interpolated_delta()

interpolated_delta()

Calculate the change in a counter over a time period. Data points at the exact boundaries of the time period aren’t needed. The function interpolates the counter values at the boundaries from adjacent CounterSummaries if needed.


interpolated_delta(
    summary CounterSummary,
    start TIMESTAMPTZ,
    interval INTERVAL,
    prev CounterSummary,
    next CounterSummary
) RETURNS DOUBLE PRECISION

For more information about counter aggregation functions, see the hyperfunctions documentation.

Required arguments

Name	Type	Description
`summary`	`CounterSummary`	The input `CounterSummary` from a `counter_agg` call
`start`	`TIMESTAMPTZ`	The start of the interval which the delta should be computed over (if there is a preceeding point)
`interval`	`INTERVAL`	The length of the interval which the delta should cover

Optional arguments

Name	Type	Description
`prev`	`CounterSummary`	The `CounterSummary` from the prior interval, used to interpolate the value at `start`. If `NULL`, the first timestamp in `summary` is used as the start of the interval.
`next`	`CounterSummary`	The `CounterSummary` from the following interval, used to interpolate the value at `start` + `interval`. If `NULL`, the last timestamp in `summary` is used as the end of the interval.

Returns

Name	Type	Description
`interpolated_delta`	`DOUBLE PRECISION`	The delta between the first and last points of the time interval. If exact values are missing in the raw data for the first and last points, these values are interpolated linearly from the neighboring `CounterSummaries`

Sample usage


SELECT
    id,
    bucket,
    interpolated_delta(
        summary,
        bucket,
        '15 min',
        LAG(summary) OVER (PARTITION BY id ORDER by bucket),
        LEAD(summary) OVER (PARTITION BY id ORDER by bucket)
    )
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