HPE's Vertica database has a proprietary extension used for generating
timeseries data. I am trying to figure out how to invoke it from Sequel
with minimal hullabaloo.
Here's an example of the kind of query I'm trying to build:
SELECT slice_time,
round(ts_last_value(a_column IGNORE NULLS, 'linear')) AS a_col
FROM(
select occurred_at,
a_column
FROM a_table
WHERE something = 'something else'
) subq -- this is not used, but the parser requires a name here
TIMESERIES slice_time AS '1 second' OVER(ORDER BY occurred_at)
I can build the subquery with:
subquery = DB.from(:a_table).select(:occurred_at,
:a_column).where(something: 'something_else')
I can then compose it into the outer query with
DB.from(subquery).select { |o| [o.slice_time,
o.round(o.ts_last_value(Sequel.lit("a_column IGNORE NULLS"),
'linear')).as(:a_col)] }
but I can't figure out how to add the TIMESERIES clause to the query. I
don't mind dropping into Sequel.lit if required (as you can see), but I
need to get a dataset back, since this query will itself be included into
another query as a subquery. Any suggestions are greatly appreciated.
BTW, if there's a better way to do the round(ts_last_value(...)) bit, I'm
not super-thrilled with how that looks (it works fine, though).
-=Eric
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