Re: array_agg() NULL Handling

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
>
>
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