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e56bce5d43
Commit 2453ea142 redefined pg_proc.proargtypes to include the types of
OUT parameters, for procedures only. While that had some advantages
for implementing the SQL-spec behavior of DROP PROCEDURE, it was pretty
disastrous from a number of other perspectives. Notably, since the
primary key of pg_proc is name + proargtypes, this made it possible to
have multiple procedures with identical names + input arguments and
differing output argument types. That would make it impossible to call
any one of the procedures by writing just NULL (or "?", or any other
data-type-free notation) for the output argument(s). The change also
seems likely to cause grave confusion for client applications that
examine pg_proc and expect the traditional definition of proargtypes.
Hence, revert the definition of proargtypes to what it was, and
undo a number of complications that had been added to support that.
To support the SQL-spec behavior of DROP PROCEDURE, when there are
no argmode markers in the command's parameter list, we perform the
lookup both ways (that is, matching against both proargtypes and
proallargtypes), succeeding if we get just one unique match.
In principle this could result in ambiguous-function failures
that would not happen when using only one of the two rules.
However, overloading of procedure names is thought to be a pretty
rare usage, so this shouldn't cause many problems in practice.
Postgres-specific code such as pg_dump can defend against any
possibility of such failures by being careful to specify argmodes
for all procedure arguments.
This also fixes a few other bugs in the area of CALL statements
with named parameters, and improves the documentation a little.
catversion bump forced because the representation of procedures
with OUT arguments changes.
Discussion: https://postgr.es/m/3742981.1621533210@sss.pgh.pa.us
134 lines
3.5 KiB
Plaintext
134 lines
3.5 KiB
Plaintext
<!--
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doc/src/sgml/ref/call.sgml
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PostgreSQL documentation
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-->
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<refentry id="sql-call">
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<indexterm zone="sql-call">
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<primary>CALL</primary>
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</indexterm>
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<refmeta>
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<refentrytitle>CALL</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>CALL</refname>
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<refpurpose>invoke a procedure</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<synopsis>
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CALL <replaceable class="parameter">name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> ] [, ...] )
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</synopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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<command>CALL</command> executes a procedure.
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</para>
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<para>
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If the procedure has any output parameters, then a result row will be
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returned, containing the values of those parameters.
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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><replaceable class="parameter">name</replaceable></term>
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<listitem>
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<para>
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The name (optionally schema-qualified) of the procedure.
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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 class="parameter">argument</replaceable></term>
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<listitem>
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<para>
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An argument expression for the procedure call.
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</para>
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<para>
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Arguments can include parameter names, using the syntax
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<literal><replaceable class="parameter">name</replaceable> => <replaceable class="parameter">value</replaceable></literal>.
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This works the same as in ordinary function calls; see
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<xref linkend="sql-syntax-calling-funcs"/> for details.
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</para>
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<para>
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Arguments must be supplied for all procedure parameters that lack
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defaults, including <literal>OUT</literal> parameters. However,
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arguments matching <literal>OUT</literal> parameters are not evaluated,
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so it's customary to just write <literal>NULL</literal> for them.
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(Writing something else for an <literal>OUT</literal> parameter
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might cause compatibility problems with
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future <productname>PostgreSQL</productname> versions.)
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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>
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<title>Notes</title>
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<para>
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The user must have <literal>EXECUTE</literal> privilege on the procedure in
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order to be allowed to invoke it.
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</para>
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<para>
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To call a function (not a procedure), use <command>SELECT</command> instead.
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</para>
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<para>
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If <command>CALL</command> is executed in a transaction block, then the
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called procedure cannot execute transaction control statements.
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Transaction control statements are only allowed if <command>CALL</command>
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is executed in its own transaction.
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</para>
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<para>
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<application>PL/pgSQL</application> handles output parameters
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in <command>CALL</command> commands differently;
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see <xref linkend="plpgsql-statements-calling-procedure"/>.
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</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<programlisting>
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CALL do_db_maintenance();
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</programlisting>
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</refsect1>
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<refsect1>
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<title>Compatibility</title>
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<para>
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<command>CALL</command> conforms to the SQL standard,
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except for the handling of output parameters. The standard
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says that users should write variables to receive the values
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of output parameters.
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</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<simplelist type="inline">
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<member><xref linkend="sql-createprocedure"/></member>
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</simplelist>
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</refsect1>
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</refentry>
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