Question

I have a table like this:

                         Table "public.statistics"

id         | integer                | not null default nextval('statistics_id_seq'::regclass)
goals      | hstore                 | 

items:

|id    |goals                  |
|30059 |"3"=>"123"             |
|27333 |"3"=>"200", "5"=>"10"  |

What I need to do for aggregate all values by key in hash?

I want to get result like this:

select sum(goals) from statistics

return

|goals                 |
|"3"=>"323", "5"=>"10" |

Answer 1

Building on Laurence’s answer, here’s a pure SQL way to aggregate the summed key/value pairs into a new hstore using array_agg and the hstore(text[], text[]) constructor.

http://sqlfiddle.com/#!1/9f1fb/17

SELECT hstore(array_agg(hs_key), array_agg(hs_value::text))
FROM (
  SELECT
    s.hs_key, sum(s.hs_value::integer)
  FROM (
    SELECT (each(goals)).* FROM statistics
  ) as s(hs_key, hs_value)
  GROUP BY hs_key
) x(hs_key,hs_value)

I’ve also replaced to_number with a simple cast to integer and simplified the key/value iteration.