[jira] Commented: (HBASE-2198) SingleColumnValueFilter should be able to find the column value even when it's not specifically added as input on the scan.

["stack (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-2198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12831599#action_12831599 ] 

stack commented on HBASE-2198:
------------------------------

Its by design.  High-level in the Scan object you say what you are interested in and then the filter works against the Scan specification.

I like your suggestion A above.  Can you make a patch for that?

I think you need a new filter, one that allows filtering against one set of columns but only returns columns out of a different set of columns if a row passes a filter.

> SingleColumnValueFilter should be able to find the column value even when it's not specifically added as input on the scan.
> ---------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-2198
>                 URL: https://issues.apache.org/jira/browse/HBASE-2198
>             Project: Hadoop HBase
>          Issue Type: Improvement
>          Components: filters
>    Affects Versions: 0.20.3
>            Reporter: Ferdy
>
> Whenever applying a SingleColumnValueFilter to a Scan that has specific columns as it's input (but not the column to be checked in the Filter), the Filter won't be able to find the value that it should be checking.
> For example, let's say we want to do a scan, but we only need COLUMN_2 columns. Furthermore, we only want rows that have a specific value for COLUMN_1. Using the following code won't do the trick:
> Scan scan = new Scan();
> scan.addColumn(FAMILY, COLUMN_2);
> SingleColumnValueFilter filter = new SingleColumnValueFilter(FAMILY, COLUMN_1, CompareOp.EQUAL, TEST_VALUE);
> filter.setFilterIfMissing(true);
> scan.setFilter(filter);
> However, we can make it work when specifically also adding the tested column as an input column:
> scan.addColumn(FAMILY, COLUMN_1);
> Is this by design? Personally I think that adding a filter with columns tests should not bother the user to check that it's also on the input. It is prone to bugs.
> I suggest either one of 3 solutions:
> A) Update the Javadoc of Filter / SingleColumnValueFilter / possibly other affecting Filters to indicate this behaviour.
> B) Fix the problem client-side (i.e. prior to using a Scan object, it should check that the corresponding inputs for filters are set, but only if the user has configured specific input columns in the first place). This is perhaps inefficient performance-wise, because unnecessary inputs columns are returned to the user. (Inputs that would only have to be used for filtering).
> C) Fix the problem server-side. This would me most efficient, because the input column would only be read to do filtering at the regionserver.
> What do you think?

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