[GitHub] [arrow-datafusion] houqp commented on issue #670: unexpected schema field name conflicts in joins

[GitBox <gi...@apache.org>]

houqp commented on issue #670:
URL: https://github.com/apache/arrow-datafusion/issues/670#issuecomment-873638959


   I think this might have something to do with our projection push down logic:
   
   ```
   > SELECT
     t1.c9 x, t1.c1 c1
   FROM test t1
   INNER JOIN test t2
   ON t1.c9 = t2.c9
   ORDER BY x;
   [datafusion/src/execution/dataframe_impl.rs:148] &plan = Sort: #x ASC NULLS FIRST
     Projection: #t1.c9 AS x, #t1.c1 AS c1
       Join: #t1.c9 = #t2.c9
         TableScan: t1 projection=Some([0, 1])
         TableScan: t2 projection=Some([0, 1])
   ```
   
   Noticed `c1` got pushed down to `t2` table scan as well even though it's not being projected. Most likely the projection push down logic is not distinguishing between column names and aliases.


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