eliminate duplicate array values in postgres

Question

I have an array of type bigint, how can I remove the duplicate values in that array?

Ex: array[1234, 5343, 6353, 1234, 1234]

I shou

Answer 1

Here's the "inline" way:

SELECT 1 AS anycolumn, (
  SELECT array_agg(c1)
  FROM (
    SELECT DISTINCT c1
    FROM (
      SELECT unnest(ARRAY[1234,5343,6353,1234,1234]) AS c1
    ) AS t1
  ) AS t2
) AS the_array;

First we create a set from array, then we select only distinct entries, and then aggregate it back into array.

Answer 2

Using DISTINCT implicitly sorts the array. If the relative order of the array elements needs to be preserved while removing duplicates, the function can be designed like the following: (should work from 9.4 onwards)

CREATE OR REPLACE FUNCTION array_uniq_stable(anyarray) RETURNS anyarray AS
$body$
SELECT
    array_agg(distinct_value ORDER BY first_index)
FROM 
    (SELECT
        value AS distinct_value, 
        min(index) AS first_index 
    FROM 
        unnest($1) WITH ORDINALITY AS input(value, index)
    GROUP BY
        value
    ) AS unique_input
;
$body$
LANGUAGE 'sql' IMMUTABLE STRICT;