Обсуждение: [BUGS] BUG #14626: array_agg( anyarray ) unexpected error with multi-valuedsingle-dimension array
[BUGS] BUG #14626: array_agg( anyarray ) unexpected error with multi-valuedsingle-dimension array
От
david.g.johnston@gmail.com
Дата:
The following bug has been logged on the website: Bug reference: 14626 Logged by: David Johnston Email address: david.g.johnston@gmail.com PostgreSQL version: 9.5.6 Operating system: Ubuntu 14.04 Description: In short... This works: SELECT array_agg(CASE WHEN a = ARRAY[]::text[] THEN ARRAY['N/A']::text[] ELSE a END) FROM ( VALUES (1, ARRAY[]::text[]), (1, ARRAY['1']::text[]) ) vals (v, a); This doesn't, and should since the number of elements in the non-empty array shouldn't change the dimensionality logic. SELECT array_agg(CASE WHEN a = ARRAY[]::text[] THEN ARRAY['N/A']::text[] ELSE a END) FROM ( VALUES (1, ARRAY[]::text[]), (1, ARRAY['1','2']::text[]) ) vals (v, a) David J. -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
david.g.johnston@gmail.com writes:
> This doesn't, and should since the number of elements in the non-empty array
> shouldn't change the dimensionality logic.
> SELECT array_agg(CASE WHEN a = ARRAY[]::text[] THEN ARRAY['N/A']::text[]
> ELSE a END)
> FROM ( VALUES (1, ARRAY[]::text[]), (1, ARRAY['1','2']::text[]) ) vals (v,
> a)
Why do you think that should work? You're asking array_agg to accumulate
a 1-D length-1 array and then a 1-D length-2 array. There's no way to
make a rectangular 2-D array out of that, except perhaps by inventing
entries which isn't in array_agg's charter.
regards, tom lane
--
Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-bugs
Re: [BUGS] BUG #14626: array_agg( anyarray ) unexpected error withmulti-valued single-dimension array
От
"David G. Johnston"
Дата:
david.g.johnston@gmail.com writes:
> This doesn't, and should since the number of elements in the non-empty array
> shouldn't change the dimensionality logic.
> SELECT array_agg(CASE WHEN a = ARRAY[]::text[] THEN ARRAY['N/A']::text[]
> ELSE a END)
> FROM ( VALUES (1, ARRAY[]::text[]), (1, ARRAY['1','2']::text[]) ) vals (v,
> a)
Why do you think that should work? You're asking array_agg to accumulate
a 1-D length-1 array and then a 1-D length-2 array. There's no way to
make a rectangular 2-D array out of that, except perhaps by inventing
entries which isn't in array_agg's charter.
I was being too narrow-minded in interpreting the word dimension.
SELECT array_ndims(ARRAY['1','2']::text[]); => 1; therefore it is a one dimensional array - having a length of 2. One can, and we do in other places, define that array as having a dimension of 1x2.
SELECT '{{N/A},{1,2}}'::text[] --> fails with "sub-arrays with matching dimensions"...
Apparently the annoyance I posted on the other thread isn't so simple to resolve - just having an empty "1-dimensional" array is not particularly useful given the length dimension must also match.
This helps explain why my first attempt:
SELECT array_dims('{1,2}'::text[]); --> yields [1:2] which is what is being keyed off here.
All this and all I really want is a friggin' "array_append / array_concat" aggregate function that accepts either scalars or matching "primary dimension" arrays - and treats empty arrays as no-ops.
David J.
Re: [BUGS] BUG #14626: array_agg( anyarray ) unexpected error withmulti-valued single-dimension array
От
"David G. Johnston"
Дата:
david.g.johnston@gmail.com writes:
> This doesn't, and should since the number of elements in the non-empty array
> shouldn't change the dimensionality logic.
> SELECT array_agg(CASE WHEN a = ARRAY[]::text[] THEN ARRAY['N/A']::text[]
> ELSE a END)
> FROM ( VALUES (1, ARRAY[]::text[]), (1, ARRAY['1','2']::text[]) ) vals (v,
> a)
Why do you think that should work? You're asking array_agg to accumulate
a 1-D length-1 array and then a 1-D length-2 array. There's no way to
make a rectangular 2-D array out of that, except perhaps by inventing
entries which isn't in array_agg's charter.All this and all I really want is a friggin' "array_append / array_concat" aggregate function that accepts either scalars or matching "primary dimension" arrays - and treats empty arrays as no-ops.
In the end I realized that serializing the arrays to text would work just fine. The extra I/O for converting from and to an actual array type is immaterial in my situation. It still doesn't remove my actual desire for an aggregate array_concat type function, and the for a rectangular array is a bit annoying (i.e., allow non-rectangular and just report an out-of-bounds error on attempts to explicitly access non-existent elements) but that's easy enough to toss in with the other peculiarities in this area.
SELECT unnest(array_agg)::text[]
FROM (
SELECT array_agg(a)
FROM ( VALUES (1, ARRAY[]::text[]::text), (1, ARRAY['1','2']::text[]::text) ) vals (v, a)
) txt_arrays;
David J.