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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9717) Allow filterRowKey to return a next key hint
Date Mon, 07 Oct 2013 06:41:43 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9717?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13787948#comment-13787948

Lars Hofhansl commented on HBASE-9717:

Hmm... filterKeyValue is called for each KV, though (unless you filter the row and return
a seek hint).
So if the row is included there is no penalty (provided you implement the filter correctly)
since filterKeyValue is called for each KV in any event; if the row is not to be include filterKeyValue
can decide so after seeing the first KV.

Also - currently - we read whole KVs (key/ts/etc and value) at the server, although that will
hopefully change in the future.

If there's a case that cannot be efficiently be implemented with filterKeyValue and seek hints,
I'd like to see that.

> Allow filterRowKey to return a next key hint
> --------------------------------------------
>                 Key: HBASE-9717
>                 URL: https://issues.apache.org/jira/browse/HBASE-9717
>             Project: HBase
>          Issue Type: New Feature
>          Components: Filters
>            Reporter: Mathias Herberts
> The Filter interface has a filterRowKey method which returns a boolean set to true if
the given row key should be filtered out.
> When a row key is filtered, it could be interesting to be able to provide the scanner
a hint about the next row key which should be examined. This could tremendously speed up scanning
in some cases.
> The logic could be similar to that of filterKeyValue with a helper method getNextRowKeyHint,
or even simpler, filterRowKey could return a byte[] which would be set to null to mean keep
the row, to the empty array to mean filter the row and there is not hint, and to a non empty
byte array to mean filter the row and here is a hint about the next key that should be scanned.

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