Re: backend dies suddenly after a lot of error messages

Mirko Kaffka <mirko(at)interface-business(dot)de> wrote:
> We have problems with backend processes that close the channel because of
> palloc() failures. When an INSERT statement fails, the backend reports an
> error (e.g. `Cannot insert a duplicate key into a unique index') and
> allocates a few bytes more memory. The next SQL statement that fails
> causes the backend to allocate more memory again, etc. until we have no
> more virtual memory left. Is this a bug?
> We are using postgres 6.4.2 on FreeBSD 2.2.8.

I have found the primary cause of memory leakage after an error ---
basically, the backend forgets to free *any* of the temporary memory
allocated up to the point of the error :-(. If your applications tend
to provoke many SQL errors then you will see a backend process that eats
up more and more memory until it hits your local system's process size
limit, whereupon it crashes.

I have repaired this problem in the 6.5 development sources. Attached
is a patch for 6.4.2, which I suggest you apply if this sounds like a
problem you are having.

The patch does not completely eliminate memory leaks after errors, but
they seem to be reduced to the few-hundred-bytes-per-error range instead
of the kilobytes (potentially lots of kilobytes) range. I am working on
curing the problem more completely for 6.5.

regards, tom lane