assert

Drops events and emits a warning if the invariant is violated.

assert invariant:bool

Description

The assert operator asserts that invariant is true for events. In case an event does not satisfy the invariant, it is dropped and a warning is emitted.

Consider using where instead

If you only want to filter events, use where instead of assert. The where operator does not emit a warning when the expression evaluates to false, hence it is more suitable for normal filtering purposes. It is also much faster than assert in some situations due to optimizations such as predicate pushdown.

Examples

Make sure that x != 2

from {x: 1}, {x: 2}, {x: 3}
assert x != 2

{x: 1}
// warning: assertion failure
{x: 3}

Check that a topic only contains certain events

subscribe "network"
assert @name == "ocsf.network_activity"
// continue processing

See Also

assert_throughput, where