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From "Junegunn Choi (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (PHOENIX-3073) Fast path for single-key point lookups
Date Fri, 16 Jun 2017 05:42:00 GMT

     [ https://issues.apache.org/jira/browse/PHOENIX-3073?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Junegunn Choi updated PHOENIX-3073:
-----------------------------------
    Summary: Fast path for single-key point lookups  (was: Auto-detect when SMALL hint should
be applied)

> 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
>             Fix For: 4.12.0
>
>         Attachments: 3073-try.txt, 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.



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