Thread

1. Proposal: array_unique_agg() function

   Aleksander Alekseev <aleksander@timescale.com> — 2022-03-01T13:39:34Z

   Hi hackers,
   
   I needed an aggregate function similar to array_agg() but which
   aggregates only unique values. As it turned out there is no convenient
   way of doing this. What I ended up doing instead was aggregating to
   JSONB keys and then converting a JSONB object to an array:
   
   SELECT array(select jsonb_object_keys(jsonb_object_agg(mycolumn, true)))
   FROM ...
   
   This works but doesn't seem to be the greatest user experience. I
   would like to submit a patch that adds array_unique_agg() function
   unless anyone has strong objections to this feature.
   
   -- 
   Best regards,
   Aleksander Alekseev
   
   
   
   

2. Re: Proposal: array_unique_agg() function

   Pavel Stehule <pavel.stehule@gmail.com> — 2022-03-01T13:46:53Z

   Hi
   
   út 1. 3. 2022 v 14:39 odesílatel Aleksander Alekseev <
   aleksander@timescale.com> napsal:
   
   > Hi hackers,
   >
   > I needed an aggregate function similar to array_agg() but which
   > aggregates only unique values. As it turned out there is no convenient
   > way of doing this. What I ended up doing instead was aggregating to
   > JSONB keys and then converting a JSONB object to an array:
   >
   > SELECT array(select jsonb_object_keys(jsonb_object_agg(mycolumn, true)))
   > FROM ...
   >
   > This works but doesn't seem to be the greatest user experience. I
   > would like to submit a patch that adds array_unique_agg() function
   > unless anyone has strong objections to this feature.
   >
   
   SELECT array_agg(DISTINCT ...) doesn't help?
   
   Regards
   
   Pavel
   
   
   >
   > --
   > Best regards,
   > Aleksander Alekseev
   >
   >
   >
   

3. Re:Proposal: array_unique_agg() function

   Sergei Kornilov <sk@zsrv.org> — 2022-03-01T13:48:48Z

   Hello
   
   select array_agg(distinct mycolumn) from 
   
   from the very beginning? Even the 7.1 manual describes such a syntax: https://www.postgresql.org/docs/7.1/sql-expressions.html
   
   regards, Sergei
   
   
   
   

4. Re: Proposal: array_unique_agg() function

   Aleksander Alekseev <aleksander@timescale.com> — 2022-03-01T13:54:23Z

   Pavel, Sergei,
   
   > SELECT array_agg(DISTINCT ...) doesn't help?
   
   It works, many thanks!
   
   -- 
   Best regards,
   Aleksander Alekseev