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From "James Taylor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-1693) Stats sometimes cause query to execute more slowly
Date Tue, 03 Mar 2015 00:48:14 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-1693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14344175#comment-14344175
] 

James Taylor commented on PHOENIX-1693:
---------------------------------------

[~mujtabachohan] - is the slow case only when a major compaction has never occurred on the
table? Are statistics being populated prior to a major compaction occurring (as from the code
it seems like they wouldn't be, unless an UPDATE STATISTICS is manually run)?

We should first rule in/out whether its a data locality issue. If the actual data isn't co-located
with the region servers yet, but an UPDATE STATISTICS was done, that may explain the slowness,
as you'd be pull a bunch of data (per guidepost) over the wire between RS & HDFS server
to execute the query.



> Stats sometimes cause query to execute more slowly
> --------------------------------------------------
>
>                 Key: PHOENIX-1693
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-1693
>             Project: Phoenix
>          Issue Type: Bug
>            Reporter: Mujtaba Chohan
>
> After initial data load with Phoenix 4.3.0 with stats enabled for 500M FHA table using
Pherf, aggregate count queries over 5% or 15% of total rows are some times 2-5X slow compared
to queries without stats. Needs to investigate the root cause. 
> Observations:
> * After major compaction with new stats are re-generated and queries become fast compared
to tables without stats.
> * Trucating stats table after initial data load also makes queries perf. comparable to
previous Phoenix release with stats disabled.



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