interpolated_rate()

interpolated_rate()

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

This is the same value as an interpolated_delta divided by the duration in seconds.


interpolated_rate(
    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 rate should be computed over (if there is a preceeding point)
`interval`	`INTERVAL`	The length of the interval which the rate 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` will be used as the end of the interval.

Returns

Name	Type	Description
`interpolated_rate`	`DOUBLE PRECISION`	The per-second rate of change of the counter between the specified bounds. If the raw data contains no points calculated at those bounds, the bounding values are linearly interpolated from neighboring `CounterSummaries`.

Sample usage


SELECT
    id,
    bucket,
    interpolated_rate(
        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