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https://issues.apache.org/jira/browse/ARROW-11678?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17291643#comment-17291643
]
ARF commented on ARROW-11678:
-----------------------------
I modified the issue to take into account [~westonpace]'s explanations and
focussed it on the "warning to user" aspect.
> [python] Warn users if ParquetWriter coerces an explicitly defined schema
> -------------------------------------------------------------------------
>
> Key: ARROW-11678
> URL: https://issues.apache.org/jira/browse/ARROW-11678
> Project: Apache Arrow
> Issue Type: Improvement
> Components: Python
> Affects Versions: 3.0.0
> Reporter: ARF
> Priority: Minor
>
> pyarrow should warn users if it coerces a explicitly defined schema. Not
> warning the user leads to confusing behavious as illustrated below:
>
> {color:#af00db}import{color}{color:#000000}
> {color}{color:#267f99}pyarrow{color}{color:#000000}
> {color}{color:#af00db}as{color}{color:#000000} {color}{color:#267f99}pa{color}
> {color:#af00db}import{color}{color:#000000}
> {color}{color:#267f99}pyarrow{color}{color:#000000}.{color}{color:#267f99}parquet{color}{color:#000000}
> {color}{color:#af00db}as{color}{color:#000000}
> {color}{color:#267f99}pq{color}
> {color:#001080}schema{color}{color:#000000} =
> {color}{color:#267f99}pa{color}{color:#000000}.schema({{color}
> {color:#000000} {color}{color:#a31515}'code'{color}{color:#000000}:
> {color}{color:#267f99}pa{color}{color:#000000}.uint32(),{color}
> })
> with{color:#000000}
> {color}{color:#267f99}pq{color}{color:#000000}.{color}{color:#267f99}ParquetWriter{color}{color:#000000}({color}{color:#a31515}'test_metadata.parquet'{color}{color:#000000},
> {color}{color:#001080}schema{color}{color:#000000})
> {color}{color:#af00db}as{color}{color:#000000}
> {color}{color:#001080}pqwriter{color}{color:#000000}:{color}
> {color:#000000} {color}{color:#001080}code{color}{color:#000000} =
> {color}{color:#098658}111000{color}
> {color:#000000} {color}{color:#001080}table{color}{color:#000000} =
> {color}{color:#267f99}pa{color}{color:#000000}.Table.from_pydict({{color}
> {color:#000000} {color}{color:#a31515}'code'{color}{color:#000000}:
> {color}{color:#267f99}pa{color}{color:#000000}.nulls({color}{color:#098658}10{color}{color:#000000},
>
> {color}{color:#001080}schema{color}{color:#000000}.field({color}{color:#a31515}'code'{color}{color:#000000}).type).fill_null({color}{color:#001080}code{color}{color:#000000}),{color}
> {color:#000000} }){color}
> {color:#000000}
> {color}{color:#001080}pqwriter{color}{color:#000000}.{color}{color:#795e26}write_table{color}{color:#000000}({color}{color:#001080}table{color}{color:#000000}){color}
> {color:#001080}existing_table{color}{color:#000000} =
> {color}{color:#267f99}pq{color}{color:#000000}.{color}{color:#795e26}read_table{color}{color:#000000}({color}{color:#a31515}'test_metadata.parquet'{color}{color:#000000}){color}
> {color:#af00db}with{color}{color:#000000}
> {color}{color:#267f99}pq{color}{color:#000000}.{color}{color:#267f99}ParquetWriter{color}{color:#000000}({color}{color:#a31515}'test_metadata.parquet'{color}{color:#000000},
> {color}{color:#001080}schema{color}{color:#000000})
> {color}{color:#af00db}as{color}{color:#000000}
> {color}{color:#001080}pqwriter{color}{color:#000000}:{color}
> {color:#000000}
> {color}{color:#001080}pqwriter{color}{color:#000000}.{color}{color:#795e26}write_table{color}{color:#000000}({color}{color:#001080}existing_table{color}{color:#000000}){color}
>
>
> ----
> *Error Message:*
> ValueError: Table schema does not match schema used to create file:
> table:
> code: int64
> – field metadata –
> PARQUET:field_id: '1' vs.
> file:
> code: uint32
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