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

... Where the statandard libraries (?) for this kind of array_X utility??

Try to search... See some but no standard:

• postgres.cz/wiki/Array_based_functions: good reference!

• JDBurnZ/postgresql-anyarray, good initiative but needs some collaboration to enhance.

• wiki.postgresql.org/Snippets, frustrated initiative, but "offcial wiki", needs some collaboration to enhance.

• MADlib: good! .... but it is an elephant, not an "pure SQL snippets lib".

---

Simplest and faster array_distinct() snippet-lib function

Here the simplest and perhaps faster implementation for array_unique() or array_distinct():

CREATE FUNCTION array_distinct(anyarray) RETURNS anyarray AS $f$
  SELECT array_agg(DISTINCT x) FROM unnest($1) t(x);
$f$ LANGUAGE SQL IMMUTABLE;

---

NOTE: it works as expected with any datatype, except with array of arrays,

SELECT  array_distinct( array[3,3,8,2,6,6,2,3,4,1,1,6,2,2,3,99] ), 
        array_distinct( array['3','3','hello','hello','bye'] ), 
        array_distinct( array[array[3,3],array[3,3],array[3,3],array[5,6]] );
 -- "{1,2,3,4,6,8,99}",  "{3,bye,hello}",  "{3,5,6}"

the "side effect" is to explode all arrays in a set of elements.

PS: with JSONB arrays works fine,

SELECT array_distinct( array['[3,3]'::JSONB, '[3,3]'::JSONB, '[5,6]'::JSONB] );
 -- "{"[3, 3]","[5, 6]"}"

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Edit: more complex but useful, a "drop nulls" parameter

CREATE FUNCTION array_distinct(
      anyarray, -- input array 
      boolean DEFAULT false -- flag to ignore nulls
) RETURNS anyarray AS $f$
      SELECT array_agg(DISTINCT x) 
      FROM unnest($1) t(x) 
      WHERE CASE WHEN $2 THEN x IS NOT NULL ELSE true END;
$f$ LANGUAGE SQL IMMUTABLE;