Colin Goodheart-Smithe 99aca9cdfc Enhances exists queries to reduce need for `_field_names` (#26930) ... * Enhances exists queries to reduce need for `_field_names` Before this change we wrote the name all the fields in a document to a `_field_names` field and then implemented exists queries as a term query on this field. The problem with this approach is that it bloats the index and also affects indexing performance. This change adds a new method `existsQuery()` to `MappedFieldType` which is implemented by each sub-class. For most field types if doc values are available a `DocValuesFieldExistsQuery` is used, falling back to using `_field_names` if doc values are disabled. Note that only fields where no doc values are available are written to `_field_names`. Closes #26770 * Addresses review comments * Addresses more review comments * implements existsQuery explicitly on every mapper * Reinstates ability to perform term query on `_field_names` * Added bwc depending on index created version * Review Comments * Skips tests that are not supported in 6.1.0 These values will need to be changed after backporting this PR to 6.x		2017-11-01 10:46:59 +00:00
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main	Enhances exists queries to reduce need for `_field_names` (#26930)	2017-11-01 10:46:59 +00:00
test	Don't refresh on `_flush` `_force_merge` and `_upgrade` (#27000)	2017-10-16 10:16:35 +02:00