# Using a must\_not filter on 'drone' returns a document containing 'drone' **URL:** \ **Category:** Elasticsearch\ **Created:** [September 26, 2022, 9:06am UTC](https://discuss.elastic.co/t/using-a-must-not-filter-on-drone-returns-a-document-containing-drone/315150 "2022-09-26T09:06:40Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![cracanut](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/cracanut/32/107727_2.png) [@cracanut](https://discuss.elastic.co/u/cracanut)\ **Post date:** [September 26, 2022, 9:06am UTC](https://discuss.elastic.co/t/using-a-must-not-filter-on-drone-returns-a-document-containing-drone/315150/1 "2022-09-26T09:06:40Z")
Using a must\_not filter on 'drone' returns a document containing 'drone': Cluster analyzer settings: ```auto "analysis": { "filter": { "english_stemmer": { "type": "stemmer", "language": "english" }, "english_possessive_stemmer": { "type": "stemmer", "language": "possessive_english" } }, "analyzer": { "eng_stemmer": { "tokenizer": "whitespace", "char_filter": ["html_strip", "custom_char_filter_start_of_word", "custom_char_filter_end_of_word"], "filter": [ "english_possessive_stemmer", "lowercase", "english_stemmer" ] } }, "char_filter": { "custom_char_filter_end_of_word": { "type": "pattern_replace", "pattern": "[\\W]+(\\s|$)", "replacement": " " }, "custom_char_filter_start_of_word": { "type": "pattern_replace", "pattern": "(\\s|^)[\\W]+", "replacement": " " } } } ``` When using this query: ```auto { "query": { "bool":{ "must_not": [ { "match": { "title": "drone" } } ], "must": [ { "match": { "title": "wing" } } ] } } } ``` I get a document with the following title in my results: ```auto "title": "Hydrodynamic or streamlined profile for forming e.g. drone`s wing, has core comprising active section deformed under effect of variation of temperature of active layer inducing amplitude and direction deformation in zones of envelope", ``` I tried the /\_analyze for both the search term and the title and both are stemmed to 'drone', yet the document is not filtered out of the result. Am I missing something or is this a bug? ---
**Author:** ![dadoonet](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dadoonet/32/137187_2.png) [@dadoonet](https://discuss.elastic.co/u/dadoonet)\ **Post date:** [September 26, 2022, 10:11am UTC](https://discuss.elastic.co/t/using-a-must-not-filter-on-drone-returns-a-document-containing-drone/315150/2 "2022-09-26T10:11:29Z")
What is the mapping for the field `title`? Is "drone`s" really analyzed as `drone`? Could you share the output of: ```auto GET /INDEX/_analyze { "field" : "title", "text" : Hydrodynamic or streamlined profile for forming e.g. drone`s wing, has core comprising active section deformed under effect of variation of temperature of active layer inducing amplitude and direction deformation in zones of envelope" } ``` ---
**Author:** ![cracanut](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/cracanut/32/107727_2.png) [@cracanut](https://discuss.elastic.co/u/cracanut)\ **Post date:** [September 26, 2022, 10:23am UTC](https://discuss.elastic.co/t/using-a-must-not-filter-on-drone-returns-a-document-containing-drone/315150/3 "2022-09-26T10:23:57Z")
Thank you for the reply. The title field uses the 'eng\_stemmer' analyzer. I just redid the \_analyze and found the issue (I must have overlooked it earlier): > drone's is reduced to > drone' (notice the single quote not being removed). I expected the 'english\_stemmer' or 'english\_possessive\_stemmer' to remove the quote as well as this is a regular occurence in the English language? Edit: perhaps it's because it doesn't appear to be a standard single quote? ---
**Author:** ![dadoonet](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dadoonet/32/137187_2.png) [@dadoonet](https://discuss.elastic.co/u/dadoonet)\ **Post date:** [September 26, 2022, 10:39am UTC](https://discuss.elastic.co/t/using-a-must-not-filter-on-drone-returns-a-document-containing-drone/315150/4 "2022-09-26T10:39:33Z")
So that's the reason when searching for `drone` it can not match with "drone'"... Instead of using a `whitespace` tokenizer, I'd use the `standard` one. Could you check that? ---
**Author:** ![cracanut](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/cracanut/32/107727_2.png) [@cracanut](https://discuss.elastic.co/u/cracanut)\ **Post date:** [September 26, 2022, 10:59am UTC](https://discuss.elastic.co/t/using-a-must-not-filter-on-drone-returns-a-document-containing-drone/315150/5 "2022-09-26T10:59:17Z")
We can't use the standard tokenizer. We need to do a search on e.g. match "C/C" but the standard tokenizer removes the forward slash resulting in documents with "c c" in the result. ---
**Author:** ![dadoonet](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dadoonet/32/137187_2.png) [@dadoonet](https://discuss.elastic.co/u/dadoonet)\ **Post date:** [September 26, 2022, 11:53am UTC](https://discuss.elastic.co/t/using-a-must-not-filter-on-drone-returns-a-document-containing-drone/315150/6 "2022-09-26T11:53:15Z")
I checked the documentation and the `standard` tokenizer won't work I think anyway. May be look at > **[Character group tokenizer | Elasticsearch Guide \[8.4\] | Elastic](https://www.elastic.co/guide/en/elasticsearch/reference/current/analysis-chargroup-tokenizer.html)** ---
**Author:** ![cracanut](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/cracanut/32/107727_2.png) [@cracanut](https://discuss.elastic.co/u/cracanut)\ **Post date:** [September 26, 2022, 3:03pm UTC](https://discuss.elastic.co/t/using-a-must-not-filter-on-drone-returns-a-document-containing-drone/315150/7 "2022-09-26T15:03:26Z")
Looks like replacing every > ` with a standard single quote (using a mapping char filter) seems to be working. "drone`s" is now correctly stemmed to "drone". ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [October 24, 2022, 3:04pm UTC](https://discuss.elastic.co/t/using-a-must-not-filter-on-drone-returns-a-document-containing-drone/315150/8 "2022-10-24T15:04:12Z")
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