# Very slow performance of must\_not with exists in filter
**URL:** https://discuss.elastic.co/t/very-slow-performance-of-must-not-with-exists-in-filter/144281
**Category:** Elasticsearch
**Created:** [August 14, 2018, 6:37am UTC](https://discuss.elastic.co/t/very-slow-performance-of-must-not-with-exists-in-filter/144281 "2018-08-14T06:37:06Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@ShilpiRachna](https://discuss.elastic.co/u/ShilpiRachna)
#### Post date: [August 14, 2018, 6:37am UTC](https://discuss.elastic.co/t/very-slow-performance-of-must-not-with-exists-in-filter/144281/1 "2018-08-14T06:37:06Z")
Hi,
We are investigating some slow queries in our Prod environment. We saw that the following filter is much slower than other term queries in query / filter section.
"query": {
"bool": {
"must": {…},
"filter" : {
"should": [
{
"bool": {
"must\_not": [
{
"exists": {
"field": "isDiscussionOnly"
}
}
]
}
},
{
"terms": {
"isDiscussionOnly": [
"false"
]
}
}
]
}
}
}
Is there any known performance issue / performance guideline around using must\_not with exists.
Would it help to always have this field set (with some default value) and replace the above filter with term query filter?
---
### Author:  [@jaddison](https://discuss.elastic.co/u/jaddison)
#### Post date: [September 9, 2018, 9:22pm UTC](https://discuss.elastic.co/t/very-slow-performance-of-must-not-with-exists-in-filter/144281/2 "2018-09-09T21:22:49Z")
If you format/indent your code, it makes it easier for people to answer.
Perhaps the discussion in this [Github issue](https://github.com/elastic/elasticsearch/issues/22657) would be helpful?
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [October 7, 2018, 9:22pm UTC](https://discuss.elastic.co/t/very-slow-performance-of-must-not-with-exists-in-filter/144281/3 "2018-10-07T21:22:50Z")
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