Flink how to create table with the schema inferred from Avro input data

Question

I have loaded an Avro file in a Flink Dataset:

AvroInputFormat<GenericRecord> test = new AvroInputFormat<GenericRecord>(
        new Path("PathToAvroFile")
        , GenericRecord.class);
DataSet<GenericRecord> DS = env.createInput(test);

usersDS.print();

and here are the results of printing the DS:

{"N_NATIONKEY": 14, "N_NAME": "KENYA", "N_REGIONKEY": 0, "N_COMMENT": " pending excuses haggle furiously deposits. pending, express pinto beans wake fluffily past t"}
{"N_NATIONKEY": 15, "N_NAME": "MOROCCO", "N_REGIONKEY": 0, "N_COMMENT": "rns. blithely bold courts among the closely regular packages use furiously bold platelets?"}
{"N_NATIONKEY": 16, "N_NAME": "MOZAMBIQUE", "N_REGIONKEY": 0, "N_COMMENT": "s. ironic, unusual asymptotes wake blithely r"}
{"N_NATIONKEY": 17, "N_NAME": "PERU", "N_REGIONKEY": 1, "N_COMMENT": "platelets. blithely pending dependencies use fluffily across the even pinto beans. carefully silent accoun"}
{"N_NATIONKEY": 18, "N_NAME": "CHINA", "N_REGIONKEY": 2, "N_COMMENT": "c dependencies. furiously express notornis sleep slyly regular accounts. ideas sleep. depos"}
{"N_NATIONKEY": 19, "N_NAME": "ROMANIA", "N_REGIONKEY": 3, "N_COMMENT": "ular asymptotes are about the furious multipliers. express dependencies nag above the ironically ironic account"}
{"N_NATIONKEY": 20, "N_NAME": "SAUDI ARABIA", "N_REGIONKEY": 4, "N_COMMENT": "ts. silent requests haggle. closely express packages sleep across the blithely"}

Now I want to create a table from DS Dataset with the exactly the same schema of Avro file, I mean columns should be N_NATIONKEY, N_NAME, N_REGIONKEY, and N_COMMENT.

I know using the line:

tableEnv.registerDataSet("tbTest", DS, "field1, field2, ...");

I can create a table and set the columns, but I want the columns to be inferred automatically from data. Is it possible? In addition, I tried

tableEnv.registerDataSet("tbTest", DS);

but it creates a table with the schema:

root
 |-- f0: GenericType<org.apache.avro.generic.GenericRecord>

Answer 1

GenericRecord is a black-box for the Table & SQL API runtime as the number of fields and their datatype is undefined. I would recommend to use a Avro-generated class which extends SpecificRecord. Those specific types are also recognized by Flink's type system and you can properly address individual fields with proper data type.

Alternatively, you could implement a custom UDF that extracts fields with a proper datatype getAvroInt(f0, "myField"), getAvroString(f0, "myField") etc.

Some pseudo code for this:

class AvroStringFieldExtract extends ScalarFunction {
    public String eval(GenericRecord r, String fieldName) {
        return r.get(fieldName).toString();
    }
}

tableEnv.registerFunction("getAvroFieldString", new AvroStringFieldExtract())