elasticsearch/elasticsearch — pull request #3830 by jpountz (2013-10-04 21:01:23+00:00)
Title: Improved warm-up of new segments.

* Merged segments are now warmed-up at the end of the merge operation instead
of _refresh, so that _refresh doesn't pay the price for the warm-up of merged
segments, which is often higher than flushed segments because of their size.
* Even when no _warmer is registered, some basic warm-up of the segments is
performed: norms, doc values (_version). This should help a bit people who
forget to register warmers.
* Eager loading support for field data: when one can't predict what terms will
be present in the index, it is tempting to use a match_all query in a warmer,
but in that case, query execution might not be much faster than field data
loading so having a warmer that only loads field data without running a query
can be useful.