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[jira] [Created] (ARROW-3866) Column metadata is not transferred to tables in pyarrow


Seb Fru created ARROW-3866:
------------------------------

             Summary: Column metadata is not transferred to tables in pyarrow
                 Key: ARROW-3866
                 URL: https://issues.apache.org/jira/browse/ARROW-3866
             Project: Apache Arrow
          Issue Type: Bug
          Components: Python
            Reporter: Seb Fru


Hello everyone,

transferring this from Github for Pyarrow. While working with pyarrow I noticed that field metadata does not get carried foreward when creating a table out of several columns. Is this intended behaviour or is there a way to add column metadata later on? The last command in my example does not return anything.
 I also could not verify whether this data would be written to parquet later on, because I could not find a way to add field metadata directly to a table.

 
{code:java}
>>>import pyarrow as pa
>>>import pyarrow.parquet as pq 
>>>arr1 = pa.array([1,2]) 
>>>arr2 = pa.array([3,4]) 

>>>field1 = pa.field('field1', pa.int64()) 
>>>field2 = pa.field('field2', pa.int64()) 

>>>field1 = field1.add_metadata({'foo1': 'bar1'}) 
>>>field2 = field2.add_metadata({'foo2': 'bar2'}) 

>>>field1.metadata {b'foo1': b'bar1'} 
>>>field2.metadata {b'foo2': b'bar2'} 

>>>col1 = pa.column(field1, arr1) 
>>>col2 = pa.column(field2, arr2) 
>>>col1.field.metadata {b'foo1': b'bar1'} 

>>>tab = pa.Table.from_arrays([col1, col2]) 
>>>tab pyarrow.Table field1: int64 field2: int64 
>>>tab.column(0).field.metadata
{code}



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