# Logical expression in pipeline
**URL:** https://discuss.elastic.co/t/logical-expression-in-pipeline/112621
**Category:** Logstash
**Created:** [December 20, 2017, 11:17am UTC](https://discuss.elastic.co/t/logical-expression-in-pipeline/112621 "2017-12-20T11:17:17Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@bodi4](https://discuss.elastic.co/u/bodi4)
#### Post date: [December 20, 2017, 11:17am UTC](https://discuss.elastic.co/t/logical-expression-in-pipeline/112621/1 "2017-12-20T11:17:17Z")
Hi
could someone explain logical expression in pipeline? The case is, for example Output section:
output {
if "C" in [tags] and [filed\_A] = A or "C" in [tags] and [filed\_B] = B
elasticsearch {}
}
Second match group doesn't work. Logstash won't catch event.
What would be right syntax to use matching in tags and fields?
---
### Author:  [@magnusbaeck](https://discuss.elastic.co/u/magnusbaeck)
#### Post date: [December 20, 2017, 11:22am UTC](https://discuss.elastic.co/t/logical-expression-in-pipeline/112621/2 "2017-12-20T11:22:35Z")
The equality operator is `==`, not `=`.
[https://www.elastic.co/guide/en/logstash/current/event-dependent-configuration.html#conditionals](https://www.elastic.co/guide/en/logstash/current/event-dependent-configuration.html#conditionals)
---
### Author:  [@bodi4](https://discuss.elastic.co/u/bodi4)
#### Post date: [December 20, 2017, 11:38am UTC](https://discuss.elastic.co/t/logical-expression-in-pipeline/112621/3 "2017-12-20T11:38:07Z")
My bad.
I'm using == But it doesn't solve problem.
Event won't go to specified index.
Even more, if using
"C" in [tags]
more that 1 time in expression, the whole expression doesn't work.
So, do I have to use several elseif constructions with the same elasticsearch output configuration?
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [January 17, 2018, 11:38am UTC](https://discuss.elastic.co/t/logical-expression-in-pipeline/112621/4 "2018-01-17T11:38:16Z")
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