# How should I format a post\_filter query to match a string inside of a string?
**URL:** https://discuss.elastic.co/t/how-should-i-format-a-post-filter-query-to-match-a-string-inside-of-a-string/107464
**Category:** Elasticsearch
**Created:** [November 13, 2017, 9:14pm UTC](https://discuss.elastic.co/t/how-should-i-format-a-post-filter-query-to-match-a-string-inside-of-a-string/107464 "2017-11-13T21:14:30Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@simonstiph](https://discuss.elastic.co/u/simonstiph)
#### Post date: [November 13, 2017, 9:14pm UTC](https://discuss.elastic.co/t/how-should-i-format-a-post-filter-query-to-match-a-string-inside-of-a-string/107464/1 "2017-11-13T21:14:30Z")
I have an array of articles (i.e. from newspapers) in a MongoDB database that is indexed into Elasticsearch. Each article has any number of authors, like: ['John Doe', 'Jane Doe'].
In Es, I have aggregation by author working properly, but I also want to apply a post\_filter to filter results by author. How should a post\_filter query be designed to handle this?
Article schema in Es (can be modified if necessary):
```
{
...
authors: ['Michael Jordan', 'Kobe Bryant'],
authorsString: 'Michael Jordan;Kobe Bryant;'
}
```
This is an example query before applying the post\_filter:
```
{
...
aggs: {
authors: {
terms: {
field: 'authors.keyword',
},
},
},
post_filter: {},
}
```
If I want to find articles of which at least one of the authors is "Michael Jordan", how do I use post\_filter to do so?
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [December 11, 2017, 9:14pm UTC](https://discuss.elastic.co/t/how-should-i-format-a-post-filter-query-to-match-a-string-inside-of-a-string/107464/2 "2017-12-11T21:14:32Z")
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