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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9316) Use JoinedHeap between MUST_PASS_ALL filters to better leverage essential column family feature
Date Fri, 23 Aug 2013 03:32:52 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9316?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13748250#comment-13748250
] 

Lars Hofhansl commented on HBASE-9316:
--------------------------------------

No better ideas ATM, the dummy column is how I would have done it too, but that does not work
if you do not control the table.
Hmm... This is at odds with other requirements. For example take a look at: HBASE-8930 (which
Vasu is working on). That issue would ensure that a Filter is never evaluated for something
that is not projected.
                
> Use JoinedHeap between MUST_PASS_ALL filters to better leverage essential column family
feature 
> ------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-9316
>                 URL: https://issues.apache.org/jira/browse/HBASE-9316
>             Project: HBase
>          Issue Type: Bug
>            Reporter: James Taylor
>
> Currently, all column families in a MUST_PASS_ALL filter list are loaded in advance of
filtering. Instead, only the essential column family from the first filter should be loaded
and then its heap joined with subsequent essential column family from the next filter in the
list (probably up to some reasonable/configurable limit).
> One particular Phoenix use case for this is when a SQL query is trying to detect the
absence of a KeyValue (though a <column> IS NULL clause). Our workaround for a Phoenix
TABLE is to insert a known, empty key value with every row, or for a Phoenix VIEW (mapping
to an existing HBase table) to project everything. With this feature, we could instead use
a filter per column family and prevent the loading of the corresponding Store in many cases.

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