247 lines
7.8 KiB
Plaintext
247 lines
7.8 KiB
Plaintext
[[analysis-icu-plugin]]
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== ICU Analysis Plugin
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The http://icu-project.org/[ICU] analysis plugin allows for unicode
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normalization, collation and folding. The plugin is called
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https://github.com/elasticsearch/elasticsearch-analysis-icu[elasticsearch-analysis-icu].
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The plugin includes the following analysis components:
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[float]
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[[icu-normalization]]
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=== ICU Normalization
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Normalizes characters as explained
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http://userguide.icu-project.org/transforms/normalization[here]. It
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registers itself by default under `icu_normalizer` or `icuNormalizer`
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using the default settings. Allows for the name parameter to be provided
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which can include the following values: `nfc`, `nfkc`, and `nfkc_cf`.
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Here is a sample settings:
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[source,js]
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--------------------------------------------------
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{
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"index" : {
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"analysis" : {
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"analyzer" : {
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"normalization" : {
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"tokenizer" : "keyword",
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"filter" : ["icu_normalizer"]
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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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[float]
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[[icu-folding]]
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=== ICU Folding
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Folding of unicode characters based on `UTR#30`. It registers itself
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under `icu_folding` and `icuFolding` names.
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The filter also does lowercasing, which means the lowercase filter can
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normally be left out. Sample setting:
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[source,js]
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--------------------------------------------------
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{
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"index" : {
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"analysis" : {
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"analyzer" : {
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"folding" : {
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"tokenizer" : "keyword",
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"filter" : ["icu_folding"]
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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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[float]
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[[icu-filtering]]
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==== Filtering
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The folding can be filtered by a set of unicode characters with the
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parameter `unicodeSetFilter`. This is useful for a non-internationalized
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search engine where retaining a set of national characters which are
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primary letters in a specific language is wanted. See syntax for the
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UnicodeSet
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http://icu-project.org/apiref/icu4j/com/ibm/icu/text/UnicodeSet.html[here].
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The Following example exempts Swedish characters from the folding. Note
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that the filtered characters are NOT lowercased which is why we add that
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filter below.
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[source,js]
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--------------------------------------------------
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{
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"index" : {
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"analysis" : {
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"analyzer" : {
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"folding" : {
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"tokenizer" : "standard",
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"filter" : ["my_icu_folding", "lowercase"]
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}
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}
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"filter" : {
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"my_icu_folding" : {
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"type" : "icu_folding"
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"unicodeSetFilter" : "[^åäöÅÄÖ]"
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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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[float]
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[[icu-collation]]
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=== ICU Collation
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Uses collation token filter. Allows to either specify the rules for
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collation (defined
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http://www.icu-project.org/userguide/Collate_Customization.html[here])
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using the `rules` parameter (can point to a location or expressed in the
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settings, location can be relative to config location), or using the
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`language` parameter (further specialized by country and variant). By
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default registers under `icu_collation` or `icuCollation` and uses the
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default locale.
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Here is a sample settings:
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[source,js]
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--------------------------------------------------
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{
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"index" : {
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"analysis" : {
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"analyzer" : {
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"collation" : {
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"tokenizer" : "keyword",
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"filter" : ["icu_collation"]
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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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And here is a sample of custom collation:
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[source,js]
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--------------------------------------------------
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{
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"index" : {
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"analysis" : {
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"analyzer" : {
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"collation" : {
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"tokenizer" : "keyword",
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"filter" : ["myCollator"]
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}
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},
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"filter" : {
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"myCollator" : {
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"type" : "icu_collation",
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"language" : "en"
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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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[float]
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==== Options
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[horizontal]
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`strength`::
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The strength property determines the minimum level of difference considered significant during comparison.
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The default strength for the Collator is `tertiary`, unless specified otherwise by the locale used to create the Collator.
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Possible values: `primary`, `secondary`, `tertiary`, `quaternary` or `identical`.
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+
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See http://icu-project.org/apiref/icu4j/com/ibm/icu/text/Collator.html[ICU Collation] documentation for a more detailed
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explanation for the specific values.
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`decomposition`::
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Possible values: `no` or `canonical`. Defaults to `no`. Setting this decomposition property with
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`canonical` allows the Collator to handle un-normalized text properly, producing the same results as if the text were
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normalized. If `no` is set, it is the user's responsibility to insure that all text is already in the appropriate form
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before a comparison or before getting a CollationKey. Adjusting decomposition mode allows the user to select between
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faster and more complete collation behavior. Since a great many of the world's languages do not require text
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normalization, most locales set `no` as the default decomposition mode.
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[float]
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==== Expert options:
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[horizontal]
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`alternate`::
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Possible values: `shifted` or `non-ignorable`. Sets the alternate handling for strength `quaternary`
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to be either shifted or non-ignorable. What boils down to ignoring punctuation and whitespace.
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`caseLevel`::
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Possible values: `true` or `false`. Default is `false`. Whether case level sorting is required. When
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strength is set to `primary` this will ignore accent differences.
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`caseFirst`::
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Possible values: `lower` or `upper`. Useful to control which case is sorted first when case is not ignored
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for strength `tertiary`.
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`numeric`::
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Possible values: `true` or `false`. Whether digits are sorted according to numeric representation. For
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example the value `egg-9` is sorted before the value `egg-21`. Defaults to `false`.
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`variableTop`::
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Single character or contraction. Controls what is variable for `alternate`.
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`hiraganaQuaternaryMode`::
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Possible values: `true` or `false`. Defaults to `false`. Distinguishing between Katakana and
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Hiragana characters in `quaternary` strength .
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[float]
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=== ICU Tokenizer
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Breaks text into words according to UAX #29: Unicode Text Segmentation ((http://www.unicode.org/reports/tr29/)).
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[source,js]
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--------------------------------------------------
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{
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"index" : {
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"analysis" : {
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"analyzer" : {
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"collation" : {
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"tokenizer" : "icu_tokenizer",
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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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[float]
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=== ICU Normalization CharFilter
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Normalizes characters as explained http://userguide.icu-project.org/transforms/normalization[here].
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It registers itself by default under `icu_normalizer` or `icuNormalizer` using the default settings.
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Allows for the name parameter to be provided which can include the following values: `nfc`, `nfkc`, and `nfkc_cf`.
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Allows for the mode parameter to be provided which can include the following values: `compose` and `decompose`.
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Use `decompose` with `nfc` or `nfkc`, to get `nfd` or `nfkd`, respectively.
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Here is a sample settings:
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[source,js]
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--------------------------------------------------
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{
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"index" : {
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"analysis" : {
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"analyzer" : {
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"collation" : {
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"tokenizer" : "keyword",
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"char_filter" : ["icu_normalizer"]
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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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