How to troubleshoot high mem usage by postgres?

Hi, I'm having an issue where a postgres process is taking too much
memory when performing many consecutive inserts and updates from a PHP
script (running on the command line). I would like to know what sort
of logging I can turn on to help me determine what is causing memory
to be consumed and not released.

Most PHP scripts are not long-running and properly releasing the
resources using the provided functions in the pgsql PHP extension is
not necessary. However since I do have a long-running script, I have
taken steps to ensure everything is being properly released when it is
no longer needed (I am calling the functions provided, but I don't
know if the pgsql extension is doing the right thing). In spite of
this, the longer the script runs and processes records, the more
memory increases. It increases to the point that system memory is
exhausted and it starts swapping. I killed the process at this point.

I monitored the memory with top. here are the results.. the first is
10 seconds after my script started running. The second is about 26
seconds.

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ DATA COMMAND
17461 postgres 16 0 572m 405m 14m S 20.0 10.7 0:10.65 422m postmaster
17460 root 15 0 136m 14m 4632 S 10.6 0.4 0:06.16 10m php
17462 postgres 15 0 193m 46m 3936 D 3.3 1.2 0:01.77 43m postmaster

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ DATA COMMAND
17461 postgres 16 0 1196m 980m 17m S 19.0 26.0 0:25.72 1.0g postmaster
17460 root 15 0 136m 14m 4632 R 10.3 0.4 0:14.31 10m php
17462 postgres 16 0 255m 107m 3984 R 3.0 2.9 0:04.19 105m postmaster

If I am indeed doing everything I can to release the resources (and
I'm 95% sure I am) then it looks like the pgsql extension is at fault
here.
Regardless of who/what is at fault, I need to fix it. And to do that I
need to find out what isn't getting released properly. How would I go
about that?

Thanks,
Chris