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https://issues.apache.org/jira/browse/ARROW-7245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17578136#comment-17578136
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Clark Zinzow commented on ARROW-7245:
-------------------------------------
+1 to having `Concatenate` going through the type promotion logic in the
compute layer; I'm currently running into a similar issue with concatenating
tables with different numeric types that can certainly be promoted to a common
numeric type. I'm currently working around this in application code by doing
manual type promotion of each column to the common dtype across that column in
all tables (mimicking Arrow's internal type promotion logic
[here|https://github.com/apache/arrow/blob/6cc37cf2d1ba72c46b64fbc7ac499bd0d7296d20/cpp/src/arrow/compute/kernels/codegen_internal.cc#L145-L338]))
before concatenating the tables.
Here is a pyarrow MRP:
```python
In [1]: t1 = pa.table({"a": pa.array([1, 2], type=pa.int16())})
In [2]: t2 = pa.table({"a": pa.array([3, 4], type=pa.int64())})
In [3]: pa.concat_tables([t1, t2])
---------------------------------------------------------------------------
ArrowInvalid Traceback (most recent call last)
<ipython-input-91-40afec1155a5> in <module>
----> 1 pa.concat_tables([t1, t2])
~/.local/lib/python3.7/site-packages/pyarrow/table.pxi in
pyarrow.lib.concat_tables()
~/.local/lib/python3.7/site-packages/pyarrow/error.pxi in
pyarrow.lib.pyarrow_internal_check_status()
~/.local/lib/python3.7/site-packages/pyarrow/error.pxi in
pyarrow.lib.check_status()
ArrowInvalid: Schema at index 1 was different:
a: int16
vs
a: int64
```
> [C++] Allow automatic String -> LargeString promotions when concatenating
> tables
> --------------------------------------------------------------------------------
>
> Key: ARROW-7245
> URL: https://issues.apache.org/jira/browse/ARROW-7245
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Reporter: Wes McKinney
> Priority: Major
>
> inspired by GitHub issue https://github.com/apache/arrow/issues/5874
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