aggregate arrays

Dmitry E. Oboukhov wrote:

example:

a query returns a column that contains arrays:

select * FROM (VALUES (ARRAY[1,2,3,3,4], 1), (ARRAY[1,2,2,3,4], 2)) t;
column1 | column2
-------------+---------
{1,2,3,3,4} | 1
{1,2,2,3,4} | 2
(2 rows)

and then we want aggregate that result.

example by column2:

WITH "test" AS (
select * FROM (VALUES (ARRAY[1,2,3,3,4], 1), (ARRAY[1,2,2,3,4], 2)) t
)

SELECT array_agg(column2) column2 FROM "test";
column2
---------
{1,2}
(1 row)

and I want aggregate column1 arrays into one array. I want receive the
result:

column1 | column2
----------------------+-------------
{1,2,3,3,4,1,2,2,3,4} | {1,2}

I've tried the statement:

WITH "test" AS (
select * FROM (VALUES (ARRAY[1,2,3,3,4], 1), (ARRAY[1,2,2,3,4], 2)) t
)

SELECT
array_agg(unnest(column1)) AS column1,
array_agg(column2) column2
FROM
"test";

But I receive the error:

ERROR: set-valued function called in context that cannot accept a set

How can I aggregate arrays into one array?

Create your own aggregate.

CREATE AGGREGATE array_union (anyarray) (SFUNC = array_cat, STYPE = anyarray);

WITH "test" AS (
select * FROM (VALUES (ARRAY[1,2,3,3,4], 1), (ARRAY[1,2,2,3,4], 2)) t
)
SELECT
array_union(column1) AS column1,
array_agg(column2) column2
FROM
"test";

column1 | column2
-----------------------+---------
{1,2,3,3,4,1,2,2,3,4} | {1,2}
(1 row)

Yours,
Laurenz Albe