Greg Mitchell <gmitchell@atdesk.com> writes:
> As far as memory management goes, do I just use hash_create() and assign
> that pointer to fn_extra and at the end of the query it will be freed?
> Or will it not be freed until this end of the transaction? I'm really
> having trouble understanding the memory management issues with Postgres.

You have to be careful that the hashtable is created in the correct
"memory context" --- in this case you want it to be in a query-lifespan
context, not the short-term (per-tuple-lifespan) context that your
function will be called in. The usual procedure for cases like this is
to use the context identified by fn_mcxt. src/backend/utils/mmgr/README
might make useful reading for you.

regards, tom lane

---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match