Re: Catching errors inside a LOOP is causing performance issues

On Mon, Sep 25, 2017 at 9:13 AM, Denisa Cirstescu <
Denisa(dot)Cirstescu(at)tangoe(dot)com> wrote:

>
> Can someone please explain to me why this worked?
>
> What happened behind the scenes?
>
> I suspect that when you catch exceptions inside of a LOOP and the code
> ends up generating an exception, Postgres can’t use cached plans to
> optimize that code so it ends up planning the code at each iteration and
> this causes performance issues.
>
> Is my assumption correct?
>
>
>
​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.

David J.