Thread: plpqsql and RETURN NEXT requires a LOOP?

plpqsql and RETURN NEXT requires a LOOP?

From

"Davidson, Robert"

Date:

21 March 2006, 16:51:15

<p align="LEFT"><span lang="en-us"><font face="Arial" size="2">From my reading of</font></span><span
lang="en-us"></span><spanlang="en-us"> <font face="Arial" size="2">36.7.1 Returning from a Function</font></span><p
align="LEFT"><spanlang="en-us"></span><a
href="http://www.postgresql.org/docs/8.1/interactive/plpgsql-control-structures.html#PLPGSQL-STATEMENTS-RETURNING"><span
lang="en-us"></span><spanlang="en-us"><u><font color="#0000FF" face="Arial"
size="2">http://www.postgresql.org/docs/8.1/interactive/plpgsql-control-structures.html#PLPGSQL-STATEMENTS-RETURNING</font></u></span><span
lang="en-us"></span></a><spanlang="en-us"></span><span lang="en-us"></span><p align="LEFT"><span lang="en-us"><font
face="Arial"size="2">it appears that</font></span><span lang="en-us"></span><span lang="en-us"> <font face="Arial"
size="2">RETURNNEXT</font></span><span lang="en-us"></span><span lang="en-us"><font face="Arial" size="2"> in a plpgsql
functionrequires you to loop through the result set. Is this correct? If so, I would be happy to post this example to
theinteractive docs</font></span><span lang="en-us"></span><span lang="en-us"><font face="Arial" size="2"> (which could
usea RETURN NEXT example)</font></span><span lang="en-us"></span><span lang="en-us"><font face="Arial" size="2">, but
wantedto make sure</font></span><span lang="en-us"></span><span lang="en-us"><font face="Arial" size="2"> that I
wasn</font></span><spanlang="en-us"></span><span lang="en-us"><font face="Arial" size="2">’</font></span><span
lang="en-us"></span><spanlang="en-us"><font face="Arial" size="2">t missing something more elegant</font></span><span
lang="en-us"></span><spanlang="en-us"><font face="Arial" size="2"> or more efficient</font></span><span
lang="en-us"></span><spanlang="en-us"><font face="Arial" size="2">.</font></span><p align="LEFT"><span
lang="en-us"><fontface="Arial" size="2">Best Regards,</font></span><p align="LEFT"><span lang="en-us"><font
face="Arial"size="2">Robert Davidson</font></span><p align="LEFT"><span lang="en-us"><font face="Arial"
size="2">-----------------------------------------</font></span><palign="LEFT"><span lang="en-us"><font face="Arial"
size="2">CREATETABLE test (textcol varchar(10), intcol int);</font></span><p align="LEFT"><span lang="en-us"><font
face="Arial"size="2">INSERT INTO test VALUES ('a', 1);</font></span><p align="LEFT"><span lang="en-us"><font
face="Arial"size="2">INSERT INTO test VALUES ('a', 2);</font></span><p align="LEFT"><span lang="en-us"><font
face="Arial"size="2">INSERT INTO test VALUES ('b', 5);</font></span><p align="LEFT"><span lang="en-us"><font
face="Arial"size="2">INSERT INTO test VALUES ('b', 6);</font></span><p align="LEFT"><span lang="en-us"><font
face="Arial"size="2">CREATE OR REPLACE FUNCTION ReturnNexting(pText Text) RETURNS SETOF test AS $$</font></span><p
align="LEFT"><spanlang="en-us">        <font face="Arial" size="2">DECLARE</font></span><p align="LEFT"><span
lang="en-us">               <font face="Arial" size="2">rec RECORD;</font></span><p align="LEFT"><span
lang="en-us">       <font face="Arial" size="2">BEGIN</font></span><p align="LEFT"><span lang="en-us">               
<fontface="Arial" size="2">FOR rec IN SELECT * FROM test WHERE textcol = pText LOOP</font></span><p align="LEFT"><span
lang="en-us">                       <font face="Arial" size="2">RETURN NEXT rec;</font></span><p align="LEFT"><span
lang="en-us">               <font face="Arial" size="2">END LOOP;</font></span><p align="LEFT"><span
lang="en-us">               <font face="Arial" size="2">RETURN;</font></span><p align="LEFT"><span lang="en-us">       
<fontface="Arial" size="2">END;</font></span><p align="LEFT"><span lang="en-us"><font face="Arial"
size="2">$$</font></span><palign="LEFT"><span lang="en-us"><font face="Arial" size="2">LANGUAGE
plpgsql;</font></span><palign="LEFT"><span lang="en-us"><font face="Arial" size="2">SELECT * FROM
ReturnNexting('a');</font></span><spanlang="en-us"></span><span lang="en-us"></span>

Re: plpqsql and RETURN NEXT requires a LOOP?

From

"Owen Jacobson"

Date:

21 March 2006, 16:54:58

In general, to do anything useful with RETURN NEXT you need a loop.  However, it doesn't need to be a loop over another
resultset:you can do a computation in a loop, returning values as you go. 

Excuse the outlook-ism.

-Owen

-----Original Message-----
From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org]On Behalf Of Davidson, Robert
Sent: Tuesday, March 21, 2006 9:51 AM
To: pgsql-sql@postgresql.org
Subject: [SQL] plpqsql and RETURN NEXT requires a LOOP?


From my reading of 36.7.1 Returning from a Function
http://www.postgresql.org/docs/8.1/interactive/plpgsql-control-structures.html#PLPGSQL-STATEMENTS-RETURNING
it appears that RETURN NEXT in a plpgsql function requires you to loop through the result set. Is this correct? If so,
Iwould be happy to post this example to the interactive docs (which could use a RETURN NEXT example), but wanted to
makesure that I wasn't missing something more elegant or more efficient. 
Best Regards,
Robert Davidson
-----------------------------------------
CREATE TABLE test (textcol varchar(10), intcol int);
INSERT INTO test VALUES ('a', 1);
INSERT INTO test VALUES ('a', 2);
INSERT INTO test VALUES ('b', 5);
INSERT INTO test VALUES ('b', 6);
CREATE OR REPLACE FUNCTION ReturnNexting(pText Text) RETURNS SETOF test AS $$       DECLARE               rec RECORD;
   BEGIN               FOR rec IN SELECT * FROM test WHERE textcol = pText LOOP                       RETURN NEXT rec;
            END LOOP;               RETURN;       END; 
$$
LANGUAGE plpgsql;
SELECT * FROM ReturnNexting('a');