Memory leak during delete with sequential scan

Hi,

On one of our production servers postgres backend processes are killed by
linux OOM killer. It runs 9.1.13 version now.

Using the method described here
http://www.depesz.com/2012/06/09/how-much-ram-is-postgresql-using/ I was
able to find out that processes which are killed use a lot of private
memory ~3Gb. It turns out that memory consumption grows when a particular
query is executed namely delete with filtering when sequential scan is
used.

The simplified test which demonstrates this problem.

$ psql -U postgres postgres
psql (9.1.11, server 9.3.5)

postgres=# create table t (i integer, t text);
CREATE TABLE

postgres=# insert into t select v,
'01234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789'
|| text(v) from generate_series(1,4000000) v;
INSERT 0 4000000

postgres=# \q

restart postgres

$ psql -U postgres postgres

execute 500 times the following command in the same connection
postgres=# delete from t where t = '';

On my setup of 9.3.5 this causes postgres backend process to consume 130Mb
of private memory which seems is reclaimed only when connection is closed.
On 9.1.13 this consumes about 250Mb.

I was able to find that this problem happens on 9.1.13, 9.2.9 and 9.3.5.
Note that this doesn't happen on latest 9.1.14 - memory usage is about 26
Mb after the above scenario.
On 9.4beta2 the memory consumption grows very much like on 9.3.5 but after
about a minute of connection being IDLE it decreases.

If I add index on the field which is used for filtering private memory
consumption is much smaller (2-10 Mb).

This problem can be reliably reproducible only after restart of postgres.
After some time when some statements are executed on the database the
problem sometimes gone.

Using of a connection pool makes this problem more painful.
My initial intention was to upgrade to 9.3 but it also has this problem.

This looks very much like a bug for me which affects latest stable version
(9.3.5) but I'm not sure that my method to diagnose the problem is correct.
Should I fine a bug regarding this?

Regards,
Roman Konoval