Re: Catching errors inside a LOOP is causing performance issues

"David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> ​Not sure how much detail you are looking for but the docs say this:
> "​Tip: A block containing an EXCEPTION clause is significantly more
> expensive to enter and exit than a block without one. Therefore, don't use
> EXCEPTION without need."
> https://www.postgresql.org/docs/current/static/plpgsql-control-structures.html#PLPGSQL-ERROR-TRAPPING

> I'm somewhat doubting "plan caching" has anything to do with this; I
> suspect its basically that there is high memory and runtime overhead to
> deal with the possibilities of needing to convert a exception into a branch
> instead of allowing it to be fatal.

Yeah, it's about the overhead of setting up and ending a subtransaction.
That's a fairly expensive mechanism, but we don't have anything cheaper
that is able to recover from arbitrary errors.

regards, tom lane