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Thanks for the replies, appreciated...
My current solution is:
select trip_code,
station_no,
timer_sec + interval '12 hour' as NZST,
timer_sec as utc,
hstore_to_json(string_agg(values_sec::text, ', ')::hstore) as values_sec
from (select '$TRIP' as trip_code,
$STATION as station_no,
date_trunc('second', timer) as timer_sec,
values_sec
from t_reading_hstore_sec
where timer >= '$ISO_S'::timestamp - interval '12 hour'
and timer <= '$ISO_F'::timestamp - interval '12 hour') as foo
group by timer_sec, trip_code, station_no;
Convert the hstore to text, aggregate the text with string_agg(), convert back to hstore (which seems to remove duplicate keys, OK for my purpose)
and group by timer truncated to whole seconds. I also provide UTC & local timezone times for each set of readings. It is run in a bash script which passes the trip & station values to the query, as well as the start/finish times as ISO format strings.
The output is going to a Sqlite3 (Spatialite) database, which does not have hstore, or all the hstore functionality that Postgres has, but does have a json datatype which is adequate for our purposes, hence the hstore_to_json in the query.
Thanks again,
Brent Wood
Principal Technician, Fisheries NIWA DDI: +64 (4) 3860529 From: David G. Johnston <david.g.johnston@xxxxxxxxx>
Sent: Monday, January 20, 2025 04:28 To: Brent Wood <Brent.Wood@xxxxxxxxxx> Cc: pgsql-general@xxxxxxxxxxxxxxxxxxxx <pgsql-general@xxxxxxxxxxxxxxxxxxxx> Subject: concatenating hstores in a group by? On Friday, January 17, 2025, Brent Wood <Brent.Wood@xxxxxxxxxx> wrote:
There are no hstore aggregate functions. You’ll want to convert them to,json first then use the json_objectagg aggregate function.
David J.
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