From: | Paul A Jungwirth <pj(at)illuminatedcomputing(dot)com> |
---|---|
To: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
Cc: | sudalai <sudalait2(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: First Aggregate Funtion? |
Date: | 2015-07-20 15:06:23 |
Message-ID: | CA+renyURWvNyYiR++4zbzuXyzrY0jBgS0ViQYM2Lj0A8B7M=YQ@mail.gmail.com |
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Lists: | pgsql-hackers |
> The above implementation of "first" aggregate returns the first non-NULL item
> value.
I'm curious what advantages this approach has over these FIRST/LAST
functions from the Wiki?:
https://wiki.postgresql.org/wiki/First/last_%28aggregate%29
Also to get the "first non-null value" you can apply an ordering to
just the aggregate function, e.g.:
select first(id order by start_time nulls last) from events;
If you want speed you should probably write a C version.
Is there something I'm missing?
Also since we're on the hackers list is this a proposal to add these
functions to core Postgres?
Yours,
Paul
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