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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