Postgres 12

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Help with an interesting Postgres question: Why isn't an Index Only Scan used on a partition accessed via the parent table?.

create table tt8 (c1 numeric);
insert into tt8 values
(1),(2),(3),(6),(7),(8),(9),(12),(14);
9 rows affected

select min(c1) || (case when count(*) = 1 then '' else '-' || max(c1) end)
from (select tt8.*, row_number() over (order by c1) as seqnum
      from tt8
     ) t
group by (c1 - seqnum);


?column?


12

6-9

1-3

14


    select string_agg(val, ',' order by min_c1)
    from (select min(c1) || (case when count(*) = 1 then '' else '-' || max(c1) end) as val, min(c1) as min_c1
          from (select tt8.*, row_number() over (order by c1) as seqnum
                from tt8
               ) t
          group by (c1 - seqnum)
         ) t;



string_agg


1-3,6-9,12,14