[jira] [Created] (ARROW-10514) [C++][Parquet] Data inconsistency in parquet-reader output modes

["Zosimova Zhanna (Jira)" <ji...@apache.org>]

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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