The slope of the least squares fit line computed from the adjusted counter values and times input in the CounterSummary. Because the times are input as seconds, the slope provides a per-second rate of change estimate based on the least squares fit, which is often similar to the result of the rate calculation, but can more accurately reflect the usual behavior if there are infrequent, large changes in a counter.
slope( summary CounterSummary ) RETURNS DOUBLE PRECISION
For more information about counter aggregation functions, see the hyperfunctions documentation.
|summary||CounterSummary||The input CounterSummary from a |
|slope||DOUBLE PRECISION||The per second rate of change computed by taking the slope of the least squares fit of the points input in the CounterSummary|
SELECT id, bucket, slope(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
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