KSQL - 相对时间查询 (ANSI SQL)

Question

How can i write a KSQL query on a bigint column that uses relative time?

IE How can i achieve something like this....

SELECT timestamp,value FROM XYZ where timestamp > now() - INTERVAL 5 MINUTES

Where timestamp is a bigint field; milliseconds since epoch.

EDIT: Context. I need these queries to be passed over the network/database savable and we have many queries that get the last 20mins of data from a stream on a BIGINT field.

IE SELECT timestamp from STREAMNAME where timestamp > 1592882020842

The problem with saving/sending this query as more and more time elapses since the point where it was saved therefore moving further and further away from "20mins ago".

What i acutally want is a query like this.

SELECT timestamp from STREAMNAME where timestmap > now() - 20mins

No matter how many times this query is saved/loaded/sent across network/run in future. Will always return the timestamps from 20mins ago -> now

I have since found something in the documentatino that achives what i want UNIX_TIMESTAMP() which returns the time in milliseconds in BIGINT format.

Answer 1

UNIX_TIMESTAMP returns the current wallclock time in milliseconds at the time the row is processed , ie it returns the processing time. The timestamp returned by the function will advance as each row is processed.

This is different to how a traditional database would handle now , which would be evaluated once, and this single immutable timestamp would be used for the duration of the query, regardless of how long the query took to run.

It's important to understand the difference. If UNIX_TIMESTAMP does what you want... then great!