first_val()

Get the first value from a TimeWeightSummary aggregate

Since 1.11.0

Get the value of the first point in a TimeWeightSummary aggregate.

Samples

Produce a linear TimeWeightSummary over the column val and get the first value:

WITH t as (
    SELECT
        time_bucket('1 day'::interval, ts) as dt,
        time_weight('Linear', ts, val) AS tw
    FROM table
    GROUP BY time_bucket('1 day'::interval, ts)
)
SELECT
    dt,
    first_val(tw)
FROM t;

Arguments

The syntax is:

first_val(
    tw TimeWeightSummary
) RETURNS DOUBLE PRECISION

Name	Type	Default	Required	Description
tws	TimeWeightSummary	-	✔	The input TimeWeightSummary from a time_weight() call

Returns

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