BUG #8279: Apparent memory leak with use of INTO STRICT in plpgsql?

The following bug has been logged on the website:

Bug reference: 8279
Logged by: Chad
Email address: chad(dot)wagner(at)gmail(dot)com
PostgreSQL version: 9.2.4
Operating system: Ubuntu 10.04
Description:

If I use the "SELECT ... INTO STRICT" clause with plpgsql it appears to leak
memory, until I disconnect my session and the backend dies. If I remove the
"INTO STRICT" clause then there is no apparent memory leak.

Below is a test case to reproduce on 9.2.4, and the pmap diff of
before/after on the backend process.

Pmap on backend process (diff of before/after), about a 400MB leak:
--- x1.out 2013-07-03 21:50:02.472438435 -0400
+++ x2.out 2013-07-03 21:51:02.462435759 -0400
@@ -1,5 +1,9 @@
11945: postgres: wagnerch wagnerch [local] idle

Address Kbytes RSS Anon Locked Mode Mapping
+00007f4aae074000 148 - - - r-x-- plpgsql.so
+00007f4aae099000 2048 - - - ----- plpgsql.so
+00007f4aae299000 8 - - - r---- plpgsql.so
+00007f4aae29b000 4 - - - rw--- plpgsql.so
00007f4aae29c000 252 - - - r---- LC_CTYPE
00007f4aae2db000 560320 - - - rw-s- [ shmid=0xa9c8000
]
00007f4ad060b000 48 - - - r-x--
libnss_files-2.11.1.so
@@ -129,9 +133,9 @@
00007f4ad4c36000 116 - - - r---- postgres
00007f4ad4c53000 52 - - - rw--- postgres
00007f4ad4c60000 364 - - - rw--- [ anon ]
-00007f4ad5f8b000 1192 - - - rw--- [ anon ]
+00007f4ad5f8b000 415820 - - - rw--- [ anon ]
00007ffff3396000 144 - - - rw--- [ stack ]
00007ffff33c6000 4 - - - r-x-- [ anon ]
ffffffffff600000 4 - - - r-x-- [ anon ]
---------------- ------ ------ ------ ------
-total kB 632108 - - -
+total kB 1048944 - - -

Test case:

/*

CREATE TABLE head_tb AS
SELECT generate_series (1, 30) AS id;

CREATE TABLE det_tb AS
SELECT a.a header_id, b.b detail_id, rpad ('X', 1000, 'X') AS data
FROM generate_series (1,30) AS a, generate_series (1, 50000) AS b;

CREATE INDEX det_tb_n1 ON det_tb (header_id);
CREATE UNIQUE INDEX det_tb_u1 ON det_tb (header_id, detail_id);

*/

DO LANGUAGE plpgsql
$$
DECLARE
l_head_rec RECORD;
l_det_rec RECORD;
l_next_det_rec RECORD;
BEGIN
FOR l_head_rec IN
SELECT id,
LEAD (id) OVER (
ORDER BY id
RANGE BETWEEN UNBOUNDED PRECEDING
AND UNBOUNDED FOLLOWING
) next_id
FROM head_tb
ORDER BY id
LOOP
FOR l_det_rec IN
SELECT *
FROM det_tb
WHERE header_id = l_head_rec.id
LOOP
BEGIN
SELECT *
INTO STRICT l_next_det_rec
FROM det_tb
WHERE detail_id = l_det_rec.detail_id
AND header_id = l_head_rec.next_id;

EXCEPTION
WHEN NO_DATA_FOUND
THEN
NULL;
END;
END LOOP;
END LOOP;
END;
$$;