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Junegunn Choi commented on PHOENIX-3073: ---------------------------------------- I also found that the client overhead for this particular query was greatly increased recently due to the following change (PHOENIX-3040): https://github.com/apache/phoenix/commit/f9420e6fb8d635572a7049527db0cc513dbeebe6#diff-8c3d3f644c66ef36d5bc604f017fabfcL144 With the change, the query started to use guideposts (isPointLookup = true, plan.isSerial() = false) and it turns out to be quite costly on the client side. The client CPU usage for the same workload before PHOENIX-3040 is 22.3%. > 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 > Attachments: PHOENIX-3073.patch > > > 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. -- This message was sent by Atlassian JIRA (v6.3.4#6332)