[jira] [Created] (PHOENIX-3073) Fast path for single-key point lookups

["Junegunn Choi (JIRA)" <ji...@apache.org>]

Junegunn Choi created PHOENIX-3073:
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             Summary: Fast path for single-key point lookups
                 Key: PHOENIX-3073
                 URL: https://issues.apache.org/jira/browse/PHOENIX-3073
             Project: Phoenix
          Issue Type: Improvement
            Reporter: Junegunn Choi
            Assignee: Junegunn Choi


While comparing Phoenix JDBC client to the native HBase Java client, I noticed that Phoenix client uses significantly more CPU time on the client machine. Profiling revealed that the majority of the time was spent on {{BaseResultIterators.getParallelScans()}}. This was surprising to me as I was only testing with simple point lookup queries.

Here's how I tested:

- {{SELECT /*+ SMALL SERIAL */ ID, DOCID FROM IMAGE WHERE ID = ?}}
    - {{IMAGE}} is a salted table with 100 salt buckets
    - {{ID}}, the primary key, was randomly selected in a small range so that the requests are served without disk I/O
- 20K/sec concurrent requests using 128 threads

{{getParallelScans()}} is quite expensive as it iterates over all regions of the table which can be many, only to return a single Scan object for this query. Since such a single-key point lookup is one of the most frequent type of requests in a typical OLTP application, I believe it makes sense to have a fast path for it. With the patch, the average CPU usage of the client during the workload dropped to 18.8% from 56.7% before the patch.



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