I don't think we're actually planning on using them so this is probably very low priority for us, but I found that searching for only the "Initiative" document type (which appears like these: https://secure.phabricator.com/I1 https://secure.phabricator.com/I2) returns this error:
HTTPFutureHTTPResponseStatus
[HTTP/400]
{"error":"SearchPhaseExecutionException[Failed to execute phase [query], all shards failed; shardFailures {[i5bA3UBCTgC2Bmr1Px8aYQ][phabricatormain][0]: RemoteTransportException[[elastic1031][inet[/10.64.48.55:9300]][search/phase/query]]; nested: SearchParseException[[phabricatormain][0]: from[-1],size[-1]: Parse Failure [Failed to parse source [{\"sort\":[{\"dateCreated\":\"desc\"}],\"from\":0,\"size\":101}]]]; nested: SearchParseException[[phabricatormain][0]: from[-1],size[-1]: Parse Failure [No mapping ...