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https://issues.apache.org/jira/browse/SPARK-11661?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15075690#comment-15075690
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Russell Alexander Spitzer commented on SPARK-11661:
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This seems to have a slightly unintended consequence in the explain dialogue.
It basically makes it seem as if a source is always pushing down all of the
filters (even those it cannot handle)
This can have a confusing effect (I kept checking my code to see where I had
broken something :D )
{code: Title="Query plan for source where nothing is handled by C* Source"}
Filter ((((a#71 = 1) && (b#72 = 2)) && (c#73 = 1)) && (e#75 = 1))
+- Scan
org.apache.spark.sql.cassandra.CassandraSourceRelation@4b9cf75c[a#71,b#72,c#73,d#74,e#75,f#76,g#77,h#78]
PushedFilters: [EqualTo(a,1), EqualTo(b,2), EqualTo(c,1), EqualTo(e,1)]
{code}
Although the tell tale "Filter" step is present my first instinct would tell me
that the underlying source relation is using all of those filters.
{code: Title="Query plan for source where *everything* is handled by C* Source"}
Scan
org.apache.spark.sql.cassandra.CassandraSourceRelation@55d4456c[a#79,b#80,c#81,d#82,e#83,f#84,g#85,h#86]
PushedFilters: [EqualTo(a,1), EqualTo(b,2), EqualTo(c,1), EqualTo(e,1)]
{code}
I think this would be much clearer if we changed the metadata key to
"HandledFilters" and only listed those handled fully by the underlying source.
wdyt?
> We should still pushdown filters returned by a data source's unhandledFilters
> -----------------------------------------------------------------------------
>
> Key: SPARK-11661
> URL: https://issues.apache.org/jira/browse/SPARK-11661
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Reporter: Yin Huai
> Assignee: Yin Huai
> Priority: Blocker
> Fix For: 1.6.0
>
>
> We added unhandledFilters interface to SPARK-10978. So, a data source has a
> chance to let Spark SQL know that for those returned filters, it is possible
> that the data source will not apply them to every row. So, Spark SQL should
> use a Filter operator to evaluate those filters. However, if a filter is a
> part of returned unhandledFilters, we should still push it down. For example,
> our internal data sources do not override this method, if we do not push down
> those filters, we are actually turning off the filter pushdown feature.
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