diff --git a/docs/reference/analysis.asciidoc b/docs/reference/analysis.asciidoc index 10a1cc6a89f71..460335a20eb47 100644 --- a/docs/reference/analysis.asciidoc +++ b/docs/reference/analysis.asciidoc @@ -2,6 +2,7 @@ = Text analysis :lucene-analysis-docs: https://lucene.apache.org/core/{lucene_version_path}/analyzers-common/org/apache/lucene/analysis +:lucene-stop-word-link: https://github.com/apache/lucene-solr/blob/master/lucene/analysis/common/src/resources/org/apache/lucene/analysis [partintro] -- diff --git a/docs/reference/analysis/tokenfilters/stop-tokenfilter.asciidoc b/docs/reference/analysis/tokenfilters/stop-tokenfilter.asciidoc index 3263d89e2b3ff..0e7a53f6a6980 100644 --- a/docs/reference/analysis/tokenfilters/stop-tokenfilter.asciidoc +++ b/docs/reference/analysis/tokenfilters/stop-tokenfilter.asciidoc @@ -4,79 +4,374 @@ Stop ++++ -A token filter of type `stop` that removes stop words from token -streams. +Removes https://en.wikipedia.org/wiki/Stop_words[stop words] from a token +stream. -The following are settings that can be set for a `stop` token filter -type: +When not customized, the filter removes the following English stop words by +default: + +`a`, `an`, `and`, `are`, `as`, `at`, `be`, `but`, `by`, `for`, `if`, `in`, +`into`, `is`, `it`, `no`, `not`, `of`, `on`, `or`, `such`, `that`, `the`, +`their`, `then`, `there`, `these`, `they`, `this`, `to`, `was`, `will`, `with` + +In addition to English, the `stop` filter supports predefined +<>. You can also specify your own stop words as an array or file. + +The `stop` filter uses Lucene's +{lucene-analysis-docs}/StopFilter.html[StopFilter]. + +[[analysis-stop-tokenfilter-analyze-ex]] +==== Example + +The following analyze API request uses the `stop` filter to remove the stop words +`a` and `the` from `a quick fox jumps over the lazy dog`: + +[source,console] +---- +GET /_analyze +{ + "tokenizer": "standard", + "filter": [ "stop" ], + "text": "a quick fox jumps over the lazy dog" +} +---- + +The filter produces the following tokens: + +[source,text] +---- +[ quick, fox, jumps, over, lazy, dog ] +---- + +//// +[source,console-result] +---- +{ + "tokens": [ + { + "token": "quick", + "start_offset": 2, + "end_offset": 7, + "type": "", + "position": 1 + }, + { + "token": "fox", + "start_offset": 8, + "end_offset": 11, + "type": "", + "position": 2 + }, + { + "token": "jumps", + "start_offset": 12, + "end_offset": 17, + "type": "", + "position": 3 + }, + { + "token": "over", + "start_offset": 18, + "end_offset": 22, + "type": "", + "position": 4 + }, + { + "token": "lazy", + "start_offset": 27, + "end_offset": 31, + "type": "", + "position": 6 + }, + { + "token": "dog", + "start_offset": 32, + "end_offset": 35, + "type": "", + "position": 7 + } + ] +} +---- +//// + +[[analysis-stop-tokenfilter-analyzer-ex]] +==== Add to an analyzer + +The following <> request uses the `stop` +filter to configure a new <>. + +[source,console] +---- +PUT /my_index +{ + "settings": { + "analysis": { + "analyzer": { + "my_analyzer": { + "tokenizer": "whitespace", + "filter": [ "stop" ] + } + } + } + } +} +---- + +[[analysis-stop-tokenfilter-configure-parms]] +==== Configurable parameters -[horizontal] `stopwords`:: ++ +-- +(Optional, string or array of strings) +Language value, such as `_arabic_` or `_thai_`. Defaults to +<>. - A list of stop words to use. Defaults to `_english_` stop words. +Each language value corresponds to a predefined list of stop words in Lucene. +See <> for supported language +values and their stop words. + +Also accepts an array of stop words. + +For an empty list of stop words, use `_none_`. +-- `stopwords_path`:: ++ +-- +(Optional, string) +Path to a file that contains a list of stop words to remove. - A path (either relative to `config` location, or absolute) to a stopwords - file configuration. Each stop word should be in its own "line" (separated - by a line break). The file must be UTF-8 encoded. +This path must be absolute or relative to the `config` location, and the file +must be UTF-8 encoded. Each stop word in the file must be separated by a line +break. +-- `ignore_case`:: - - Set to `true` to lower case all words first. Defaults to `false`. +(Optional, boolean) +If `true`, stop word matching is case insensitive. For example, if `true`, a +stop word of `the` matches and removes `The`, `THE`, or `the`. Defaults to +`false`. `remove_trailing`:: ++ +-- +(Optional, boolean) +If `true`, the last token of a stream is removed if it's a stop word. Defaults +to `true`. + +This parameter should be `false` when using the filter with a +<>. This would ensure a query like +`green a` matches and suggests `green apple` while still removing other stop +words. +-- - Set to `false` in order to not ignore the last term of a search if it is a - stop word. This is very useful for the completion suggester as a query - like `green a` can be extended to `green apple` even though you remove - stop words in general. Defaults to `true`. +[[analysis-stop-tokenfilter-customize]] +==== Customize -The `stopwords` parameter accepts either an array of stopwords: +To customize the `stop` filter, duplicate it to create the basis +for a new custom token filter. You can modify the filter using its configurable +parameters. + +For example, the following request creates a custom case-insensitive `stop` +filter that removes stop words from the <> stop +words list: [source,console] ------------------------------------- +---- PUT /my_index { - "settings": { - "analysis": { - "filter": { - "my_stop": { - "type": "stop", - "stopwords": ["and", "is", "the"] - } - } + "settings": { + "analysis": { + "analyzer": { + "default": { + "tokenizer": "whitespace", + "filter": [ "my_custom_stop_words_filter" ] + } + }, + "filter": { + "my_custom_stop_words_filter": { + "type": "stop", + "ignore_case": true } + } } + } } ------------------------------------- +---- -or a predefined language-specific list: +You can also specify your own list of stop words. For example, the following +request creates a custom case-sensitive `stop` filter that removes only the stop +words `and`, `is`, and `the`: [source,console] ------------------------------------- +---- PUT /my_index { - "settings": { - "analysis": { - "filter": { - "my_stop": { - "type": "stop", - "stopwords": "_english_" - } - } + "settings": { + "analysis": { + "analyzer": { + "default": { + "tokenizer": "whitespace", + "filter": [ "my_custom_stop_words_filter" ] } + }, + "filter": { + "my_custom_stop_words_filter": { + "type": "stop", + "ignore_case": true, + "stopwords": [ "and", "is", "the" ] + } + } } + } } ------------------------------------- +---- + +[[analysis-stop-tokenfilter-stop-words-by-lang]] +==== Stop words by language + +The following list contains supported language values for the `stopwords` +parameter and a link to their predefined stop words in Lucene. + +[[arabic-stop-words]] +`_arabic_`:: +{lucene-stop-word-link}/ar/stopwords.txt[Arabic stop words] + +[[armenian-stop-words]] +`_armenian_`:: +{lucene-stop-word-link}/hy/stopwords.txt[Armenian stop words] + +[[basque-stop-words]] +`_basque_`:: +{lucene-stop-word-link}/eu/stopwords.txt[Basque stop words] + +[[bengali-stop-words]] +`_bengali_`:: +{lucene-stop-word-link}/bn/stopwords.txt[Bengali stop words] + +[[brazilian-stop-words]] +`_brazilian_` (Brazilian Portuguese):: +{lucene-stop-word-link}/br/stopwords.txt[Brazilian Portuguese stop words] + +[[bulgarian-stop-words]] +`_bulgarian_`:: +{lucene-stop-word-link}/bg/stopwords.txt[Bulgarian stop words] + +[[catalan-stop-words]] +`_catalan_`:: +{lucene-stop-word-link}/ca/stopwords.txt[Catalan stop words] + +[[cjk-stop-words]] +`_cjk_` (Chinese, Japanese, and Korean):: +{lucene-stop-word-link}/cjk/stopwords.txt[CJK stop words] + +[[czech-stop-words]] +`_czech_`:: +{lucene-stop-word-link}/cz/stopwords.txt[Czech stop words] + +[[danish-stop-words]] +`_danish_`:: +{lucene-stop-word-link}/snowball/danish_stop.txt[Danish stop words] + +[[dutch-stop-words]] +`_dutch_`:: +{lucene-stop-word-link}/snowball/dutch_stop.txt[Dutch stop words] + +[[english-stop-words]] +`_english_`:: +https://github.com/apache/lucene-solr/blob/master/lucene/analysis/common/src/java/org/apache/lucene/analysis/en/EnglishAnalyzer.java#L46[English stop words] + +[[estonian-stop-words]] +`_estonian_`:: +https://github.com/apache/lucene-solr/blob/master/lucene/analysis/common/src/resources/org/apache/lucene/analysis/et/stopwords.txt[Estonian stop words] + +[[finnish-stop-words]] +`_finnish_`:: +{lucene-stop-word-link}/snowball/finnish_stop.txt[Finnish stop words] + +[[french-stop-words]] +`_french_`:: +{lucene-stop-word-link}/snowball/french_stop.txt[French stop words] + +[[galician-stop-words]] +`_galician_`:: +{lucene-stop-word-link}/gl/stopwords.txt[Galician stop words] + +[[german-stop-words]] +`_german_`:: +{lucene-stop-word-link}/snowball/german_stop.txt[German stop words] + +[[greek-stop-words]] +`_greek_`:: +{lucene-stop-word-link}/el/stopwords.txt[Greek stop words] + +[[hindi-stop-words]] +`_hindi_`:: +{lucene-stop-word-link}/hi/stopwords.txt[Hindi stop words] + +[[hungarian-stop-words]] +`_hungarian_`:: +{lucene-stop-word-link}/snowball/hungarian_stop.txt[Hungarian stop words] + +[[indonesian-stop-words]] +`_indonesian_`:: +{lucene-stop-word-link}/id/stopwords.txt[Indonesian stop words] + +[[irish-stop-words]] +`_irish_`:: +{lucene-stop-word-link}/ga/stopwords.txt[Irish stop words] + +[[italian-stop-words]] +`_italian_`:: +{lucene-stop-word-link}/snowball/italian_stop.txt[Italian stop words] + +[[latvian-stop-words]] +`_latvian_`:: +{lucene-stop-word-link}/lv/stopwords.txt[Latvian stop words] + +[[lithuanian-stop-words]] +`_lithuanian_`:: +{lucene-stop-word-link}/lt/stopwords.txt[Lithuanian stop words] + +[[norwegian-stop-words]] +`_norwegian_`:: +{lucene-stop-word-link}/snowball/norwegian_stop.txt[Norwegian stop words] + +[[persian-stop-words]] +`_persian_`:: +{lucene-stop-word-link}/fa/stopwords.txt[Persian stop words] + +[[portuguese-stop-words]] +`_portuguese_`:: +{lucene-stop-word-link}/snowball/portuguese_stop.txt[Portuguese stop words] + +[[romanian-stop-words]] +`_romanian_`:: +{lucene-stop-word-link}/ro/stopwords.txt[Romanian stop words] + +[[russian-stop-words]] +`_russian_`:: +{lucene-stop-word-link}/snowball/russian_stop.txt[Russian stop words] + +[[sorani-stop-words]] +`_sorani_`:: +{lucene-stop-word-link}/ckb/stopwords.txt[Sorani stop words] + +[[spanish-stop-words]] +`_spanish_`:: +{lucene-stop-word-link}/snowball/spanish_stop.txt[Spanish stop words] -Elasticsearch provides the following predefined list of languages: +[[swedish-stop-words]] +`_swedish_`:: +{lucene-stop-word-link}/snowball/swedish_stop.txt[Swedish stop words] -`_arabic_`, `_armenian_`, `_basque_`, `_bengali_`, `_brazilian_`, `_bulgarian_`, -`_catalan_`, `_czech_`, `_danish_`, `_dutch_`, `_english_`, `_estonian_`, `_finnish_`, -`_french_`, `_galician_`, `_german_`, `_greek_`, `_hindi_`, `_hungarian_`, -`_indonesian_`, `_irish_`, `_italian_`, `_latvian_`, `_norwegian_`, `_persian_`, -`_portuguese_`, `_romanian_`, `_russian_`, `_sorani_`, `_spanish_`, -`_swedish_`, `_thai_`, `_turkish_`. +[[thai-stop-words]] +`_thai_`:: +{lucene-stop-word-link}/th/stopwords.txt[Thai stop words] -For the empty stopwords list (to disable stopwords) use: `_none_`. +[[turkish-stop-words]] +`_turkish_`:: +{lucene-stop-word-link}/tr/stopwords.txt[Turkish stop words] \ No newline at end of file