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https://issues.apache.org/jira/browse/PHOENIX-29?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13920289#comment-13920289
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Hudson commented on PHOENIX-29:
-------------------------------
SUCCESS: Integrated in Apache Phoenix - Branch:master #105 (See
[https://builds.apache.org/job/Phoenix/105/])
PHOENIX-76 Fix perf regression due to PHOENIX-29 (JamesTaylor) (jamestaylor:
rev 2581c20fba120466e4d1337e6ba086a435a07f2a)
* phoenix-core/src/main/java/org/apache/phoenix/iterate/ParallelIterators.java
> Add custom filter to more efficiently navigate KeyValues in row
> ---------------------------------------------------------------
>
> Key: PHOENIX-29
> URL: https://issues.apache.org/jira/browse/PHOENIX-29
> Project: Phoenix
> Issue Type: Bug
> Reporter: James Taylor
> Assignee: Anoop Sam John
> Fix For: 3.0.0
>
> Attachments: PHOENIX-29.patch, PHOENIX-29_V2.patch,
> PHOENIX-29_V5.patch, PHOENIX-29_v3.patch, PHOENIX-29_v4.patch
>
>
> Currently HBase is 50% faster at selecting the first KV in a row than in
> selecting any other column. The reason is that when you project a column into
> a Scan, HBase uses its ExplicitColumTracker which does a reseek to the
> column. The only case where this is not necessary is when the column is the
> first one.
> In most cases (unless you have thousands of versions), it'd be more efficient
> to just do a NEXT instead of a reseek (especially if your KV is the next
> one). We can provide our own custom filter through which we pass two lists:
> 1) all KVs referenced in the select expressions. These are the only ones that
> need to be returned back to the client which is another advantage we'd get
> writing this custom filter.
> 2) all KVs referenced in the WHERE clause.
> The filter could sort the KVs using the standard KeyValue.COMPARATOR and
> merge between them and the incoming KVs, using NEXT instead of a reseek. We
> could potentially use a reseek if the number of columns in the table is
> beyond a certain threshold.
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