[jira] [Commented] (PIG-4953) Predicate push-down will not run filters for single unary expressions

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

    [ https://issues.apache.org/jira/browse/PIG-4953?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15384396#comment-15384396 ] 

Ryan Blue commented on PIG-4953:
--------------------------------

A comment in the code states, "if the leaf is a unary operator it should be a FilterFunc in which case we don't try to extract partition filter conditions". This appears to be a stale comment because it refers to partition filter conditions (one of the subclasses), but this is being used for push-down filtering as well. Partition filtering will check {{isSupportedOpType}} that returns false for all unary expressions, so it is perfectly safe to call {{checkPushDown}} in the partition filtering case.

> Predicate push-down will not run filters for single unary expressions
> ---------------------------------------------------------------------
>
>                 Key: PIG-4953
>                 URL: https://issues.apache.org/jira/browse/PIG-4953
>             Project: Pig
>          Issue Type: Bug
>          Components: impl
>    Affects Versions: 0.15.0
>            Reporter: Ryan Blue
>            Assignee: Ryan Blue
>
> While testing PIG-4940, I noticed that a "is not null" predicate was not pushed down, but equality predicates were. The problem is that the {{FilterExtractor#visit}} method ignores anything that isn't a {{BinaryExpression}}. Pushing down {{UnaryExpression}} filters works if the expression is linked in by a binary expression, like "b is not null and c == 'val'".



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