first_val()

Since 1.11.0

Get the value of the first point from a counter aggregate.

Samples

Get the first and last value of each daily counter aggregate.

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;

Arguments

The syntax is:

first_val(
    cs CounterSummary
) RETURNS DOUBLE PRECISION

Name	Type	Default	Required	Description
cs	CounterSummary	-	✔	A counter aggregate produced using counter_agg

Returns

Column	Type	Description
first_val	DOUBLE PRECISION	The value of the first point in the counter aggregate