Zosimova Zhanna created ARROW-10514:
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Summary: [C++][Parquet] Data inconsistency in parquet-reader
output modes
Key: ARROW-10514
URL: https://issues.apache.org/jira/browse/ARROW-10514
Project: Apache Arrow
Issue Type: Bug
Components: C++
Reporter: Zosimova Zhanna
Attachments:
0001-Make-the-column-name-the-same-for-both-output-format.patch
I tried reading description for Parquet
[file|[https://github.com/ClickHouse/ClickHouse/blob/master/tests/queries/0_stateless/data_parquet/nested_maps.snappy.parquet]]
with nested maps using [parquet-reader
tool|[https://github.com/apache/arrow/blob/master/cpp/tools/parquet/parquet_reader.cc]].
This file has the following structure:
{code:java}
required group field_id=0 spark_schema {
optional group field_id=1 a (Map) {
repeated group field_id=2 key_value {
required binary field_id=3 key (String);
optional group field_id=4 value (Map) {
repeated group field_id=5 key_value {
required int32 field_id=6 key;
required boolean field_id=7 value;
}
}
}
}
required int32 field_id=8 b;
required double field_id=9 c;
} {code}
When I print it using DebugPrint, I see:
{code:java}
$ ./parquet-reader nested_maps.snappy.parquet --only-metadata
<some text is omitted for the sake of readability>
Column 0: a.key_value.key (BYTE_ARRAY/UTF8)
Column 1: a.key_value.value.key_value.key (INT32)
Column 2: a.key_value.value.key_value.value (BOOLEAN)
Column 3: b (INT32)
Column 4: c (DOUBLE)
</some text is omitted for the sake of readability>{code}
When I pring it using JSONPrint, I see:
{code:java}
$ ./parquet-reader nested_maps.snappy.parquet --json
<some text is omitted for the sake of readability>
"Columns": [
{ "Id": "0", "Name": "key", "PhysicalType": "BYTE_ARRAY", "ConvertedType":
"UTF8", "LogicalType": {"Type": "String"} },
{ "Id": "1", "Name": "key", "PhysicalType": "INT32", "ConvertedType": "NONE",
"LogicalType": {"Type": "None"} },
{ "Id": "2", "Name": "value", "PhysicalType": "BOOLEAN", "ConvertedType":
"NONE", "LogicalType": {"Type": "None"} },
{ "Id": "3", "Name": "b", "PhysicalType": "INT32", "ConvertedType": "NONE",
"LogicalType": {"Type": "None"} },
{ "Id": "4", "Name": "c", "PhysicalType": "DOUBLE", "ConvertedType": "NONE",
"LogicalType": {"Type": "None"} }
]
</some text is omitted for the sake of readability>{code}
Column 0 and Column 1 has the same Name in JSON output. That's very confusing.
It would be more correct to output the full path of the column (key ->
a.key_value.key).
This can be corrected by changing a single line:
[https://github.com/apache/arrow/blob/master/cpp/src/parquet/printer.cc#L218]
The proposed patch in the attachment
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