<!--
-$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.64 2005/04/05 18:05:45 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.65 2005/04/07 14:53:04 tgl Exp $
-->
<chapter id="plpgsql">
<para>
Because <application>PL/pgSQL</application> saves execution plans
- in this way, SQL commands that appear directly in a
-
<application>PL/pgSQL</application> function must refer to the
- same tables and columns on every execution; that is, you cannot use
- a parameter as the name of a table or column in an SQL command. To get
- around this restriction, you can construct dynamic commands using
-
the <application>PL/pgSQL</application> <command>EXECUTE</command>
- statement — at the price of constructing a new execution plan on
- every execution.
+ in this way, SQL commands that appear directly in a
+ <application>PL/pgSQL</application> function must refer to the
+ same tables and columns on every execution; that is, you cannot use
+ a parameter as the name of a table or column in an SQL command. To get
+ around this restriction, you can construct dynamic commands using
+ the <application>PL/pgSQL</application> <command>EXECUTE</command>
+ statement — at the price of constructing a new execution plan on
+ every execution.
</para>
<note>
CREATE FUNCTION sales_tax(subtotal real, OUT tax real) AS $$
BEGIN
tax := subtotal * 0.06;
- RETURN;
END;
$$ LANGUAGE plpgsql;
</programlisting>
BEGIN
sum := x + y;
prod := x * y;
- RETURN;
END;
$$ LANGUAGE plpgsql;
</programlisting>
AS $$
BEGIN
sum := v1 + v2 + v3;
- RETURN;
END;
$$ LANGUAGE plpgsql;
</programlisting>
</para>
<para>
- The return value of a function cannot be left undefined. If
- control reaches the end of the top-level block of the function
- without hitting a <command>RETURN</command> statement, a run-time
- error will occur.
+ If you declared the function to return <type>void</type>, a
+ <command>RETURN</command> statement can be used to exit the function
+ early; but do not write an expression following
+ <command>RETURN</command>.
</para>
<para>
- If you have declared the function to
- return <type>void</type>, a <command>RETURN</command> statement
- must still be provided; but in this case the expression following
- <command>RETURN</command> is optional and will be ignored if present.
+ The return value of a function cannot be left undefined. If
+ control reaches the end of the top-level block of the function
+ without hitting a <command>RETURN</command> statement, a run-time
+ error will occur. This restriction does not apply to functions
+ with output parameters and functions returning <type>void</type>,
+ however. In those cases a <command>RETURN</command> statement is
+ automatically executed if the top-level block finishes.
</para>
</sect3>
the <application>PL/pgSQL</> function. As successive
<command>RETURN NEXT</command> commands are executed, the result
set is built up. A final <command>RETURN</command>, which should
- have no argument, causes control to exit the function.
+ have no argument, causes control to exit the function (or you can
+ just let control reach the end of the function).
</para>
<para>
RETURN NEXT $1;
OPEN $2 FOR SELECT * FROM table_2;
RETURN NEXT $2;
- RETURN;
END;
$$ LANGUAGE plpgsql;
<listitem>
<para>
- In <productname>PostgreSQL</> you need to use dollar quoting or escape
+ In <productname>PostgreSQL</> the function body has to be written as
+ a string literal. Therefore you need to use dollar quoting or escape
single quotes in the function body. See <xref
linkend="plpgsql-quote-tips">.
</para>
<para>
Here is an <productname>Oracle</productname> <application>PL/SQL</> function:
<programlisting>
-CREATE OR REPLACE FUNCTION cs_fmt_browser_version(v_name IN varchar,
- v_version IN varchar)
+CREATE OR REPLACE FUNCTION cs_fmt_browser_version(v_name varchar,
+ v_version varchar)
RETURN varchar IS
BEGIN
IF v_version IS NULL THEN
</para>
<para>
- Let's go through this function and see the differences to <application>PL/pgSQL</>:
+ Let's go through this function and see the differences compared to
+ <application>PL/pgSQL</>:
<itemizedlist>
<listitem>
<para>
- <productname>Oracle</productname> can have
- <literal>IN</literal>, <literal>OUT</literal>, and
- <literal>INOUT</literal> parameters passed to functions.
- <literal>INOUT</literal>, for example, means that the
- parameter will receive a value and return
- another. <productname>PostgreSQL</> only has <literal>IN</literal>
- parameters, and hence there is no specification of the parameter kind.
- </para>
- </listitem>
-
- <listitem>
- <para>
The <literal>RETURN</literal> key word in the function
prototype (not the function body) becomes
<literal>RETURNS</literal> in
|| ' LANGUAGE plpgsql;' ;
EXECUTE func_cmd;
- RETURN;
END;
$func$ LANGUAGE plpgsql;
</programlisting>
<para>
<xref linkend="plpgsql-porting-ex3"> shows how to port a function
with <literal>OUT</> parameters and string manipulation.
- <productname>PostgreSQL</> does not have an
- <function>instr</function> function, but you can work around it
+ <productname>PostgreSQL</> does not have a built-in
+ <function>instr</function> function, but you can create one
using a combination of other
functions.<indexterm><primary>instr</></indexterm> In <xref
linkend="plpgsql-porting-appendix"> there is a
<para>
The following <productname>Oracle</productname> PL/SQL procedure is used
to parse a URL and return several elements (host, path, and query).
- In <productname>PostgreSQL</>, functions can return only one value.
- One way to work around this is to make the return value a composite
- type (row type).
</para>
<para>
<para>
Here is a possible translation into <application>PL/pgSQL</>:
<programlisting>
-CREATE TYPE cs_parse_url_result AS (
- v_host VARCHAR,
- v_path VARCHAR,
- v_query VARCHAR
-);
-
-CREATE OR REPLACE FUNCTION cs_parse_url(v_url VARCHAR)
-RETURNS cs_parse_url_result AS $$
+CREATE OR REPLACE FUNCTION cs_parse_url(
+ v_url IN VARCHAR,
+ v_host OUT VARCHAR, -- This will be passed back
+ v_path OUT VARCHAR, -- This one too
+ v_query OUT VARCHAR) -- And this one
+AS $$
DECLARE
- res cs_parse_url_result;
a_pos1 INTEGER;
a_pos2 INTEGER;
BEGIN
- res.v_host := NULL;
- res.v_path := NULL;
- res.v_query := NULL;
+ v_host := NULL;
+ v_path := NULL;
+ v_query := NULL;
a_pos1 := instr(v_url, '//');
IF a_pos1 = 0 THEN
- RETURN res;
+ RETURN;
END IF;
a_pos2 := instr(v_url, '/', a_pos1 + 2);
IF a_pos2 = 0 THEN
- res.v_host := substr(v_url, a_pos1 + 2);
- res.v_path := '/';
- RETURN res;
+ v_host := substr(v_url, a_pos1 + 2);
+ v_path := '/';
+ RETURN;
END IF;
- res.v_host := substr(v_url, a_pos1 + 2, a_pos2 - a_pos1 - 2);
+ v_host := substr(v_url, a_pos1 + 2, a_pos2 - a_pos1 - 2);
a_pos1 := instr(v_url, '?', a_pos2 + 1);
IF a_pos1 = 0 THEN
- res.v_path := substr(v_url, a_pos2);
- RETURN res;
+ v_path := substr(v_url, a_pos2);
+ RETURN;
END IF;
- res.v_path := substr(v_url, a_pos2, a_pos1 - a_pos2);
- res.v_query := substr(v_url, a_pos1 + 1);
- RETURN res;
+ v_path := substr(v_url, a_pos2, a_pos1 - a_pos2);
+ v_query := substr(v_url, a_pos1 + 1);
END;
$$ LANGUAGE plpgsql;
</programlisting>
WHEN unique_violation THEN <co id="co.plpgsql-porting-exception">
-- don't worry if it already exists
END;
-
- RETURN;
END;
$$ LANGUAGE plpgsql;
</programlisting>
* procedural language
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_comp.c,v 1.86 2005/04/05 06:22:16 tgl Exp $
+ * $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_comp.c,v 1.87 2005/04/07 14:53:04 tgl Exp $
*
* This software is copyrighted by Jan Wieck - Hamburg.
*
int parse_rc;
Oid rettypeid;
int numargs;
- int num_in_args;
- int num_out_args;
+ int num_in_args = 0;
+ int num_out_args = 0;
Oid *argtypes;
char **argnames;
char *argmodes;
/*
* Create the variables for the procedure's parameters.
*/
- num_in_args = num_out_args = 0;
for (i = 0; i < numargs; i++)
{
char buf[32];
parse_rc = plpgsql_yyparse();
if (parse_rc != 0)
elog(ERROR, "plpgsql parser returned %d", parse_rc);
+ function->action = plpgsql_yylval.program;
plpgsql_scanner_finish();
pfree(proc_source);
/*
- * If that was successful, complete the function's info.
+ * If it has OUT parameters or returns VOID or returns a set, we allow
+ * control to fall off the end without an explicit RETURN statement.
+ * The easiest way to implement this is to add a RETURN statement to the
+ * end of the statement list during parsing. However, if the outer block
+ * has an EXCEPTION clause, we need to make a new outer block, since the
+ * added RETURN shouldn't act like it is inside the EXCEPTION clause.
+ */
+ if (num_out_args > 0 || function->fn_rettype == VOIDOID ||
+ function->fn_retset)
+ {
+ if (function->action->exceptions != NIL)
+ {
+ PLpgSQL_stmt_block *new;
+
+ new = palloc0(sizeof(PLpgSQL_stmt_block));
+ new->cmd_type = PLPGSQL_STMT_BLOCK;
+ new->body = list_make1(function->action);
+
+ function->action = new;
+ }
+ if (function->action->body == NIL ||
+ ((PLpgSQL_stmt *) llast(function->action->body))->cmd_type != PLPGSQL_STMT_RETURN)
+ {
+ PLpgSQL_stmt_return *new;
+
+ new = palloc0(sizeof(PLpgSQL_stmt_return));
+ new->cmd_type = PLPGSQL_STMT_RETURN;
+ new->expr = NULL;
+ new->retvarno = function->out_param_varno;
+
+ function->action->body = lappend(function->action->body, new);
+ }
+ }
+
+ /*
+ * Complete the function's info
*/
function->fn_nargs = procStruct->pronargs;
for (i = 0; i < function->fn_nargs; i++)
function->datums = palloc(sizeof(PLpgSQL_datum *) * plpgsql_nDatums);
for (i = 0; i < plpgsql_nDatums; i++)
function->datums[i] = plpgsql_Datums[i];
- function->action = plpgsql_yylval.program;
/* Debug dump for completed functions */
if (plpgsql_DumpExecTree)
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