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