CBAS some bigfun query takes 185sec to run during 45M users scale level (.7B total rows) bigfun test

When running bigfun_query_10m test some of the queries took 100sec to finish.

This test does the following.

• Populates bigfun dataset (at 10M gbook user scale level, ie. 160M rows) in Couchbase.
• Connect Couchbase bucket with data sets in Analtyics, wait for them to be populated in Analytics.
• Start 3 threads, each thread run all bigfun queries (3 times each) and report the server side execution latency.
• Meanwhile there is a background process keep inserting new document into Couchbase and query Analytics to make sure it is appearing in Analytics side in 10 minutes.

From the following test on build 991:

http://perf.jenkins.couchbase.com/job/oceanus-cbas/283/

Q13 Select left-outer equi-join (User message nested join user_since range 14 years send_time range 14 years) and Q13 Select left-outer equi-join indexnl (User message nested join user_since range 14 years send_time range 14 years skip user_since index) are taking about 100 seconds to run. But the involved tables are about 30G in sizes. With 2 nodes of a SSD disk capable of 500M/sec read bytes, if bottleneck is just IO, it should be done in 30 seconds.