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50 lines
1.8 KiB
Markdown
50 lines
1.8 KiB
Markdown
---
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mapped_pages:
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- https://www.elastic.co/guide/en/elasticsearch/reference/current/analysis-normalizers.html
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---
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# Normalizers [analysis-normalizers]
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Normalizers are similar to analyzers except that they may only emit a single token. As a consequence, they do not have a tokenizer and only accept a subset of the available char filters and token filters. Only the filters that work on a per-character basis are allowed. For instance a lowercasing filter would be allowed, but not a stemming filter, which needs to look at the keyword as a whole. The current list of filters that can be used in a normalizer definition are: `arabic_normalization`, `asciifolding`, `bengali_normalization`, `cjk_width`, `decimal_digit`, `elision`, `german_normalization`, `hindi_normalization`, `indic_normalization`, `lowercase`, `pattern_replace`, `persian_normalization`, `scandinavian_folding`, `serbian_normalization`, `sorani_normalization`, `trim`, `uppercase`.
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Elasticsearch ships with a `lowercase` built-in normalizer. For other forms of normalization, a custom configuration is required.
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## Custom normalizers [_custom_normalizers]
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Custom normalizers take a list of [character filters](/reference/text-analysis/character-filter-reference.md) and a list of [token filters](/reference/text-analysis/token-filter-reference.md).
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```console
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PUT index
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{
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"settings": {
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"analysis": {
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"char_filter": {
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"quote": {
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"type": "mapping",
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"mappings": [
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"« => \"",
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"» => \""
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]
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}
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},
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"normalizer": {
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"my_normalizer": {
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"type": "custom",
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"char_filter": ["quote"],
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"filter": ["lowercase", "asciifolding"]
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}
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}
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}
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},
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"mappings": {
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"properties": {
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"foo": {
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"type": "keyword",
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"normalizer": "my_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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