|
| 1 | +--- |
| 2 | +layout: default |
| 3 | +title: Keyword marker |
| 4 | +parent: Token filters |
| 5 | +nav_order: 200 |
| 6 | +--- |
| 7 | + |
| 8 | +# Keyword marker token filter |
| 9 | + |
| 10 | +The `keyword_marker` token filter is used to prevent certain tokens from being altered by stemmers or other filters. The `keyword_marker` token filter does this by marking the specified tokens as `keywords`, which prevents any stemming or other processing. This ensures that specific words remain in their original form. |
| 11 | + |
| 12 | +## Parameters |
| 13 | + |
| 14 | +The `keyword_marker` token filter can be configured with the following parameters. |
| 15 | + |
| 16 | +Parameter | Required/Optional | Data type | Description |
| 17 | +:--- | :--- | :--- | :--- |
| 18 | +`ignore_case` | Optional | Boolean | Whether to ignore the letter case when matching keywords. Default is `false`. |
| 19 | +`keywords` | Required if either `keywords_path` or `keywords_pattern` is not set | List of strings | The list of tokens to mark as keywords. |
| 20 | +`keywords_path` | Required if either `keywords` or `keywords_pattern` is not set | String | The path (relative to the `config` directory or absolute) to the list of keywords. |
| 21 | +`keywords_pattern` | Required if either `keywords` or `keywords_path` is not set | String | A [regular expression](https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html) used for matching tokens to be marked as keywords. |
| 22 | + |
| 23 | + |
| 24 | +## Example |
| 25 | + |
| 26 | +The following example request creates a new index named `my_index` and configures an analyzer with a `keyword_marker` filter. The filter marks the word `example` as a keyword: |
| 27 | + |
| 28 | +```json |
| 29 | +PUT /my_index |
| 30 | +{ |
| 31 | + "settings": { |
| 32 | + "analysis": { |
| 33 | + "analyzer": { |
| 34 | + "custom_analyzer": { |
| 35 | + "type": "custom", |
| 36 | + "tokenizer": "standard", |
| 37 | + "filter": ["lowercase", "keyword_marker_filter", "stemmer"] |
| 38 | + } |
| 39 | + }, |
| 40 | + "filter": { |
| 41 | + "keyword_marker_filter": { |
| 42 | + "type": "keyword_marker", |
| 43 | + "keywords": ["example"] |
| 44 | + } |
| 45 | + } |
| 46 | + } |
| 47 | + } |
| 48 | +} |
| 49 | +``` |
| 50 | +{% include copy-curl.html %} |
| 51 | + |
| 52 | +## Generated tokens |
| 53 | + |
| 54 | +Use the following request to examine the tokens generated using the analyzer: |
| 55 | + |
| 56 | +```json |
| 57 | +GET /my_index/_analyze |
| 58 | +{ |
| 59 | + "analyzer": "custom_analyzer", |
| 60 | + "text": "Favorite example" |
| 61 | +} |
| 62 | +``` |
| 63 | +{% include copy-curl.html %} |
| 64 | + |
| 65 | +The response contains the generated tokens. Note that while the word `favorite` was stemmed, the word `example` was not stemmed because it was marked as a keyword: |
| 66 | + |
| 67 | +```json |
| 68 | +{ |
| 69 | + "tokens": [ |
| 70 | + { |
| 71 | + "token": "favorit", |
| 72 | + "start_offset": 0, |
| 73 | + "end_offset": 8, |
| 74 | + "type": "<ALPHANUM>", |
| 75 | + "position": 0 |
| 76 | + }, |
| 77 | + { |
| 78 | + "token": "example", |
| 79 | + "start_offset": 9, |
| 80 | + "end_offset": 16, |
| 81 | + "type": "<ALPHANUM>", |
| 82 | + "position": 1 |
| 83 | + } |
| 84 | + ] |
| 85 | +} |
| 86 | +``` |
| 87 | + |
| 88 | +You can further examine the impact of the `keyword_marker` token filter by adding the following parameters to the `_analyze` query: |
| 89 | + |
| 90 | +```json |
| 91 | +GET /my_index/_analyze |
| 92 | +{ |
| 93 | + "analyzer": "custom_analyzer", |
| 94 | + "text": "This is an OpenSearch example demonstrating keyword marker.", |
| 95 | + "explain": true, |
| 96 | + "attributes": "keyword" |
| 97 | +} |
| 98 | +``` |
| 99 | +{% include copy-curl.html %} |
| 100 | + |
| 101 | +This will produce additional details in the response similar to the following: |
| 102 | + |
| 103 | +```json |
| 104 | +{ |
| 105 | + "name": "porter_stem", |
| 106 | + "tokens": [ |
| 107 | + ... |
| 108 | + { |
| 109 | + "token": "example", |
| 110 | + "start_offset": 22, |
| 111 | + "end_offset": 29, |
| 112 | + "type": "<ALPHANUM>", |
| 113 | + "position": 4, |
| 114 | + "keyword": true |
| 115 | + }, |
| 116 | + { |
| 117 | + "token": "demonstr", |
| 118 | + "start_offset": 30, |
| 119 | + "end_offset": 43, |
| 120 | + "type": "<ALPHANUM>", |
| 121 | + "position": 5, |
| 122 | + "keyword": false |
| 123 | + }, |
| 124 | + ... |
| 125 | + ] |
| 126 | +} |
| 127 | +``` |
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