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Normalizers
editNormalizers
editThis functionality is in beta and is subject to change. The design and code is less mature than official GA features and is being provided as-is with no warranties. Beta features are not subject to the support SLA of official GA features.
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.
Custom normalizers
editElasticsearch does not ship with built-in normalizers so far, so the only way to get one is by building a custom one. Custom normalizers take a list of char character filters and a list of token filters.
PUT index { "settings": { "analysis": { "char_filter": { "quote": { "type": "mapping", "mappings": [ "« => \"", "» => \"" ] } }, "normalizer": { "my_normalizer": { "type": "custom", "char_filter": ["quote"], "filter": ["lowercase", "asciifolding"] } } } }, "mappings": { "type": { "properties": { "foo": { "type": "keyword", "normalizer": "my_normalizer" } } } } }