follow¶
Type of operation: Join
Description¶
Return the rows from the additional joined dataset that have a match anywhere in the query time window.
follow performs a non-temporal semijoin. The join will select any rows from the first dataset that have at least one matching row in the second dataset.
Usage¶
follow [ frame ], predicate_1, predicate_2, ...
Argument |
Type |
Optional |
Repeatable |
Restrictions |
|---|---|---|---|---|
frame |
frame |
yes |
no |
constant |
predicate |
bool |
no |
yes |
none |
Accelerable¶
follow is accelerable if there is a frame() argument. A dataset that only uses accelerable verbs can be accelerated, making queries on the dataset respond faster.
Examples¶
follow [email protected]_id
Semijoin the default dataset with the ‘right’ dataset, returning rows from ‘right’ where there exists a key match at any point in time within the query window.
follow frame(back:30m), [email protected]_id
Semijoin the default dataset with the ‘right’ dataset, returning rows from ‘right’ where there exists a key match within 30 minutes in time.
follow [email protected]_id and sensor_value>@right.sensor_value
Semijoin the default dataset with the ‘right’ dataset, returning rows from ‘right’ whose sensor_value is less than the value from the default dataset for the same sensor_id at any point in time within the query window.