[DOCS] Reformat lowercase token filter docs (#49935)
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James Rodewig
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[[analysis-lowercase-tokenfilter]]
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=== Lowercase Token Filter
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=== Lowercase token filter
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++++
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<titleabbrev>Lowercase</titleabbrev>
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++++
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A token filter of type `lowercase` that normalizes token text to lower
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case.
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Changes token text to lowercase. For example, you can use the `lowercase` filter
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to change `THE Lazy DoG` to `the lazy dog`.
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Lowercase token filter supports Greek, Irish, and Turkish lowercase token
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filters through the `language` parameter. Below is a usage example in a
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custom analyzer
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In addition to a default filter, the `lowercase` token filter provides access to
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Lucene's language-specific lowercase filters for Greek, Irish, and Turkish.
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[[analysis-lowercase-tokenfilter-analyze-ex]]
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==== Example
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The following <<indices-analyze,analyze API>> request uses the default
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`lowercase` filter to change the `THE Quick FoX JUMPs` to lowercase:
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[source,console]
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--------------------------------------------------
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PUT /lowercase_example
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GET _analyze
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{
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"tokenizer" : "standard",
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"filter" : ["lowercase"],
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"text" : "THE Quick FoX JUMPs"
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}
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--------------------------------------------------
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The filter produces the following tokens:
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[source,text]
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--------------------------------------------------
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[ the, quick, fox, jumps ]
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--------------------------------------------------
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/////////////////////
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[source,console-result]
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--------------------------------------------------
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{
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"tokens" : [
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{
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"token" : "the",
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"start_offset" : 0,
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"end_offset" : 3,
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"type" : "<ALPHANUM>",
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"position" : 0
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},
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{
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"token" : "quick",
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"start_offset" : 4,
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"end_offset" : 9,
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"type" : "<ALPHANUM>",
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"position" : 1
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},
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{
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"token" : "fox",
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"start_offset" : 10,
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"end_offset" : 13,
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"type" : "<ALPHANUM>",
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"position" : 2
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},
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{
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"token" : "jumps",
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"start_offset" : 14,
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"end_offset" : 19,
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"type" : "<ALPHANUM>",
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"position" : 3
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}
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]
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}
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--------------------------------------------------
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/////////////////////
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[[analysis-lowercase-tokenfilter-analyzer-ex]]
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==== Add to an analyzer
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The following <<indices-create-index,create index API>> request uses the
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`lowercase` filter to configure a new
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<<analysis-custom-analyzer,custom analyzer>>.
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[source,console]
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--------------------------------------------------
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PUT lowercase_example
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{
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"settings" : {
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"analysis" : {
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"analyzer" : {
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"whitespace_lowercase" : {
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"tokenizer" : "whitespace",
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"filter" : ["lowercase"]
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}
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}
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}
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}
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}
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--------------------------------------------------
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[[analysis-lowercase-tokenfilter-configure-parms]]
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==== Configurable parameters
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`language`::
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+
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--
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(Optional, string)
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Language-specific lowercase token filter to use. Valid values include:
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`greek`::: Uses Lucene's https://lucene.apache.org/core/{lucene_version_path}/analyzers-common/org/apache/lucene/analysis/el/GreekLowerCaseFilter.html[GreekLowerCaseFilter]
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`irish`::: Uses Lucene's http://lucene.apache.org/core/{lucene_version_path}/analyzers-common/org/apache/lucene/analysis/ga/IrishLowerCaseFilter.html[IrishLowerCaseFilter]
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`turkish`::: Uses Lucene's https://lucene.apache.org/core/{lucene_version_path}/analyzers-common/org/apache/lucene/analysis/tr/TurkishLowerCaseFilter.html[TurkishLowerCaseFilter]
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If not specified, defaults to Lucene's https://lucene.apache.org/core/{lucene_version_path}/analyzers-common/org/apache/lucene/analysis/core/LowerCaseFilter.html[LowerCaseFilter].
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--
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[[analysis-lowercase-tokenfilter-customize]]
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==== Customize
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To customize the `lowercase` filter, duplicate it to create the basis
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for a new custom token filter. You can modify the filter using its configurable
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parameters.
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For example, the following request creates a custom `lowercase` filter for the
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Greek language:
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[source,console]
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--------------------------------------------------
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PUT custom_lowercase_example
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{
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"settings": {
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"analysis": {
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"analyzer": {
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"standard_lowercase_example": {
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"type": "custom",
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"tokenizer": "standard",
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"filter": ["lowercase"]
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},
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"greek_lowercase_example": {
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"type": "custom",
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"tokenizer": "standard",
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