[jira] [Created] (SPARK-32639) Support GroupType parquet mapkey field

["Chen Zhang (Jira)" <ji...@apache.org>]

Chen Zhang created SPARK-32639:
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             Summary: Support GroupType parquet mapkey field
                 Key: SPARK-32639
                 URL: https://issues.apache.org/jira/browse/SPARK-32639
             Project: Spark
          Issue Type: Bug
          Components: SQL
    Affects Versions: 3.0.0, 2.4.6
            Reporter: Chen Zhang


I have a parquet file, and the MessageType recorded in the file is:
{code:java}
message parquet_schema {
  optional group value (MAP) {
    repeated group key_value {
      required group key {
        optional binary first (UTF8);
        optional binary middle (UTF8);
        optional binary last (UTF8);
      }
      optional binary value (UTF8);
    }
  }
}{code}
 

Use +spark.read.parquet("000.snappy.parquet")+ to read the file. Spark will throw an exception when converting Parquet MessageType to Spark SQL StructType:
{code:java}
AssertionError(Map key type is expected to be a primitive type, but found...)
{code}
 

Use +spark.read.schema("value MAP<STRUCT<first:STRING, middle:STRING, last:STRING>, STRING>").parquet("000.snappy.parquet")+ to read the file, spark returns the correct result .

According to the parquet project document (https://github.com/apache/parquet-format/blob/master/LogicalTypes.md#maps), the mapKey in the parquet format does not need to be a primitive type.

 
Note: This parquet file is not written by spark, because spark will write additional sparkSchema string information in the parquet file. When Spark reads, it will directly use the additional sparkSchema information in the file instead of converting Parquet MessageType to Spark SQL StructType.


I will submit a PR later.



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