elasticsearch/elasticsearch — pull request #6796 by markharwood (2014-07-09 12:13:54+00:00)
Title: significant_terms agg new sampling option.

Avoids the use of FieldData in high-cardinality free-text fields by re-tokenizing samples of the top matching documents.
Also provides a de-duplication option to remove duplicated sections of text commonly found in free-text document fields in order to avoid skewing word usage stats and making bad keyword suggestions as a result.