Re: concatenating hstores in a group by?

Yes, a Timescale hypertable with 500,000,000 rows of about 15 key/value pairs per record.
I'm not sure why there is both a gin & gist index on the hstore, or the merits of each.

Thanks....

 \d t_reading_hstore_sec
                                         Table "public.t_reading_hstore_sec"
   Column   |            Type             | Collation | Nullable |                      Default                      
------------+-----------------------------+-----------+----------+---------------------------------------------------
 key        | bigint                      |           | not null | nextval('t_reading_hstore_sec_key_seq'::regclass)
 timer      | timestamp without time zone |           | not null |
 values_sec | hstore                      |           |          |
Indexes:
    "t_reading_hstore_sec_pkey" PRIMARY KEY, btree (key, timer)
    "t_reading_hstore_sec_timer_idx" btree (timer)
    "t_reading_hstore_sec_timer_key" UNIQUE CONSTRAINT, btree (timer)
    "t_reading_hstore_sec_values_idx_gin" gin (values_sec)
    "t_reading_hstore_sec_values_idx_gist" gist (values_sec)

On Wednesday, January 22, 2025 at 06:34:38 AM GMT+13, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com> wrote:

On 1/19/25 12:09, Brent Wood wrote:
> 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)

To be clear values_sec in t_reading_hstore_sec is the hstore field?

If so what is it's structure?

> 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
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com