Meta fields were locked down to not allow exotic options to the
underlying field types in #8143. This change fixes the docs
to no longer refer to the old settings.
closes#10879
The `exists` and `missing` filters need to merge postings lists of all existing
terms, which can be very costly, especially on high-cardinality fields. This
commit indexes the field names of a document under `_field_names` and reuses it
to speed up the `exists` and `missing` filters.
This is only enabled for indices that are created on or after Elasticsearch
1.3.0.
Close#5659
Jim Ferenczi
Clinton Gormley
Ryan Ernst
Simon Willnauer
Adrien Grand