On 21. 09. 21 23:34, Michael Lewis wrote:
Related to this current discussion and exchange of ideas... is there a
best practice for retrieving data in such a way as the rows are
localized to a timezone for where/group by purposes. That is, if I
have a table which has events, but those events belong to a tenant or
some entity that has a location which implies a timezone (or at least
an offset), is there a best way to write a query similar to the below?
Please forgive and overlook if there is some obvious syntax error, as
this is just a quick and dirty example. Might it make sense to store a
"localized" version of the timestamp *without* timezone on the event
record such that an index can be used for fast retrieval and even
grouping?
select
date_trunc( 'month', e.event_datetime AT TIMEZONE t.time_zone_name )
AS event_date,
count( e.id <http://e.id> )
from events AS e
join tenants AS t ON t.id <http://t.id> = e.tenant_id
where e.event_datetime AT TIMEZONE t.time_zone_name >=
'01/01/2021'::DATE AND e.event_datetime AT TIMEZONE t.time_zone_name <
'09/01/2021'::DATE;
This is an interesting case. A simplified query example would be to
"give me all events for this year".
I am not sure what the cost of shifting UTC is, probably not much, but
depending on use case it might make sense to deconstruct into date and
time for query optimization.
