Index - Aggregation latency increase between Neo builds 2174 and 2175

[This MB covers the apparent Index Service regression between 7.1.0 builds 2174 and 2175. Separate MB-50764 has been cloned from it that covers the apparent Query Service regression between 7.1.0 builds 2172 and 2173.

Index and Query changes delivered to build 2175:

http://changelog.build.couchbase.com/?product=couchbase-server&fromVersion=7.1.0&fromBuild=2174&toVersion=7.1.0&toBuild=2175&f_backup=off&f_cbbs=off&f_indexing=on&f_kv_engine=off&f_magma=off&f_ns_server=off&f_plasma=off&f_product-metadata=off&f_query=on&f_query-ee=on&f_testrunner=off&f_udf-api=off

--Kevin Cherkauer]

Aggregation and window query latency has increased slightly. Build 2172 is the last good build then it seems like there might be two different increases between 2172 and 2175.

90th percentile query latency (ms), AG1, Aggregation query, Plasma, not_bounded, s=1 c=1 i=1

http://showfast.sc.couchbase.com/#/timeline/Linux/n1ql/aggregation/Latency

2172 - http://perf.jenkins.couchbase.com/job/arke/9955/ - 580

2173 - http://perf.jenkins.couchbase.com/job/arke/9956/ - 615

2174 - http://perf.jenkins.couchbase.com/job/arke/9957/ - 610

2175 - http://perf.jenkins.couchbase.com/job/arke/9958/ - 684

Comparison -

2172 -2175: http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=arke_710-2172_access_886e&snapshot=arke_710-2175_access_60cf

http://changelog.build.couchbase.com/?product=couchbase-server&fromVersion=7.1.0&fromBuild=2172&toVersion=7.1.0&toBuild=2175&f_kv_engine=off&f_magma=off&f_ns_server=off&f_product-metadata=off&f_query=on&f_udf-api=off&f_backup=off&f_cbbs=off&f_indexing=off&f_plasma=off&f_query-ee=on&f_testrunner=off