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Add keyword marker token filter docs #8065
Signed-off-by: Anton Rubin <[email protected]>
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| --- | ||
| layout: default | ||
| title: Keyword marker | ||
| parent: Token filters | ||
| nav_order: 200 | ||
| --- | ||
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| # Keyword marker token filter | ||
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| The `keyword_marker` token filter in OpenSearch is used to prevent certain tokens from being altered by stemmers or other filters. This ensures that specific words remain in their original form. `keyword_marker` token filter does this by marking tokens as `keywords` which prevents any stemming or other processing. | ||
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| ## Parameters | ||
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| The `keyword_marker` token filter in OpenSearch can be configured with the following parameters: | ||
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| - `ignore_case`: Ignore the letter case when matching keywords. Default is `false.` (Boolean, _Optional_) | ||
| - `keywords`: List of strings used to match tokens. (List of strings, _Required_ if `keywords_path` or `keywords_pattern` is not set) | ||
| - `keywords_path`: Path (relative to `config` directory or absolute) to list of strings. (String, _Required_ if `keywords` or `keywords_pattern` is not set) | ||
| - `keywords_pattern`: [Regular expression](https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html) used for matching tokens. (String, _Required_ if `keywords` or `keywords_path` is not set) | ||
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| ## Example | ||
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| The following example request creates a new index named `my_index` and configures an analyzer with `keyword_marker` filter: | ||
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| ```json | ||
| PUT /my_index | ||
| { | ||
| "settings": { | ||
| "analysis": { | ||
| "analyzer": { | ||
| "custom_analyzer": { | ||
| "type": "custom", | ||
| "tokenizer": "standard", | ||
| "filter": ["lowercase", "keyword_marker_filter", "stemmer"] | ||
| } | ||
| }, | ||
| "filter": { | ||
| "keyword_marker_filter": { | ||
| "type": "keyword_marker", | ||
| "keywords": ["OpenSearch", "example"] | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| ``` | ||
| {% include copy-curl.html %} | ||
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| ## Generated tokens | ||
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| Use the following request to examine the tokens generated using the created analyzer: | ||
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| ```json | ||
| GET /my_index/_analyze | ||
| { | ||
| "analyzer": "custom_analyzer", | ||
| "text": "This is an OpenSearch example demonstrating keyword marker." | ||
| } | ||
| ``` | ||
| {% include copy-curl.html %} | ||
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| The response contains the generated tokens: | ||
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| ```json | ||
| { | ||
| "tokens": [ | ||
| { | ||
| "token": "thi", | ||
| "start_offset": 0, | ||
| "end_offset": 4, | ||
| "type": "<ALPHANUM>", | ||
| "position": 0 | ||
| }, | ||
| { | ||
| "token": "is", | ||
| "start_offset": 5, | ||
| "end_offset": 7, | ||
| "type": "<ALPHANUM>", | ||
| "position": 1 | ||
| }, | ||
| { | ||
| "token": "an", | ||
| "start_offset": 8, | ||
| "end_offset": 10, | ||
| "type": "<ALPHANUM>", | ||
| "position": 2 | ||
| }, | ||
| { | ||
| "token": "opensearch", | ||
| "start_offset": 11, | ||
| "end_offset": 21, | ||
| "type": "<ALPHANUM>", | ||
| "position": 3 | ||
| }, | ||
| { | ||
| "token": "example", | ||
| "start_offset": 22, | ||
| "end_offset": 29, | ||
| "type": "<ALPHANUM>", | ||
| "position": 4 | ||
| }, | ||
| { | ||
| "token": "demonstr", | ||
| "start_offset": 30, | ||
| "end_offset": 43, | ||
| "type": "<ALPHANUM>", | ||
| "position": 5 | ||
| }, | ||
| { | ||
| "token": "keyword", | ||
| "start_offset": 44, | ||
| "end_offset": 51, | ||
| "type": "<ALPHANUM>", | ||
| "position": 6 | ||
| }, | ||
| { | ||
| "token": "marker", | ||
| "start_offset": 52, | ||
| "end_offset": 58, | ||
| "type": "<ALPHANUM>", | ||
| "position": 7 | ||
| } | ||
| ] | ||
| } | ||
| ``` | ||
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| You can further examine the impact of the `keyword_marker` token filter by adding the following parameters to the `_analyze` query: | ||
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| ```json | ||
| GET /my_index/_analyze | ||
| { | ||
| "analyzer": "custom_analyzer", | ||
| "text": "This is an OpenSearch example demonstrating keyword marker.", | ||
| "explain": true, | ||
| "attributes": "keyword" | ||
| } | ||
| ``` | ||
| {% include copy-curl.html %} | ||
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| This will produce additional details in the response similar to the following: | ||
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| ```json | ||
| { | ||
| "name": "porter_stem", | ||
| "tokens": [ | ||
| ... | ||
| { | ||
| "token": "example", | ||
| "start_offset": 22, | ||
| "end_offset": 29, | ||
| "type": "<ALPHANUM>", | ||
| "position": 4, | ||
| "keyword": true | ||
| }, | ||
| { | ||
| "token": "demonstr", | ||
| "start_offset": 30, | ||
| "end_offset": 43, | ||
| "type": "<ALPHANUM>", | ||
| "position": 5, | ||
| "keyword": false | ||
| }, | ||
| ... | ||
| ] | ||
| } | ||
| ``` |