RANGE PRECEDING is only supported with UNBOUNDED

问题

I want to try avg() aggregation within a time window sql code

select
user_id,timestamp
avg(y) over(range between '5 second' preceding and '5 second' following),
from A

but the system report error

RANGE PRECEDING is only supported with UNBOUNDED

Is there any method to implement, say, a 10 second window for avg() window function?

frame of window function is as wide as range from n seconds preceding the timestamp of current row and m seconds following the timestamp of current row

回答1:

 RANGE PRECEDING is only supported with UNBOUNDED

Yep ... PostgreSQL's window functions don't yet implement ranges.

I've had many situations where they would've been useful, but it's a lot of work to implement them and time is limited.

Is there any method to implement, say, a 10 second window for avg() window function?

You will need to use a left join over generate_series (and, if appropriate, aggregation) to turn the range into a regular sequence of rows, inserting null rows where there's no data, and combining multiple data from within one second to a single value where there are multiple values.

Then you do a (ROWS n PRECEDING ...) window over the left-joined and aggregated data to get the running average.

来源：https://stackoverflow.com/questions/26791167/range-preceding-is-only-supported-with-unbounded