Luca Cavanna 7dc3d3b78b
Add sort and collapse info to SearchHits transport serialization (#36555)
In order for CCS alternate execution mode (see #32125) to be able to do the final reduction step on the CCS coordinating node, we need to serialize additional info in the transport layer as part of the `SearchHits`, specifically:

- lucene `SortField[]` which contains info about the fields that sorting was performed on and their type, which depends on mappings (that the CCS node does not know about)
- collapse field (`String`) that field collapsing was executed on, if requested
- collapse values (`Object[]`) that field collapsing was based on, if requested

This info is needed to be able to reconstruct the `TopFieldDocs` or `CollapseFieldTopDocs` in the CCS coordinating node to feed the `mergeTopDocs` method and reduce multiple search responses received (one per cluster) into one.

This commit adds such information to the `SearchHits` class. It's nullable info that is not serialized through the REST layer. `SearchPhaseController` sets such info at the end of the hits reduction phase.
2018-12-14 12:22:54 +01:00
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