Re: Detecting change in event properties

Elliot wrote
> Maybe a custom aggregate that takes the last item in a set?
>
> CREATE OR REPLACE FUNCTION public.last_agg ( anyelement, anyelement )
> RETURNS anyelement LANGUAGE sql IMMUTABLE STRICT AS $$
>          SELECT $2;
> $$;
>
> CREATE AGGREGATE public.last (
>          sfunc    = public.last_agg,
>          basetype = anyelement,
>          stype    = anyelement
> );

Conceptually similar to my array_last_nonnull(array_agg(...)) methodology
and the GUC methodology but has the advantage of saving minimal state
(compared to the array_agg()) and not abusing GUC for storage of the
single-value state.

The example would need the same alteration to the frame clause but otherwise
would appear to work in the manner presumed by the OP's original question.

David J.




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