# How can I check index exists in logstash filter and how can get dynamic field from elasticsearch lookup( in filter plugin)

**URL:** <https://discuss.elastic.co/t/how-can-i-check-index-exists-in-logstash-filter-and-how-can-get-dynamic-field-from-elasticsearch-lookup-in-filter-plugin/147616>\
**Category:** Logstash\
**Created:** [September 6, 2018, 5:25pm UTC](https://discuss.elastic.co/t/how-can-i-check-index-exists-in-logstash-filter-and-how-can-get-dynamic-field-from-elasticsearch-lookup-in-filter-plugin/147616 "2018-09-06T17:25:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jam1142](https://avatars.discourse-cdn.com/v4/letter/j/b2d939/32.png) [@jam1142](https://discuss.elastic.co/u/jam1142)\
**Post date:** [September 6, 2018, 5:25pm UTC](https://discuss.elastic.co/t/how-can-i-check-index-exists-in-logstash-filter-and-how-can-get-dynamic-field-from-elasticsearch-lookup-in-filter-plugin/147616/1 "2018-09-06T17:25:07Z")

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Q1:

How can i check index exists in "Elasticsearch filter plugin". My situation is taht i am getting old data from elasticsearch to subtract from current record but in case if that index doesn't exist then i want to subtract 0. Currently Its throwing error if index doesn't exist. I need to know how can i check if index exist in elasticsearch filter so i can handle it.

Q2: Is there a way to do get filter lookup field by dynamic name like

elasticsearch {

hosts =\> "localhost:9200"

index =\> "ptc-db-perfhealth-baseline2"

query\_template =\> "tmp-aggs.json"

fields =\> {

"[stats %{[cntrName]}]" =\> "[@metadata][stats]"

}

}

for me its not working. I know this syntax works for add\_field

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [October 4, 2018, 5:25pm UTC](https://discuss.elastic.co/t/how-can-i-check-index-exists-in-logstash-filter-and-how-can-get-dynamic-field-from-elasticsearch-lookup-in-filter-plugin/147616/2 "2018-10-04T17:25:08Z")

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