arrow/array/builder_union.h

0001 // Licensed to the Apache Software Foundation (ASF) under one
0002 // or more contributor license agreements.  See the NOTICE file
0003 // distributed with this work for additional information
0004 // regarding copyright ownership.  The ASF licenses this file
0005 // to you under the Apache License, Version 2.0 (the
0006 // "License"); you may not use this file except in compliance
0007 // with the License.  You may obtain a copy of the License at
0008 //
0009 //   http://www.apache.org/licenses/LICENSE-2.0
0010 //
0011 // Unless required by applicable law or agreed to in writing,
0012 // software distributed under the License is distributed on an
0013 // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
0014 // KIND, either express or implied.  See the License for the
0015 // specific language governing permissions and limitations
0016 // under the License.
0017
0018 #pragma once
0019
0020 #include <cstdint>
0021 #include <memory>
0022 #include <string>
0023 #include <vector>
0024
0025 #include "arrow/array/array_nested.h"
0026 #include "arrow/array/builder_base.h"
0027 #include "arrow/array/data.h"
0028 #include "arrow/buffer_builder.h"
0029 #include "arrow/memory_pool.h"
0030 #include "arrow/status.h"
0031 #include "arrow/type.h"
0032 #include "arrow/util/visibility.h"
0033
0034 namespace arrow {
0035
0036 /// \addtogroup nested-builders
0037 ///
0038 /// @{
0039
0040 /// \brief Base class for union array builds.
0041 ///
0042 /// Note that while we subclass ArrayBuilder, as union types do not have a
0043 /// validity bitmap, the bitmap builder member of ArrayBuilder is not used.
0044 class ARROW_EXPORT BasicUnionBuilder : public ArrayBuilder {
0045  public:
0046   Status FinishInternal(std::shared_ptr<ArrayData>* out) override;
0047
0048   /// \cond FALSE
0049   using ArrayBuilder::Finish;
0050   /// \endcond
0051
0052   Status Finish(std::shared_ptr<UnionArray>* out) { return FinishTyped(out); }
0053
0054   /// \brief Make a new child builder available to the UnionArray
0055   ///
0056   /// \param[in] new_child the child builder
0057   /// \param[in] field_name the name of the field in the union array type
0058   /// if type inference is used
0059   /// \return child index, which is the "type" argument that needs
0060   /// to be passed to the "Append" method to add a new element to
0061   /// the union array.
0062   int8_t AppendChild(const std::shared_ptr<ArrayBuilder>& new_child,
0063                      const std::string& field_name = "");
0064
0065   std::shared_ptr<DataType> type() const override;
0066
0067   int64_t length() const override { return types_builder_.length(); }
0068
0069  protected:
0070   BasicUnionBuilder(MemoryPool* pool, int64_t alignment,
0071                     const std::vector<std::shared_ptr<ArrayBuilder>>& children,
0072                     const std::shared_ptr<DataType>& type);
0073
0074   int8_t NextTypeId();
0075
0076   std::vector<std::shared_ptr<Field>> child_fields_;
0077   std::vector<int8_t> type_codes_;
0078   UnionMode::type mode_;
0079
0080   std::vector<ArrayBuilder*> type_id_to_children_;
0081   std::vector<int> type_id_to_child_id_;
0082   // for all type_id < dense_type_id_, type_id_to_children_[type_id] != nullptr
0083   int8_t dense_type_id_ = 0;
0084   TypedBufferBuilder<int8_t> types_builder_;
0085 };
0086
0087 /// \class DenseUnionBuilder
0088 ///
0089 /// This API is EXPERIMENTAL.
0090 class ARROW_EXPORT DenseUnionBuilder : public BasicUnionBuilder {
0091  public:
0092   /// Use this constructor to initialize the UnionBuilder with no child builders,
0093   /// allowing type to be inferred. You will need to call AppendChild for each of the
0094   /// children builders you want to use.
0095   explicit DenseUnionBuilder(MemoryPool* pool,
0096                              int64_t alignment = kDefaultBufferAlignment)
0097       : BasicUnionBuilder(pool, alignment, {}, dense_union(FieldVector{})),
0098         offsets_builder_(pool, alignment) {}
0099
0100   /// Use this constructor to specify the type explicitly.
0101   /// You can still add child builders to the union after using this constructor
0102   DenseUnionBuilder(MemoryPool* pool,
0103                     const std::vector<std::shared_ptr<ArrayBuilder>>& children,
0104                     const std::shared_ptr<DataType>& type,
0105                     int64_t alignment = kDefaultBufferAlignment)
0106       : BasicUnionBuilder(pool, alignment, children, type),
0107         offsets_builder_(pool, alignment) {}
0108
0109   Status AppendNull() final {
0110     const int8_t first_child_code = type_codes_[0];
0111     ArrayBuilder* child_builder = type_id_to_children_[first_child_code];
0112     ARROW_RETURN_NOT_OK(types_builder_.Append(first_child_code));
0113     ARROW_RETURN_NOT_OK(
0114         offsets_builder_.Append(static_cast<int32_t>(child_builder->length())));
0115     // Append a null arbitrarily to the first child
0116     return child_builder->AppendNull();
0117   }
0118
0119   Status AppendNulls(int64_t length) final {
0120     const int8_t first_child_code = type_codes_[0];
0121     ArrayBuilder* child_builder = type_id_to_children_[first_child_code];
0122     ARROW_RETURN_NOT_OK(types_builder_.Append(length, first_child_code));
0123     ARROW_RETURN_NOT_OK(
0124         offsets_builder_.Append(length, static_cast<int32_t>(child_builder->length())));
0125     // Append just a single null to the first child
0126     return child_builder->AppendNull();
0127   }
0128
0129   Status AppendEmptyValue() final {
0130     const int8_t first_child_code = type_codes_[0];
0131     ArrayBuilder* child_builder = type_id_to_children_[first_child_code];
0132     ARROW_RETURN_NOT_OK(types_builder_.Append(first_child_code));
0133     ARROW_RETURN_NOT_OK(
0134         offsets_builder_.Append(static_cast<int32_t>(child_builder->length())));
0135     // Append an empty value arbitrarily to the first child
0136     return child_builder->AppendEmptyValue();
0137   }
0138
0139   Status AppendEmptyValues(int64_t length) final {
0140     const int8_t first_child_code = type_codes_[0];
0141     ArrayBuilder* child_builder = type_id_to_children_[first_child_code];
0142     ARROW_RETURN_NOT_OK(types_builder_.Append(length, first_child_code));
0143     ARROW_RETURN_NOT_OK(
0144         offsets_builder_.Append(length, static_cast<int32_t>(child_builder->length())));
0145     // Append just a single empty value to the first child
0146     return child_builder->AppendEmptyValue();
0147   }
0148
0149   /// \brief Append an element to the UnionArray. This must be followed
0150   ///        by an append to the appropriate child builder.
0151   ///
0152   /// \param[in] next_type type_id of the child to which the next value will be appended.
0153   ///
0154   /// The corresponding child builder must be appended to independently after this method
0155   /// is called.
0156   Status Append(int8_t next_type) {
0157     ARROW_RETURN_NOT_OK(types_builder_.Append(next_type));
0158     if (type_id_to_children_[next_type]->length() == kListMaximumElements) {
0159       return Status::CapacityError(
0160           "a dense UnionArray cannot contain more than 2^31 - 1 elements from a single "
0161           "child");
0162     }
0163     auto offset = static_cast<int32_t>(type_id_to_children_[next_type]->length());
0164     return offsets_builder_.Append(offset);
0165   }
0166
0167   Status AppendArraySlice(const ArraySpan& array, int64_t offset,
0168                           int64_t length) override;
0169
0170   Status FinishInternal(std::shared_ptr<ArrayData>* out) override;
0171
0172  private:
0173   TypedBufferBuilder<int32_t> offsets_builder_;
0174 };
0175
0176 /// \class SparseUnionBuilder
0177 ///
0178 /// This API is EXPERIMENTAL.
0179 class ARROW_EXPORT SparseUnionBuilder : public BasicUnionBuilder {
0180  public:
0181   /// Use this constructor to initialize the UnionBuilder with no child builders,
0182   /// allowing type to be inferred. You will need to call AppendChild for each of the
0183   /// children builders you want to use.
0184   explicit SparseUnionBuilder(MemoryPool* pool,
0185                               int64_t alignment = kDefaultBufferAlignment)
0186       : BasicUnionBuilder(pool, alignment, {}, sparse_union(FieldVector{})) {}
0187
0188   /// Use this constructor to specify the type explicitly.
0189   /// You can still add child builders to the union after using this constructor
0190   SparseUnionBuilder(MemoryPool* pool,
0191                      const std::vector<std::shared_ptr<ArrayBuilder>>& children,
0192                      const std::shared_ptr<DataType>& type,
0193                      int64_t alignment = kDefaultBufferAlignment)
0194       : BasicUnionBuilder(pool, alignment, children, type) {}
0195
0196   /// \brief Append a null value.
0197   ///
0198   /// A null is appended to the first child, empty values to the other children.
0199   Status AppendNull() final {
0200     const auto first_child_code = type_codes_[0];
0201     ARROW_RETURN_NOT_OK(types_builder_.Append(first_child_code));
0202     ARROW_RETURN_NOT_OK(type_id_to_children_[first_child_code]->AppendNull());
0203     for (int i = 1; i < static_cast<int>(type_codes_.size()); ++i) {
0204       ARROW_RETURN_NOT_OK(type_id_to_children_[type_codes_[i]]->AppendEmptyValue());
0205     }
0206     return Status::OK();
0207   }
0208
0209   /// \brief Append multiple null values.
0210   ///
0211   /// Nulls are appended to the first child, empty values to the other children.
0212   Status AppendNulls(int64_t length) final {
0213     const auto first_child_code = type_codes_[0];
0214     ARROW_RETURN_NOT_OK(types_builder_.Append(length, first_child_code));
0215     ARROW_RETURN_NOT_OK(type_id_to_children_[first_child_code]->AppendNulls(length));
0216     for (int i = 1; i < static_cast<int>(type_codes_.size()); ++i) {
0217       ARROW_RETURN_NOT_OK(
0218           type_id_to_children_[type_codes_[i]]->AppendEmptyValues(length));
0219     }
0220     return Status::OK();
0221   }
0222
0223   Status AppendEmptyValue() final {
0224     ARROW_RETURN_NOT_OK(types_builder_.Append(type_codes_[0]));
0225     for (int8_t code : type_codes_) {
0226       ARROW_RETURN_NOT_OK(type_id_to_children_[code]->AppendEmptyValue());
0227     }
0228     return Status::OK();
0229   }
0230
0231   Status AppendEmptyValues(int64_t length) final {
0232     ARROW_RETURN_NOT_OK(types_builder_.Append(length, type_codes_[0]));
0233     for (int8_t code : type_codes_) {
0234       ARROW_RETURN_NOT_OK(type_id_to_children_[code]->AppendEmptyValues(length));
0235     }
0236     return Status::OK();
0237   }
0238
0239   /// \brief Append an element to the UnionArray. This must be followed
0240   ///        by an append to the appropriate child builder.
0241   ///
0242   /// \param[in] next_type type_id of the child to which the next value will be appended.
0243   ///
0244   /// The corresponding child builder must be appended to independently after this method
0245   /// is called, and all other child builders must have null or empty value appended.
0246   Status Append(int8_t next_type) { return types_builder_.Append(next_type); }
0247
0248   Status AppendArraySlice(const ArraySpan& array, int64_t offset,
0249                           int64_t length) override;
0250 };
0251
0252 /// @}
0253
0254 }  // namespace arrow