Re: BUG #16443: Too much memory usage on insert query

PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
> I was executing this query:
> insert into ct_entry_chain (ct_entry_id, certificate_id) select id,
> unnest(certificate_chain_id) from ct_entry;

How much data is that?

> The process was using at least 14 GB, of the 8 GB of RAM that's available.

My first guess is that the space was being eaten by trigger list entries
to verify the foreign-key constraints on the target table. You might be
better advised to fill the new table first and then create its FK
constraints. (Building the indexes afterwards wouldn't be a bad idea,
either.)

We are looking at better mechanisms for handling FK verification, but
that won't see the light of day before v14 at the earliest.

regards, tom lane