[GitHub] [arrow] nirandaperera commented on a change in pull request #10721: ARROW-11673 - [C++] Casting dictionary type to use different index type

[GitBox <gi...@apache.org>]

nirandaperera commented on a change in pull request #10721:
URL: https://github.com/apache/arrow/pull/10721#discussion_r670450370



##########
File path: cpp/src/arrow/compute/kernels/scalar_cast_dictionary.cc
##########
@@ -0,0 +1,123 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+// Implementation of casting to dictionary type
+
+#include <arrow/util/bitmap_ops.h>
+
+#include "arrow/array/builder_primitive.h"
+#include "arrow/compute/cast_internal.h"
+#include "arrow/compute/kernels/scalar_cast_internal.h"
+#include "arrow/compute/kernels/util_internal.h"
+#include "arrow/util/int_util.h"
+
+namespace arrow {
+using internal::CopyBitmap;
+
+namespace compute {
+namespace internal {
+
+Status CastDictionary(KernelContext* ctx, const ExecBatch& batch, Datum* out) {
+  const CastOptions& options = CastState::Get(ctx);
+  auto out_type = std::static_pointer_cast<DictionaryType>(out->type());
+
+  // if out type is same as in type, return input
+  if (out_type->Equals(batch[0].type())) {
+    *out = batch[0];
+    return Status::OK();
+  }
+
+  if (batch[0].is_scalar()) {  // if input is scalar
+    auto in_scalar = std::static_pointer_cast<DictionaryScalar>(batch[0].scalar());
+
+    // if invalid scalar, return null scalar
+    if (!in_scalar->is_valid) {
+      *out = MakeNullScalar(out_type);
+      return Status::OK();
+    }
+
+    Datum casted_index, casted_dict;
+    if (in_scalar->value.index->type->Equals(out_type->index_type())) {
+      casted_index = in_scalar->value.index;
+    } else {
+      ARROW_ASSIGN_OR_RAISE(casted_index,
+                            Cast(in_scalar->value.index, out_type->index_type(), options,
+                                 ctx->exec_context()));
+    }
+
+    if (in_scalar->value.dictionary->type()->Equals(out_type->value_type())) {
+      casted_dict = in_scalar->value.dictionary;
+    } else {
+      ARROW_ASSIGN_OR_RAISE(
+          casted_dict, Cast(in_scalar->value.dictionary, out_type->value_type(), options,
+                            ctx->exec_context()));
+    }
+
+    *out = std::static_pointer_cast<Scalar>(
+        DictionaryScalar::Make(casted_index.scalar(), casted_dict.make_array()));
+
+    return Status::OK();
+  }
+
+  // if input is array
+  const std::shared_ptr<ArrayData>& in_array = batch[0].array();
+  auto in_type = std::static_pointer_cast<DictionaryType>(in_array->type);
+
+  ArrayData* out_array = out->mutable_array();
+
+  if (in_type->index_type()->Equals(out_type->index_type())) {
+    out_array->buffers[0] = in_array->buffers[0];
+    out_array->buffers[1] = in_array->buffers[1];
+  } else {
+    // for indices, create a dummy ArrayData with index_type()
+    const std::shared_ptr<ArrayData>& indices_arr =
+        ArrayData::Make(in_type->index_type(), in_array->length, in_array->buffers,
+                        in_array->GetNullCount(), in_array->offset);
+    ARROW_ASSIGN_OR_RAISE(auto casted_indices, Cast(indices_arr, out_type->index_type(),
+                                                    options, ctx->exec_context()));
+    out_array->buffers[0] = std::move(casted_indices.array()->buffers[0]);
+    out_array->buffers[1] = std::move(casted_indices.array()->buffers[1]);
+  }
+
+  // data (dict)
+  if (in_type->index_type()->Equals(out_type->index_type())) {

Review comment:
       Lol! indeed! :open_mouth: 




-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: github-unsubscribe@arrow.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org