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.johns...@gmail.com>
Sent: Monday, January 20, 2025 04:28
To: Brent Wood <brent.w...@niwa.co.nz>
Cc: pgsql-general@lists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: concatenating hstores in a group by?
On Friday, January 17, 2025, Brent Wood
<brent.w...@niwa.co.nz<mailto:brent.w...@niwa.co.nz>> wrote:
I want to concatenate the hstores,
There are no hstore aggregate functions. You’ll want to convert them to,json
first then use the json_objectagg aggregate function.
David J.
[https://www.niwa.co.nz/static/niwa-2018-horizontal-180.png]
<https://www.niwa.co.nz>
Brent Wood
Principal Technician - GIS and Spatial Data Management
Programme Leader - Environmental Information Delivery
+64-4-386-0529
National Institute of Water & Atmospheric Research Ltd (NIWA)
301 Evans Bay Parade Hataitai Wellington New Zealand
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