How to read list of lists with class serialisation?

[AsWish]

Hi,

I generated following sample dataset with a column which is a list of list of ints, but I don't know how to read it with class serialisation:

I tried to define a class MyRecord with a column type List<List<int>> but got schema compile error:

System.AggregateException: One or more errors occurred. (failed to compile 'openingHours/list/element/list/element (System.Int32)') ---> System.FieldAccessException: failed to compile 'openingHours/list/element/list/element (System.Int32)' ---> System.InvalidOperationException: No coercion operator is defined between types 'System.Int32' and 'System.Collections.Generic.List`1[System.Int32]'.
    at System.Linq.Expressions.Expression.GetUserDefinedCoercionOrThrow(ExpressionType coercionType, Expression expression, Type convertToType)
   at System.Linq.Expressions.Expression.Convert(Expression expression, Type type, MethodInfo method)
   at System.Linq.Expressions.Expression.Convert(Expression expression, Type type)
   at Parquet.Serialization.Dremel.FieldAssemblerCompiler`1.InjectLevel(Expression rootVar, Type rootType, Field[] levelFields, List`1 path)
   at Parquet.Serialization.Dremel.FieldAssemblerCompiler`1.InjectColumn()
   at Parquet.Serialization.Dremel.FieldAssemblerCompiler`1.Compile()

Reproduce code:

   [TestClass]
   public class MyTest
   {
        class MyRecord
        {
            public List<List<int>> openingHours { get; set; }
        }
        
        [TestMethod]
        public async Task TestListOfListReadWrite()
        {
            var filePath = "C:\\tmp\\listoflist.parquet";

            // Write list of list using data column API, from UT "Two_level_rep_levels"
            var schema = new ParquetSchema(
                new ListField("openingHours",
                    new ListField("element",
                        new DataField<int>("element"))));

            var dc = new DataColumn(
                schema.GetDataFields()[0],
                new[] {
                    1, 2, 3, 4,
                    5, 6,

                    7, 8, 9,
                    10, 11, 12, 13 },
                new[] {
                    0, 2, 2, 2,
                    1, 2,

                    0, 2, 2,
                    1, 2, 2, 2 });
            await using(Stream fs = System.IO.File.OpenWrite(filePath)) {
                using(ParquetWriter writer = await ParquetWriter.CreateAsync(schema, fs)) {
                    using(ParquetRowGroupWriter groupWriter = writer.CreateRowGroup()) {
                        await groupWriter.WriteColumnAsync(dc);
                    }
                }
            }
            
            // read data with class serialization
            await using (var stream = new FileInfo(filePath).OpenRead()) {
                var records = ParquetSerializer.DeserializeAsync<MyRecord>(stream).Result;
                Console.Out.WriteLine(records.Count);
            }
        }
}

Any suggestions? Thanks!

[aloneguid]

I can't reproduce it without source file or have any idea what the source schema is. Feel free to come back if still relevant.