first_val, last_val

This pair of functions returns the values of the first and last points in a CounterSummary aggregate.

first_val(
    cs CounterSummary
) RETURNS DOUBLE PRECISION
last_val(
    cs CounterSummary
) RETURNS DOUBLE PRECISION

Required arguments

Returns

Sample usage

This example produces a CounterSummary from timestamps and associated values, then applies the first_val and last_val accessors:

WITH t as (
    SELECT
        time_bucket('1 day'::interval, ts) as dt,
        counter_agg(ts, val) AS cs -- get a CounterSummary
    FROM table
    GROUP BY time_bucket('1 day'::interval, ts)
)
SELECT
    dt,
    first_val(cs) -- extract the value of the first point in the CounterSummary
    last_val(cs) -- extract the value of the last point in the CounterSummary
FROM t;