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https://issues.apache.org/jira/browse/HBASE-9915?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13816350#comment-13816350
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Lars Hofhansl commented on HBASE-9915:
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[~jmspaggi] Yeah, did some count queries in Phoenix. Without patch they took
27s with the patch they take 14s. You'll see the improvement if (1) you use a
block encoder (like FAST_DIFF, etc) and (2) you added some columns to you scan
object (so that the ExplicitColumnTracker is used under the hood). I am not
sure any the the performance evaluation tests do that (and if not, we should
probably add that).
Making a trunk patch now for a full test run.
> Severe performance bug: isSeeked() in EncodedScannerV2 is always false
> ----------------------------------------------------------------------
>
> Key: HBASE-9915
> URL: https://issues.apache.org/jira/browse/HBASE-9915
> Project: HBase
> Issue Type: Bug
> Reporter: Lars Hofhansl
> Assignee: Lars Hofhansl
> Fix For: 0.98.0, 0.96.1, 0.94.14
>
> Attachments: 9915-0.94-v2.txt, 9915-0.94.txt, profile.png
>
>
> While debugging why reseek is so slow I found that it is quite broken for
> encoded scanners.
> The problem is this:
> AbstractScannerV2.reseekTo(...) calls isSeeked() to check whether scanner was
> seeked or not. If it was it checks whether the KV we want to seek to is in
> the current block, if not it always consults the index blocks again.
> isSeeked checks the blockBuffer member, which is not used by EncodedScannerV2
> and thus always returns false, which in turns causes an index lookup for each
> reseek.
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