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https://issues.apache.org/jira/browse/DERBY-2586?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12497371
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Anurag Shekhar commented on DERBY-2586:
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sorry for the late response.
In Blob/clob before making the changes the data was held in memory
depending on the free space in the page. So some times even huge
clob/blob can be used as String. In case of testPositionAggressive all
the tests were running in this mode and String.indexOf was giving result
very fast.
Once I changed the blob/clob to hold only 4k in memory and if it exceeds
use a file it started taking very long because of the file i/o over
heads. If we change the max buffer size (higher than 4k) we will be
getting better performance for clob/blob of length smaller than the new
value. But there may be risk of getting out of memory exception if we
keep the value large and there are too many active blob and clob.I think
we need not make the buffer size too large, as right now after making
the stream buffered we are able to get performance comparable to the
older implementation.
> BlobClob4BlobTest.tesPositionAgressive takes very long time
> -----------------------------------------------------------
>
> Key: DERBY-2586
> URL: https://issues.apache.org/jira/browse/DERBY-2586
> Project: Derby
> Issue Type: Bug
> Components: JDBC
> Reporter: Øystein Grøvlen
> Assigned To: Anurag Shekhar
> Fix For: 10.3.0.0
>
> Attachments: derby-2586.diff
>
>
> Dan reports that BlobClob4BlobTest.tesPositionAgressive takes very long to
> run:
> > In a test run (junit-all) of 5,816 fixtures that took 4124 seconds
> > (~68mins) *three* fixtures took 53% of the total time.
> >
> > testPositionAgressive 1564.684 seconds
> > testNetworkServerSecurityMechanism 497.280 seconds
> > testTypesInActionStatement 128.928 seconds
> Knut Anders reports that this behavior is fairly new:
> > It seems like it started taking a lot more time at revision 530085. I had
> > run the tests at an earlier revision.
> This was a check-in for DERBY-2346. Since Anurag is currently on vacation, I
> will try to look into this.
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