read and write simple maps with parquet.net

Author: Ivan Gavryliuk

src/Parquet.Test/MapsTest.cs

@@ -8,7 +8,7 @@ namespace Parquet.Test
 {
    public class MapsTest
    {
-      //[Fact]
+      [Fact]
       public void Simple_first_level_map_int_to_string()
       {
          var ds = new DataSet(
@@ -24,6 +24,8 @@ public void Simple_first_level_map_int_to_string()
          //ParquetWriter.WriteFile(ds, "c:\\tmp\\map.parquet");
 
          DataSet ds1 = DataSetGenerator.WriteRead(ds);
+
+         Assert.Equal("{1;[1=>one;2=>two]}", ds1[0].ToString());
       }
    }
 }

src/Parquet/Data/Schema/SchemaElement.cs

@@ -109,6 +109,19 @@ public SchemaElement(string name, Type elementType) : this()
          }
 
          UpdateFlags();
+
+         //hack: to be gone in vNext
+         if(IsMap)
+         {
+            SchemaElement sKey = _extra[0];
+            SchemaElement sValue = _extra[1];
+
+            sKey.MaxRepetitionLevel = MaxRepetitionLevel;
+            sValue.MaxRepetitionLevel = MaxRepetitionLevel;
+
+            sKey.MaxDefinitionLevel += (MaxDefinitionLevel + 1);
+            sValue.MaxDefinitionLevel += (MaxDefinitionLevel + 1);
+         }
       }
 
       internal SchemaElement(Thrift.SchemaElement tse, string nameOverride,