irate_left()

Since 1.3.0

Calculate the instantaneous rate of change at the left, or earliest, edge of a counter aggregate. This is equal to the second value minus the first value, divided by the time lapse between the two points, after accounting for resets. This calculation is useful for fast-moving counters.

Samples

Get the instantaneous rate of change at the start of each 15-minute counter aggregate.

SELECT
    id,
    bucket,
    irate_left(summary)
FROM (
    SELECT
        id,
        time_bucket('15 min'::interval, ts) AS bucket,
        counter_agg(ts, val) AS summary
    FROM foo
    GROUP BY id, time_bucket('15 min'::interval, ts)
) t

Arguments

The syntax is:

irate_left(
  summary CounterSummary
) RETURNS DOUBLE PRECISION

Name	Type	Default	Required	Description
summary	CounterSummary	-	✔	A counter aggregate created using counter_agg

Returns

Column	Type	Description
irate_left	DOUBLE PRECISION	The instantaneous rate of change at the left, or earliest, edge of the counter aggregate