[jira] [Created] (PHOENIX-1906) With large number of guideposts, queries that iterate over a small range gets starved when running concurrently with larger queries

["Mujtaba Chohan (JIRA)" <ji...@apache.org>]

Mujtaba Chohan created PHOENIX-1906:
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             Summary: With large number of guideposts, queries that iterate over a small range gets starved when running concurrently with larger queries
                 Key: PHOENIX-1906
                 URL: https://issues.apache.org/jira/browse/PHOENIX-1906
             Project: Phoenix
          Issue Type: Bug
            Reporter: Mujtaba Chohan


Consider the scenario with a single region server. Table has 500 guide posts (data is large enough that it won't fit either into HBase block or OS page cache so it gets blocked on disk I/O during scans) and running the following 2 queries concurrently with and without stats enabled:

{code}select count(*) from table{code}
{code}select * from table limit 10{code}

With stats *disabled*, average time for these two queries is 100sec and 100ms respectively. However with stats long running count aggregate query time drops to 8 second but limit query time increases to 3 seconds. Degradation in limit query time is even more evident when concurrency level is further increased.

[~jamestaylor]



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