[Fix] Replace children() with fields(), because children() no longer works in Arrow library greater than v6.0.0 (#8)

Co-authored-by: LeAnhMinh <tsdv@localhost.localdomain>

Author: MinhLA1410

.gitignore

@@ -4,4 +4,4 @@
 *.bc
 regression.diffs
 regression.out
-results
+results

src/common.cpp

@@ -131,7 +131,7 @@ bytes_to_postgres_type(const char *bytes, arrow::DataType *arrow_type)
 arrow::Type::type
 get_arrow_list_elem_type(arrow::DataType *type)
 {
-    auto children = type->children();
+    auto children = type->fields();
 
     Assert(children.size() == 1);
     return children[0]->type()->id();

src/parquet_impl.cpp

@@ -659,7 +659,7 @@ extract_parquet_fields(const char *path, const char *dirname, Aws::S3::S3Client
                     Oid     pg_subtype;
                     bool    error = false;
 
-                    if (type->children().size() != 1)
+                    if (type->fields().size() != 1)
                         throw std::runtime_error("lists of structs are not supported");
 
                     subtype_id = get_arrow_list_elem_type(type.get());