long transactions / backend memory usage

Dear all,

We have run into a case where we run a long transaction, and during the
transaction the backend process's memory usage is growing constantly.

I've written a script to simulate this, please someone confirm if it is
normal or not.

The script just inserts and removes rows in a table in a single
transaction. If given a parameter, the same row is being inserted and
removed.

The latter case also produces constantly increasing backend process memory
usage.

Create the table as in the script, and after run:

$ perl pqtest.pl 5

I've been running the script for nearly 40 minutes right now, it has done
120k iterations, and the RSS of the postgresql process is still growing.

This can be reproduced on 9.3 and 9.4 also.

Thanks in advance,
Kojedzinszky Richárd
Euronet Magyarorszag Informatika Zrt.