Re: plpgsql merge func question

On Fri, Dec 20, 2013 at 6:42 AM, Andreas Kretschmer
<akretschmer@spamfence.net> wrote:
> Matthias Leopold <matthias@aic.at> wrote:
>
>> hi,
>>
>> i tried to write a merge function in plpgsql, which is derived from the
>> example in the docs (Example 38-2 in
>> http://www.postgresql.org/docs/8.4/static/plpgsql-control-structures.html).
>> Code is below. This works fine as long as entries in count_table have
>> todays date in "datum". when i have older entries the function "locks
>> up" (doesn't return, server has 100% cpu). i'm a plpgsql novice. can
>> someone explain why this happens? related question: i didn't find a way
>
> Can't reproduce, works for me.

Almost certainly a  non-'unique_violation' exception is being thrown
(perhaps from a dependent trigger). In a loop like that there should
always be a handler of last resort.  I bitterly griped about this
example a few years back (search the archives).   TBH, many times I've
wished that caught-but-unhandled exceptions were re-thrown by default.

Unless high concurrency is needed, for merge functionality it makes a
lot more sense to just lock the table before the insert instead of
rigging a loop.