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https://issues.apache.org/jira/browse/DERBY-2586?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12498209
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Øystein Grøvlen commented on DERBY-2586:
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> 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.
I think it is important that temporary storage is only used when the LOB is
updated. Hence, when reading a LOB, one should make sure that the LOB is not
written to temporary storage, regardless of size.
> 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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