I have to say, this seems straightforward to me. An array with N elements gets N rows in the result set. I'm curious what other behavior would be more reasonable.
On Thu, Jan 3, 2013 at 11:22 AM, Jeff Trout <threshar@xxxxxxxxxxxxxxxxxx> wrote:
I just ran into an interesting thing with unnest and empty arrays.
create table x (
a int,
b int[]
);
insert into x(a,b) values (1, '{}');
insert into x(a,b) values (1, '{}');
insert into x(a,b) values (1, '{}');
select a, b from x;
select a, unnest(b) from x;
insert into x(a,b) values (2, '{5,6}');
select a, unnest(b) from x;
drop table x;
gives me:
CREATE TABLE
INSERT 0 1
INSERT 0 1
INSERT 0 1
a | b
---+----
1 | {}
1 | {}
1 | {}
(3 rows)
a | unnest
---+--------
(0 rows)
INSERT 0 1
a | unnest
---+--------
2 | 5
2 | 6
(2 rows)
DROP TABLE
I can understand the likely reasoning behind the behavior but perhaps a note in the documentation about it might be of use for others that may get bit by this functionality. (especially given the structure of the query, had I been doing select * from unnest(arr) that would be more intuitive, but given the query structure of select with no where the results can be surprising.)
thanks
--
Jeff Trout <jeff@xxxxxxxxxxxxx>
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