[GitHub] [arrow-datafusion] jychen7 edited a comment on issue #1507: Python bindings create duplicated qualified fields after joining

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jychen7 edited a comment on issue #1507:
URL: https://github.com/apache/arrow-datafusion/issues/1507#issuecomment-1017052134


   Actually the problem is neither `datafusion` or `pydatafusion`, just different expection.
   
   `datafusion` allow duplicate columns in `ans`, but `pydatafusion` will raise error when `create_dataframe` when input columns are duplicated.
   e.g. `select x.c2, y.c2 from x join y using (c1) limit 1` shows
   ```
   +----+----+
   | c2 | c2 |
   +----+----+
   | 1  | 1  |
   +----+----+
   ```
   
   1. I test in MySQL 5.6 and PostgreSQL 9.6, they also show duplicate column names in output, e.g. http://sqlfiddle.com/#!9/a6c585/237251 and http://sqlfiddle.com/#!17/bf2fd/25993. This also align with "All bare column field names MUST not contain relation/table qualifier." in https://arrow.apache.org/datafusion/specification/output-field-name-semantic.html
   2. dataframe is correct too, since it is not expected to have duplicate input name. I believe the internal dataframe using in `ctx.sql` have different column name like `x.c2` and `y.c2`, but we trucate that when output


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