This task is for adding labels & descriptions into ElasticSearch and enabling prefix search to use them. Current progress plan:
[x] Implement the code for creating & indexing label fields
[x] Reindex testwiki and check that index looks sane
[x] Reindex wikidata and check that index looks sane (T162292)
[x] Add code that allows wbsearchentities to use search engine depending on query flag
[x] Setup test page comparing two searches and make an announcement on the list to gather user feedback.
[x] Collect feedback and bikeshed about search profiles, weights and result ranking, hopefully arriving to some workable weights profile. (T172467)
[x] Set up the config above in production and enable CirrusSearch on wbsearchentities by default (T175741)
[] Discuss & resolve question of how to display entity & title search together
[] Refactor code more to allow opensearch and other code using completionSearch() use the same code as wbsearchentities, in service of the results of the discussion above.
[] Implement the GUI part of the two items above.
[] Figure out how to properly index descriptions (T176903)
[] Make code to allow fulltext search to use entity search when appropriate (T178851).
[] Enable Cirrus searching for Special:Search
More detailed plan: https://www.wikidata.org/wiki/User:Smalyshev_(WMF)/Wikidata_search