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Posted to github@arrow.apache.org by "gaoxinge (via GitHub)" <gi...@apache.org> on 2023/02/04 02:07:33 UTC
[GitHub] [arrow-datafusion] gaoxinge opened a new issue, #5174: cast expression may cause duplicate column name error
gaoxinge opened a new issue, #5174:
URL: https://github.com/apache/arrow-datafusion/issues/5174
**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
This problem origin from https://github.com/dask-contrib/dask-sql/issues/948, which can be minimally reproduced by
```sql
SELECT 10, cast(10 as tinyint)
```
The sql above will cause the duplicate column name error. And this is because
- cast use the expr as column name
https://github.com/apache/arrow-datafusion/blob/224c682101949da57aebc36e92e5a881ef3040d4/datafusion/expr/src/expr.rs#L1203-L1210
- same column name is not valid
https://github.com/apache/arrow-datafusion/blob/224c682101949da57aebc36e92e5a881ef3040d4/datafusion/expr/src/logical_plan/builder.rs#L925-L948
**Describe the solution you'd like**
There are two soluntions here:
1. rename the column name of cast expression
For example, mysql use the whole cast expression as column name, like `CAST(Int64(10) AS Int8)` instead of `Int64(10)`. In this way, the column name of cast expression will be more precise, and also this can bypass the duplicate column name error.
2. remove the unique column name validation
In mysql and sql server, query support same column name. So I think we can remove the unique column name validation to make same column name coexist.
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[GitHub] [arrow-datafusion] comphead commented on issue #5174: cast expression may cause duplicate column name error
Posted by "comphead (via GitHub)" <gi...@apache.org>.
comphead commented on issue #5174:
URL: https://github.com/apache/arrow-datafusion/issues/5174#issuecomment-1416873162
Thanks @gaoxinge for reporting this, I'm planning to start work on this as @andygrove agreed here https://github.com/apache/arrow-datafusion/issues/3990#issuecomment-1370083263
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[GitHub] [arrow-datafusion] alamb commented on issue #5174: cast expression may cause duplicate column name error
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on issue #5174:
URL: https://github.com/apache/arrow-datafusion/issues/5174#issuecomment-1416845441
Also, possibly related -- https://github.com/apache/arrow-datafusion/issues/4723 from @comphead
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[GitHub] [arrow-datafusion] alamb commented on issue #5174: cast expression may cause duplicate column name error
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on issue #5174:
URL: https://github.com/apache/arrow-datafusion/issues/5174#issuecomment-1416845313
I think @andygrove and @xudong963 may have had thoughts on this topic previously
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[GitHub] [arrow-datafusion] gaoxinge commented on issue #5174: cast expression may cause duplicate column name error
Posted by "gaoxinge (via GitHub)" <gi...@apache.org>.
gaoxinge commented on issue #5174:
URL: https://github.com/apache/arrow-datafusion/issues/5174#issuecomment-1418362919
@alamb @comphead Thx for reply, and I see the progress and direction of this issue.
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[GitHub] [arrow-datafusion] gaoxinge closed issue #5174: cast expression may cause duplicate column name error
Posted by "gaoxinge (via GitHub)" <gi...@apache.org>.
gaoxinge closed issue #5174: cast expression may cause duplicate column name error
URL: https://github.com/apache/arrow-datafusion/issues/5174
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