Skip site navigation (1) Skip section navigation (2)

Re: array_agg() NULL Handling

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: "David E(dot) Wheeler" <david(at)kineticode(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: array_agg() NULL Handling
Date: 2010-09-01 07:30:08
Message-ID: AANLkTinQbAptPRsfO8KED2kxpZN=ePNw30AMxLRm14DS@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
2010/9/1 David E. Wheeler <david(at)kineticode(dot)com>:
> The aggregate docs say:
>
>> The first form of aggregate expression invokes the aggregate across all input rows for which the given expression(s) yield non-null values. (Actually, it is up to the aggregate function whether to ignore null values or not — but all the standard ones do.)
>
> -- http://developer.postgresql.org/pgdocs/postgres/sql-expressions.html#SYNTAX-AGGREGATES
>
> That, however, is not true of array_agg():
>
> try=# CREATE TABLE foo(id int);
> CREATE TABLE
> try=# INSERT INTO foo values(1), (2), (NULL), (3);
> INSERT 0 4
> try=# select array_agg(id) from foo;
>  array_agg
> ──────────────
>  {1,2,NULL,3}
> (1 row)
>
> So are the docs right, or is array_agg() right?

Docs is wrong :) I like current implementation. You can remove a NULLs
from aggregation very simply, but different direction isn't possible

Regards
Pavel Stehule
>
> Best,
>
> David
>
>
> --
> Sent via pgsql-hackers mailing list (pgsql-hackers(at)postgresql(dot)org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-hackers
>

In response to

Responses

pgsql-hackers by date

Next:From: Fujii MasaoDate: 2010-09-01 07:53:38
Subject: Re: Synchronous replication - patch status inquiry
Previous:From: Heikki LinnakangasDate: 2010-09-01 07:11:39
Subject: Re: Interruptible sleeps (was Re: CommitFest 2009-07: Yay, Kevin! Thanks, reviewers!)

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group