlisting>
ALTER FUNCTION check_password(text) RESET search_path;
</programlisting>
The function will now execute with whatever search path is used by its
caller.
</para>
</refsect1>
<refsect1>
@ -260,6 +300,7 @@ ALTER FUNCTION sqrt(integer) SET SCHEMA maths;
FUNCTION</> statement in the SQL standard. The standard allows more
properties of a function to be modified, but does not provide the
ability to rename a function, make a function a security definer,
attach configuration parameter values to a function,
or change the owner, schema, or volatility of a function. The standard also
requires the <literal>RESTRICT</> key word, which is optional in
<productname>PostgreSQL</>.

82
doc/src/sgml/ref/create_function.sgml
View File

@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.75 2007/04/23 16:52:53 neilc Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.76 2007/09/03 00:39:13 tgl Exp $
-->
<refentry id="SQL-CREATEFUNCTION">
@ -28,6 +28,7 @@ CREATE [ OR REPLACE ] FUNCTION
| [ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER
| COST <replaceable class="parameter">execution_cost</replaceable>
| ROWS <replaceable class="parameter">result_rows</replaceable>
| SET <replaceable class="parameter">parameter</replaceable> { TO | = } { <replaceable class="parameter">value</replaceable> | DEFAULT }
| AS '<replaceable class="parameter">definition</replaceable>'
| AS '<replaceable class="parameter">obj_file</replaceable>', '<replaceable class="parameter">link_symbol</replaceable>'
} ...
@ -71,6 +72,8 @@ CREATE [ OR REPLACE ] FUNCTION
triggers, etc. that refer to the old function. Use
<command>CREATE OR REPLACE FUNCTION</command> to change a function
definition without breaking objects that refer to the function.
Also, <command>ALTER FUNCTION</> can be used to change most of the
auxiliary properties of an existing function.
</para>
<para>
@ -320,6 +323,24 @@ CREATE [ OR REPLACE ] FUNCTION
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable>parameter</replaceable></term>
<term><replaceable>value</replaceable></term>
<listitem>
<para>
The <literal>SET</> clause causes the specified configuration
parameter to be set to the specified value when the function is
entered, and then restored to its prior value when the function exits.
</para>
<para>
See <xref linkend="sql-set" endterm="sql-set-title"> and
<xref linkend="runtime-config">
for more information about allowed parameter names and values.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">definition</replaceable></term>
@ -451,6 +472,18 @@ CREATE FUNCTION foo(int, out text) ...
be escaped by doubling them.
</para>
<para>
If any <literal>SET</> clauses are attached to a function, then
the effects of a <command>SET LOCAL</> command executed inside the
function are restricted to the function: the configuration parameter's
value is restored at function exit. This is true even for parameters
not mentioned in the <literal>SET</> clause(s). However, an ordinary
<command>SET</> command (without <literal>LOCAL</>) overrides the
<literal>SET</> clause, much as it would do for a previous <command>SET
LOCAL</> command: the effects of such a command will persist after
function exit, unless the current transaction is rolled back.
</para>
<para>
To be able to define a function, the user must have the
<literal>USAGE</literal> privilege on the language.
@ -530,28 +563,45 @@ SELECT * FROM dup(42);
CREATE FUNCTION check_password(uname TEXT, pass TEXT)
RETURNS BOOLEAN AS $$
DECLARE passed BOOLEAN;
old_path TEXT;
BEGIN
-- Save old search_path; notice we must qualify current_setting
-- to ensure we invoke the right function
old_path := pg_catalog.current_setting('search_path');
-- Set a secure search_path: trusted schemas, then 'pg_temp'.
-- We set is_local = true so that the old value will be restored
-- in event of an error before we reach the function end.
PERFORM pg_catalog.set_config('search_path', 'admin, pg_temp', true);
-- Do whatever secure work we came for.
SELECT (pwd = $2) INTO passed
FROM pwds
WHERE username = $1;
-- Restore caller's search_path
PERFORM pg_catalog.set_config('search_path', old_path, true);
RETURN passed;
END;
$$ LANGUAGE plpgsql SECURITY DEFINER;
$$ LANGUAGE plpgsql
SECURITY DEFINER
-- Set a secure search_path: trusted schema(s), then 'pg_temp'.
SET search_path = admin, pg_temp;
</programlisting>
<para>
Before <productname>PostgreSQL</productname> version 8.3, the
<literal>SET</> option was not available, and so older functions may
contain rather complicated logic to save, set, and restore
<varname>search_path</>. The <literal>SET</> option is far easier
to use for this purpose.
</para>
<para>
Another point to keep in mind is that by default, execute privilege
is granted to <literal>PUBLIC</> for newly created functions
(see <xref linkend="sql-grant" endterm="sql-grant-title"> for more
information). Frequently you will wish to restrict use of a security
definer function to only some users. To do that, you must revoke
the default <literal>PUBLIC</> privileges and then grant execute
privilege selectively. To avoid having a window where the new function
is accessible to all, create it and set the privileges within a single
transaction. For example:
</para>
<programlisting>
BEGIN;
CREATE FUNCTION check_password(uname TEXT, pass TEXT) ... SECURITY DEFINER;
REVOKE ALL ON FUNCTION check_password(uname TEXT, pass TEXT) FROM PUBLIC;
GRANT EXECUTE ON FUNCTION check_password(uname TEXT, pass TEXT) TO admins;
COMMIT;
</programlisting>
</refsect1>