[jira] [Created] (ARROW-10547) [Rust][DataFusion] Filter pushdown loses filters if below a user defined node

["Andrew Lamb (Jira)" <ji...@apache.org>]

Andrew Lamb created ARROW-10547:
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             Summary: [Rust][DataFusion] Filter pushdown loses filters if below a user defined node
                 Key: ARROW-10547
                 URL: https://issues.apache.org/jira/browse/ARROW-10547
             Project: Apache Arrow
          Issue Type: Bug
            Reporter: Andrew Lamb
            Assignee: Andrew Lamb


I have a LogicalPlan like this (where "Extension" is some extension node type):

{code}
    Extension [non_null_column:Utf8]
      Filter: #state Eq Utf8("MA") [city:Utf8;N, state:Utf8;N, borough:Utf8;N]
        InMemoryScan: projection=None [city:Utf8;N, state:Utf8;N, borough:Utf8;N]
{code}

When I run this plan through {{ExecutionContext::optimize}} the plan that results is as follows (note the filter has been lost):

{code}
    Extension [non_null_column:Utf8]
      InMemoryScan: projection=Some([0, 1, 2]) [city:Utf8;N, state:Utf8;N, borough:Utf8;N]
{code}

I have debugged the problem and the root cause of the issue is that the FilterPushdown logic is not recursing into the inputs of user defined nodes. I will get a PR up showing and fixing the problem.

More generally, I am not sure how / if the filter pushdown logic would work if there are multiple child inputs as no existing LogicalPlan variant his multiple inputs at this time. We will have to handle this when / if we want to support joins (typically filters get  pushed down each join input if possible)




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