private static TypeInfo generateMapTypeInfo(Schema schema,
      Set<Schema> seenSchemas) throws AvroSerdeException {
    assert schema.getType().equals(Schema.Type.MAP);
    Schema valueType = schema.getValueType();
    TypeInfo ti = generateTypeInfo(valueType, seenSchemas);

    return TypeInfoFactory.getMapTypeInfo(TypeInfoFactory.getPrimitiveTypeInfo("string"), ti);
  }
Generate a TypeInfo for an Avro Map.  This is made slightly simpler in that
Avro only allows maps with strings for keys.
serde/src/java/org/apache/hadoop/hive/serde2/avro/SchemaToTypeInfo.java