`flattened` field documentation does not mention restrictions on keys or values - Githubissues

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`flattened` field documentation does not mention restrictions on keys or values #108226

Open axw opened 6 months ago

axw commented 6 months ago

The flattened field type has a couple of limits that are not documented at https://www.elastic.co/guide/en/elasticsearch/reference/current/flattened.html:

key+value+separator length cannot exceed the maximum Lucene term length: https://github.com/elastic/elasticsearch/blob/1bf95633181e71c97c26db26ac411299a547332d/server/src/main/java/org/elasticsearch/index/mapper/flattened/FlattenedFieldParser.java#L144-L158
Keys cannot have null bytes: https://github.com/elastic/elasticsearch/blob/1bf95633181e71c97c26db26ac411299a547332d/server/src/main/java/org/elasticsearch/index/mapper/flattened/FlattenedFieldParser.java#L135-L138

The latter issue is mentioned in https://github.com/elastic/elasticsearch/issues/90311 as a restriction that could potentially be removed. If nothing else, these limits should be documented to avoid surprises.

elasticsearchmachine commented 6 months ago

Pinging @elastic/es-docs (Team:Docs)

elasticsearchmachine commented 6 months ago

Pinging @elastic/es-search (Team:Search)

elasticsearchmachine commented 5 months ago

Pinging @elastic/es-storage-engine (Team:StorageEngine)