use cancast

apache · Feb 21, 2024 · ff91019 · ff91019
1 parent 2f7ac44
commit ff91019
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Showing 2 changed files with 7 additions and 5 deletions.
diff --git a/python/pyarrow/src/arrow/python/ipc.cc b/python/pyarrow/src/arrow/python/ipc.cc
@@ -77,12 +77,14 @@ Status CastingRecordBatchReader::Init(std::shared_ptr<RecordBatchReader> parent,
                            num_fields);
   }
 
-  // Try to cast an empty version of all the columns before succceeding
+  // Ensure all columns can be cast before succeeding
   compute::CastOptions options;
   for (int i = 0; i < num_fields; i++) {
-    ARROW_ASSIGN_OR_RAISE(auto empty_array, MakeEmptyArray(src->field(i)->type()));
-    options.to_type = schema->field(i)->type();
-    ARROW_ASSIGN_OR_RAISE(auto emtpy_array_dst, compute::Cast(empty_array, options));
+    if (!compute::CanCast(*src->field(i)->type(), *schema->field(i)->type())) {
+      return Status::NotImplemented("Field ", i, " cannot be cast from ",
+                                    src->field(i)->type()->ToString(), " to ",
+                                    schema->field(i)->type()->ToString());
+    }
   }
 
   parent_ = std::move(parent);

diff --git a/python/pyarrow/tests/test_cffi.py b/python/pyarrow/tests/test_cffi.py
@@ -578,7 +578,7 @@ def test_roundtrip_reader_capsule(constructor):
     obj = constructor(schema, batches)
 
     bad_schema = pa.schema({'ints': pa.int32()})
-    with pytest.raises(pa.lib.ArrowNotImplementedError, match="Unsupported cast"):
+    with pytest.raises(pa.lib.ArrowNotImplementedError, match="Field 0 cannot be cast"):
         obj.__arrow_c_stream__(bad_schema.__arrow_c_schema__())
 
     # Can work with matching schema