!9687 Adding AddChild functionality to SamplerObj

From: @mahdirahmanihanzaki
Reviewed-by: 
Signed-off-by:

mindspore/ccsrc/minddata/dataset/api/samplers.cc

@@ -48,6 +48,34 @@ namespace dataset {
 // Constructor
 SamplerObj::SamplerObj() {}
 
+void SamplerObj::BuildChildren(std::shared_ptr<SamplerRT> sampler) {
+  for (auto child : children_) {
+    auto sampler_rt = child->Build();
+    sampler->AddChild(sampler_rt);
+  }
+}
+
+Status SamplerObj::AddChild(std::shared_ptr<SamplerObj> child) {
+  if (child == nullptr) {
+    return Status::OK();
+  }
+
+  // Only samplers can be added, not any other DatasetOp.
+  std::shared_ptr<SamplerObj> sampler = std::dynamic_pointer_cast<SamplerObj>(child);
+  if (!sampler) {
+    RETURN_STATUS_UNEXPECTED("Cannot add child, child is not a sampler object.");
+  }
+
+  // Samplers can have at most 1 child.
+  if (!children_.empty()) {
+    RETURN_STATUS_UNEXPECTED("Cannot add child sampler, this sampler already has a child.");
+  }
+
+  children_.push_back(child);
+
+  return Status::OK();
+}
+
 /// Function to create a Distributed Sampler.
 std::shared_ptr<DistributedSamplerObj> DistributedSampler(int64_t num_shards, int64_t shard_id, bool shuffle,
                                                           int64_t num_samples, uint32_t seed, int64_t offset,
@@ -55,7 +83,7 @@ std::shared_ptr<DistributedSamplerObj> DistributedSampler(int64_t num_shards, in
   auto sampler =
     std::make_shared<DistributedSamplerObj>(num_shards, shard_id, shuffle, num_samples, seed, offset, even_dist);
   // Input validation
-  if (!sampler->ValidateParams()) {
+  if (sampler->ValidateParams().IsError()) {
     return nullptr;
   }
   return sampler;
@@ -65,7 +93,7 @@ std::shared_ptr<DistributedSamplerObj> DistributedSampler(int64_t num_shards, in
 std::shared_ptr<PKSamplerObj> PKSampler(int64_t num_val, bool shuffle, int64_t num_samples) {
   auto sampler = std::make_shared<PKSamplerObj>(num_val, shuffle, num_samples);
   // Input validation
-  if (!sampler->ValidateParams()) {
+  if (sampler->ValidateParams().IsError()) {
     return nullptr;
   }
   return sampler;
@@ -75,7 +103,7 @@ std::shared_ptr<PKSamplerObj> PKSampler(int64_t num_val, bool shuffle, int64_t n
 std::shared_ptr<RandomSamplerObj> RandomSampler(bool replacement, int64_t num_samples) {
   auto sampler = std::make_shared<RandomSamplerObj>(replacement, num_samples);
   // Input validation
-  if (!sampler->ValidateParams()) {
+  if (sampler->ValidateParams().IsError()) {
     return nullptr;
   }
   return sampler;
@@ -85,7 +113,7 @@ std::shared_ptr<RandomSamplerObj> RandomSampler(bool replacement, int64_t num_sa
 std::shared_ptr<SequentialSamplerObj> SequentialSampler(int64_t start_index, int64_t num_samples) {
   auto sampler = std::make_shared<SequentialSamplerObj>(start_index, num_samples);
   // Input validation
-  if (!sampler->ValidateParams()) {
+  if (sampler->ValidateParams().IsError()) {
     return nullptr;
   }
   return sampler;
@@ -95,7 +123,7 @@ std::shared_ptr<SequentialSamplerObj> SequentialSampler(int64_t start_index, int
 std::shared_ptr<SubsetRandomSamplerObj> SubsetRandomSampler(std::vector<int64_t> indices, int64_t num_samples) {
   auto sampler = std::make_shared<SubsetRandomSamplerObj>(std::move(indices), num_samples);
   // Input validation
-  if (!sampler->ValidateParams()) {
+  if (sampler->ValidateParams().IsError()) {
     return nullptr;
   }
   return sampler;
@@ -106,7 +134,7 @@ std::shared_ptr<WeightedRandomSamplerObj> WeightedRandomSampler(std::vector<doub
                                                                 bool replacement) {
   auto sampler = std::make_shared<WeightedRandomSamplerObj>(std::move(weights), num_samples, replacement);
   // Input validation
-  if (!sampler->ValidateParams()) {
+  if (sampler->ValidateParams().IsError()) {
     return nullptr;
   }
   return sampler;
@@ -131,35 +159,33 @@ DistributedSamplerObj::DistributedSamplerObj(int64_t num_shards, int64_t shard_i
   GlobalContext::config_manager()->set_num_shards_for_auto_num_workers(num_shards_);
 }
 
-bool DistributedSamplerObj::ValidateParams() {
+Status DistributedSamplerObj::ValidateParams() {
   if (num_shards_ <= 0) {
-    MS_LOG(ERROR) << "DistributedSampler: invalid num_shards: " << num_shards_;
-    return false;
+    RETURN_STATUS_UNEXPECTED("DistributedSampler: invalid num_shards: " + std::to_string(num_shards_));
   }
 
   if (shard_id_ < 0 || shard_id_ >= num_shards_) {
-    MS_LOG(ERROR) << "DistributedSampler: invalid input, shard_id: " << shard_id_ << ", num_shards: " << num_shards_;
-    return false;
+    RETURN_STATUS_UNEXPECTED("DistributedSampler: invalid input, shard_id: " + std::to_string(shard_id_) +
+                             ", num_shards: " + std::to_string(num_shards_));
   }
 
   if (num_samples_ < 0) {
-    MS_LOG(ERROR) << "DistributedSampler: invalid num_samples: " << num_samples_;
-    return false;
+    RETURN_STATUS_UNEXPECTED("DistributedSampler: invalid num_samples: " + std::to_string(num_samples_));
   }
 
   if (offset_ > num_shards_) {
-    MS_LOG(ERROR) << "DistributedSampler: invalid offset: " << offset_
-                  << ", which should be no more than num_shards: " << num_shards_;
-    return false;
+    RETURN_STATUS_UNEXPECTED("DistributedSampler: invalid offset: " + std::to_string(offset_) +
+                             ", which should be no more than num_shards: " + std::to_string(num_shards_));
   }
 
-  return true;
+  return Status::OK();
 }
 
 std::shared_ptr<SamplerRT> DistributedSamplerObj::Build() {
   // runtime sampler object
   auto sampler = std::make_shared<dataset::DistributedSamplerRT>(num_samples_, num_shards_, shard_id_, shuffle_, seed_,
                                                                  offset_, even_dist_);
+  BuildChildren(sampler);
   return sampler;
 }
 
@@ -176,23 +202,21 @@ std::shared_ptr<mindrecord::ShardOperator> DistributedSamplerObj::BuildForMindDa
 PKSamplerObj::PKSamplerObj(int64_t num_val, bool shuffle, int64_t num_samples)
     : num_val_(num_val), shuffle_(shuffle), num_samples_(num_samples) {}
 
-bool PKSamplerObj::ValidateParams() {
+Status PKSamplerObj::ValidateParams() {
   if (num_val_ <= 0) {
-    MS_LOG(ERROR) << "PKSampler: invalid num_val: " << num_val_;
-    return false;
+    RETURN_STATUS_UNEXPECTED("PKSampler: invalid num_val: " + std::to_string(num_val_));
   }
 
   if (num_samples_ < 0) {
-    MS_LOG(ERROR) << "PKSampler: invalid num_samples: " << num_samples_;
-    return false;
+    RETURN_STATUS_UNEXPECTED("PKSampler: invalid num_samples: " + std::to_string(num_samples_));
   }
-  return true;
+  return Status::OK();
 }
 
 std::shared_ptr<SamplerRT> PKSamplerObj::Build() {
   // runtime sampler object
   auto sampler = std::make_shared<dataset::PKSamplerRT>(num_samples_, num_val_, shuffle_);
-
+  BuildChildren(sampler);
   return sampler;
 }
 
@@ -204,9 +228,12 @@ PreBuiltSamplerObj::PreBuiltSamplerObj(std::shared_ptr<mindrecord::ShardOperator
     : sp_minddataset_(std::move(sampler)) {}
 #endif
 
-bool PreBuiltSamplerObj::ValidateParams() { return true; }
+Status PreBuiltSamplerObj::ValidateParams() { return Status::OK(); }
 
-std::shared_ptr<SamplerRT> PreBuiltSamplerObj::Build() { return sp_; }
+std::shared_ptr<SamplerRT> PreBuiltSamplerObj::Build() {
+  BuildChildren(sp_);
+  return sp_;
+}
 
 #ifndef ENABLE_ANDROID
 std::shared_ptr<mindrecord::ShardOperator> PreBuiltSamplerObj::BuildForMindDataset() { return sp_minddataset_; }
@@ -214,9 +241,19 @@ std::shared_ptr<mindrecord::ShardOperator> PreBuiltSamplerObj::BuildForMindDatas
 
 std::shared_ptr<SamplerObj> PreBuiltSamplerObj::Copy() {
 #ifndef ENABLE_ANDROID
-  if (sp_minddataset_ != nullptr) return std::make_shared<PreBuiltSamplerObj>(sp_minddataset_);
+  if (sp_minddataset_ != nullptr) {
+    auto sampler = std::make_shared<PreBuiltSamplerObj>(sp_minddataset_);
+    for (auto child : children_) {
+      sampler->AddChild(child);
+    }
+    return sampler;
+  }
 #endif
-  return std::make_shared<PreBuiltSamplerObj>(sp_);
+  auto sampler = std::make_shared<PreBuiltSamplerObj>(sp_);
+  for (auto child : children_) {
+    sampler->AddChild(child);
+  }
+  return sampler;
 }
 
 #ifndef ENABLE_ANDROID
@@ -238,19 +275,18 @@ std::shared_ptr<mindrecord::ShardOperator> PKSamplerObj::BuildForMindDataset() {
 RandomSamplerObj::RandomSamplerObj(bool replacement, int64_t num_samples)
     : replacement_(replacement), num_samples_(num_samples) {}
 
-bool RandomSamplerObj::ValidateParams() {
+Status RandomSamplerObj::ValidateParams() {
   if (num_samples_ < 0) {
-    MS_LOG(ERROR) << "RandomSampler: invalid num_samples: " << num_samples_;
-    return false;
+    RETURN_STATUS_UNEXPECTED("RandomSampler: invalid num_samples: " + std::to_string(num_samples_));
   }
-  return true;
+  return Status::OK();
 }
 
 std::shared_ptr<SamplerRT> RandomSamplerObj::Build() {
   // runtime sampler object
   bool reshuffle_each_epoch = true;
   auto sampler = std::make_shared<dataset::RandomSamplerRT>(num_samples_, replacement_, reshuffle_each_epoch);
-
+  BuildChildren(sampler);
   return sampler;
 }
 
@@ -269,24 +305,22 @@ std::shared_ptr<mindrecord::ShardOperator> RandomSamplerObj::BuildForMindDataset
 SequentialSamplerObj::SequentialSamplerObj(int64_t start_index, int64_t num_samples)
     : start_index_(start_index), num_samples_(num_samples) {}
 
-bool SequentialSamplerObj::ValidateParams() {
+Status SequentialSamplerObj::ValidateParams() {
   if (num_samples_ < 0) {
-    MS_LOG(ERROR) << "SequentialSampler: invalid num_samples: " << num_samples_;
-    return false;
+    RETURN_STATUS_UNEXPECTED("SequentialSampler: invalid num_samples: " + std::to_string(num_samples_));
   }
 
   if (start_index_ < 0) {
-    MS_LOG(ERROR) << "SequentialSampler: invalid start_index: " << start_index_;
-    return false;
+    RETURN_STATUS_UNEXPECTED("SequentialSampler: invalid start_index: " + std::to_string(start_index_));
   }
 
-  return true;
+  return Status::OK();
 }
 
 std::shared_ptr<SamplerRT> SequentialSamplerObj::Build() {
   // runtime sampler object
   auto sampler = std::make_shared<dataset::SequentialSamplerRT>(num_samples_, start_index_);
-
+  BuildChildren(sampler);
   return sampler;
 }
 
@@ -303,19 +337,18 @@ std::shared_ptr<mindrecord::ShardOperator> SequentialSamplerObj::BuildForMindDat
 SubsetRandomSamplerObj::SubsetRandomSamplerObj(std::vector<int64_t> indices, int64_t num_samples)
     : indices_(std::move(indices)), num_samples_(num_samples) {}
 
-bool SubsetRandomSamplerObj::ValidateParams() {
+Status SubsetRandomSamplerObj::ValidateParams() {
   if (num_samples_ < 0) {
-    MS_LOG(ERROR) << "SubsetRandomSampler: invalid num_samples: " << num_samples_;
-    return false;
+    RETURN_STATUS_UNEXPECTED("SubsetRandomSampler: invalid num_samples: " + std::to_string(num_samples_));
   }
 
-  return true;
+  return Status::OK();
 }
 
 std::shared_ptr<SamplerRT> SubsetRandomSamplerObj::Build() {
   // runtime sampler object
   auto sampler = std::make_shared<dataset::SubsetRandomSamplerRT>(num_samples_, indices_);
-
+  BuildChildren(sampler);
   return sampler;
 }
 
@@ -332,34 +365,32 @@ std::shared_ptr<mindrecord::ShardOperator> SubsetRandomSamplerObj::BuildForMindD
 WeightedRandomSamplerObj::WeightedRandomSamplerObj(std::vector<double> weights, int64_t num_samples, bool replacement)
     : weights_(std::move(weights)), num_samples_(num_samples), replacement_(replacement) {}
 
-bool WeightedRandomSamplerObj::ValidateParams() {
+Status WeightedRandomSamplerObj::ValidateParams() {
   if (weights_.empty()) {
-    MS_LOG(ERROR) << "WeightedRandomSampler: weights vector must not be empty";
-    return false;
+    RETURN_STATUS_UNEXPECTED("WeightedRandomSampler: weights vector must not be empty");
   }
   int32_t zero_elem = 0;
   for (int32_t i = 0; i < weights_.size(); ++i) {
     if (weights_[i] < 0) {
-      MS_LOG(ERROR) << "WeightedRandomSampler: weights vector must not contain negative number, got: " << weights_[i];
-      return false;
+      RETURN_STATUS_UNEXPECTED("WeightedRandomSampler: weights vector must not contain negative number, got: " +
+                               std::to_string(weights_[i]));
     }
     if (weights_[i] == 0.0) {
       zero_elem++;
     }
   }
   if (zero_elem == weights_.size()) {
-    MS_LOG(ERROR) << "WeightedRandomSampler: elements of weights vector must not be all zero";
-    return false;
+    RETURN_STATUS_UNEXPECTED("WeightedRandomSampler: elements of weights vector must not be all zero");
   }
   if (num_samples_ < 0) {
-    MS_LOG(ERROR) << "WeightedRandomSampler: invalid num_samples: " << num_samples_;
-    return false;
+    RETURN_STATUS_UNEXPECTED("WeightedRandomSampler: invalid num_samples: " + std::to_string(num_samples_));
   }
-  return true;
+  return Status::OK();
 }
 
 std::shared_ptr<SamplerRT> WeightedRandomSamplerObj::Build() {
   auto sampler = std::make_shared<dataset::WeightedRandomSamplerRT>(num_samples_, weights_, replacement_);
+  BuildChildren(sampler);
   return sampler;
 }
 

mindspore/ccsrc/minddata/dataset/engine/datasetops/source/sampler/distributed_sampler.cc

@@ -43,6 +43,9 @@ DistributedSamplerRT::DistributedSamplerRT(int64_t num_samples, int64_t num_dev,
 }
 
 Status DistributedSamplerRT::InitSampler() {
+  if (is_initialized) {
+    return Status::OK();
+  }
   // Special value of 0 for num_samples means that the user wants to sample the entire set of data.
   // If the user asked to sample more rows than exists in the dataset, adjust the num_samples accordingly.
   if (num_samples_ == 0 || num_samples_ > num_rows_) {
@@ -78,6 +81,7 @@ Status DistributedSamplerRT::InitSampler() {
   }
   if (!samples_per_buffer_) non_empty_ = false;
 
+  is_initialized = true;
   return Status::OK();
 }
 

mindspore/ccsrc/minddata/dataset/engine/datasetops/source/sampler/pk_sampler.cc

@@ -28,6 +28,9 @@ PKSamplerRT::PKSamplerRT(int64_t num_samples, int64_t val, bool shuffle, int64_t
       samples_per_class_(val) {}
 
 Status PKSamplerRT::InitSampler() {
+  if (is_initialized) {
+    return Status::OK();
+  }
   labels_.reserve(label_to_ids_.size());
   for (const auto &pair : label_to_ids_) {
     if (!pair.second.empty()) {
@@ -58,6 +61,7 @@ Status PKSamplerRT::InitSampler() {
   CHECK_FAIL_RETURN_UNEXPECTED(
     num_samples_ > 0, "Invalid parameter, num_class or K (num samples per class) must be greater than 0, but got " +
                         std::to_string(num_samples_));
+  is_initialized = true;
   return Status::OK();
 }
 

mindspore/ccsrc/minddata/dataset/engine/datasetops/source/sampler/python_sampler.cc

@@ -65,6 +65,9 @@ Status PythonSamplerRT::GetNextSample(std::unique_ptr<DataBuffer> *out_buffer) {
 }
 
 Status PythonSamplerRT::InitSampler() {
+  if (is_initialized) {
+    return Status::OK();
+  }
   CHECK_FAIL_RETURN_UNEXPECTED(
     num_rows_ > 0, "Invalid parameter, num_rows must be greater than 0, but got " + std::to_string(num_rows_));
   // Special value of 0 for num_samples means that the user wants to sample the entire set of data.
@@ -83,6 +86,8 @@ Status PythonSamplerRT::InitSampler() {
       return Status(StatusCode::kPyFuncException, e.what());
     }
   }
+
+  is_initialized = true;
   return Status::OK();
 }
 

mindspore/ccsrc/minddata/dataset/engine/datasetops/source/sampler/random_sampler.cc

@@ -69,6 +69,9 @@ Status RandomSamplerRT::GetNextSample(std::unique_ptr<DataBuffer> *out_buffer) {
 }
 
 Status RandomSamplerRT::InitSampler() {
+  if (is_initialized) {
+    return Status::OK();
+  }
   // Special value of 0 for num_samples means that the user wants to sample the entire set of data.
   // If the user asked to sample more rows than exists in the dataset, adjust the num_samples accordingly.
   if (num_samples_ == 0 || num_samples_ > num_rows_) {
@@ -91,6 +94,7 @@ Status RandomSamplerRT::InitSampler() {
     dist = std::make_unique<std::uniform_int_distribution<int64_t>>(0, num_rows_ - 1);
   }
 
+  is_initialized = true;
   return Status::OK();
 }
 

mindspore/ccsrc/minddata/dataset/engine/datasetops/source/sampler/sampler.cc

@@ -34,7 +34,11 @@ Status RandomAccessOp::GetNumRowsInDataset(int64_t *num) const {
 }
 
 SamplerRT::SamplerRT(int64_t num_samples, int64_t samples_per_buffer)
-    : num_rows_(0), num_samples_(num_samples), samples_per_buffer_(samples_per_buffer), col_desc_(nullptr) {}
+    : num_rows_(0),
+      num_samples_(num_samples),
+      samples_per_buffer_(samples_per_buffer),
+      col_desc_(nullptr),
+      is_initialized(false) {}
 
 Status SamplerRT::HandshakeRandomAccessOp(const RandomAccessOp *op) {
   std::shared_ptr<SamplerRT> child_sampler;

mindspore/ccsrc/minddata/dataset/engine/datasetops/source/sampler/sampler.h

@@ -160,6 +160,7 @@ class SamplerRT {
   // amount.
   int64_t num_samples_;
 
+  bool is_initialized;
   int64_t samples_per_buffer_;
   std::unique_ptr<ColDescriptor> col_desc_;
   std::vector<std::shared_ptr<SamplerRT>> child_;  // Child nodes

mindspore/ccsrc/minddata/dataset/engine/datasetops/source/sampler/sequential_sampler.cc

@@ -63,6 +63,9 @@ Status SequentialSamplerRT::GetNextSample(std::unique_ptr<DataBuffer> *out_buffe
 }
 
 Status SequentialSamplerRT::InitSampler() {
+  if (is_initialized) {
+    return Status::OK();
+  }
   CHECK_FAIL_RETURN_UNEXPECTED(start_index_ >= 0,
                                "Invalid parameter, start_index must be greater than or equal to 0, but got " +
                                  std::to_string(start_index_) + ".\n");
@@ -82,6 +85,8 @@ Status SequentialSamplerRT::InitSampler() {
     num_samples_ > 0 && samples_per_buffer_ > 0,
     "Invalid parameter, samples_per_buffer must be greater than 0, but got " + std::to_string(samples_per_buffer_));
   samples_per_buffer_ = samples_per_buffer_ > num_samples_ ? num_samples_ : samples_per_buffer_;
+
+  is_initialized = true;
   return Status::OK();
 }
 

mindspore/ccsrc/minddata/dataset/engine/datasetops/source/sampler/subset_random_sampler.cc

@@ -32,6 +32,9 @@ SubsetRandomSamplerRT::SubsetRandomSamplerRT(int64_t num_samples, const std::vec
 
 // Initialized this Sampler.
 Status SubsetRandomSamplerRT::InitSampler() {
+  if (is_initialized) {
+    return Status::OK();
+  }
   CHECK_FAIL_RETURN_UNEXPECTED(
     num_rows_ > 0, "Invalid parameter, num_rows must be greater than 0, but got " + std::to_string(num_rows_) + ".\n");
 
@@ -51,6 +54,7 @@ Status SubsetRandomSamplerRT::InitSampler() {
   // We will shuffle the full set of id's, but only select the first num_samples_ of them later.
   std::shuffle(indices_.begin(), indices_.end(), rand_gen_);
 
+  is_initialized = true;
   return Status::OK();
 }
 

mindspore/ccsrc/minddata/dataset/engine/datasetops/source/sampler/weighted_random_sampler.cc

@@ -37,6 +37,9 @@ WeightedRandomSamplerRT::WeightedRandomSamplerRT(int64_t num_samples, const std:
 
 // Initialized this Sampler.
 Status WeightedRandomSamplerRT::InitSampler() {
+  if (is_initialized) {
+    return Status::OK();
+  }
   // Special value of 0 for num_samples means that the user wants to sample the entire set of data.
   // If the user asked to sample more rows than exists in the dataset, adjust the num_samples accordingly.
   if (num_samples_ == 0 || num_samples_ > num_rows_) {
@@ -75,6 +78,7 @@ Status WeightedRandomSamplerRT::InitSampler() {
     discrete_dist_ = std::make_unique<std::discrete_distribution<int64_t>>(weights_.begin(), weights_.end());
   }
 
+  is_initialized = true;
   return Status::OK();
 }
 

mindspore/ccsrc/minddata/dataset/include/samplers.h

@@ -22,7 +22,10 @@
 #include <vector>
 
 #ifndef ENABLE_ANDROID
-#include "minddata/dataset/engine/datasetops/source/mindrecord_op.h"
+#include "minddata/dataset/util/status.h"
+#include "minddata/mindrecord/include/shard_column.h"
+#include "minddata/mindrecord/include/shard_error.h"
+#include "minddata/mindrecord/include/shard_reader.h"
 #endif
 
 namespace mindspore {
@@ -40,8 +43,8 @@ class SamplerObj : public std::enable_shared_from_this<SamplerObj> {
   ~SamplerObj() = default;
 
   /// \brief Pure virtual function for derived class to implement parameters validation
-  /// \return bool true if all the parameters are valid
-  virtual bool ValidateParams() = 0;
+  /// \return The Status code of the function. It returns OK status if parameters are valid.
+  virtual Status ValidateParams() = 0;
 
   /// \brief Pure virtual function to convert a SamplerObj class into a runtime sampler object
   /// \return Shared pointers to the newly created Sampler
@@ -55,12 +58,24 @@ class SamplerObj : public std::enable_shared_from_this<SamplerObj> {
   /// \return The shard id of the derived sampler
   virtual int64_t ShardId() { return 0; }
 
+  /// \brief Adds a child to the sampler
+  /// \param[in] child The sampler to be added as child
+  /// \return the Status code returned
+  Status AddChild(std::shared_ptr<SamplerObj> child);
+
 #ifndef ENABLE_ANDROID
   /// \brief Virtual function to convert a SamplerObj class into a runtime mindrecord sampler object,
   ///     only override by SubsetRandomSampler, PkSampler, RandomSampler, SequentialSampler, DistributedSampler
   /// \return Shared pointers to the newly created Sampler
   virtual std::shared_ptr<mindrecord::ShardOperator> BuildForMindDataset() { return nullptr; }
 #endif
+
+ protected:
+  /// \brief A function that calls build on the children of this sampler
+  /// \param[in] sampler The samplerRT object built from this sampler
+  void BuildChildren(std::shared_ptr<SamplerRT> sampler);
+
+  std::vector<std::shared_ptr<SamplerObj>> children_;
 };
 
 class DistributedSamplerObj;
@@ -137,15 +152,19 @@ class DistributedSamplerObj : public SamplerObj {
   std::shared_ptr<SamplerRT> Build() override;
 
   std::shared_ptr<SamplerObj> Copy() override {
-    return std::make_shared<DistributedSamplerObj>(num_shards_, shard_id_, shuffle_, num_samples_, seed_, offset_,
-                                                   even_dist_);
+    auto sampler = std::make_shared<DistributedSamplerObj>(num_shards_, shard_id_, shuffle_, num_samples_, seed_,
+                                                           offset_, even_dist_);
+    for (auto child : children_) {
+      sampler->AddChild(child);
+    }
+    return sampler;
   }
 
 #ifndef ENABLE_ANDROID
   std::shared_ptr<mindrecord::ShardOperator> BuildForMindDataset() override;
 #endif
 
-  bool ValidateParams() override;
+  Status ValidateParams() override;
 
   /// \brief Function to get the shard id of sampler
   /// \return The shard id of sampler
@@ -170,14 +189,18 @@ class PKSamplerObj : public SamplerObj {
   std::shared_ptr<SamplerRT> Build() override;
 
   std::shared_ptr<SamplerObj> Copy() override {
-    return std::make_shared<PKSamplerObj>(num_val_, shuffle_, num_samples_);
+    auto sampler = std::make_shared<PKSamplerObj>(num_val_, shuffle_, num_samples_);
+    for (auto child : children_) {
+      sampler->AddChild(child);
+    }
+    return sampler;
   }
 
 #ifndef ENABLE_ANDROID
   std::shared_ptr<mindrecord::ShardOperator> BuildForMindDataset() override;
 #endif
 
-  bool ValidateParams() override;
+  Status ValidateParams() override;
 
  private:
   int64_t num_val_;
@@ -202,7 +225,7 @@ class PreBuiltSamplerObj : public SamplerObj {
 
   std::shared_ptr<SamplerObj> Copy() override;
 
-  bool ValidateParams() override;
+  Status ValidateParams() override;
 
  private:
   std::shared_ptr<SamplerRT> sp_;
@@ -219,13 +242,19 @@ class RandomSamplerObj : public SamplerObj {
 
   std::shared_ptr<SamplerRT> Build() override;
 
-  std::shared_ptr<SamplerObj> Copy() override { return std::make_shared<RandomSamplerObj>(replacement_, num_samples_); }
+  std::shared_ptr<SamplerObj> Copy() override {
+    auto sampler = std::make_shared<RandomSamplerObj>(replacement_, num_samples_);
+    for (auto child : children_) {
+      sampler->AddChild(child);
+    }
+    return sampler;
+  }
 
 #ifndef ENABLE_ANDROID
   std::shared_ptr<mindrecord::ShardOperator> BuildForMindDataset() override;
 #endif
 
-  bool ValidateParams() override;
+  Status ValidateParams() override;
 
  private:
   bool replacement_;
@@ -241,14 +270,18 @@ class SequentialSamplerObj : public SamplerObj {
   std::shared_ptr<SamplerRT> Build() override;
 
   std::shared_ptr<SamplerObj> Copy() override {
-    return std::make_shared<SequentialSamplerObj>(start_index_, num_samples_);
+    auto sampler = std::make_shared<SequentialSamplerObj>(start_index_, num_samples_);
+    for (auto child : children_) {
+      sampler->AddChild(child);
+    }
+    return sampler;
   }
 
 #ifndef ENABLE_ANDROID
   std::shared_ptr<mindrecord::ShardOperator> BuildForMindDataset() override;
 #endif
 
-  bool ValidateParams() override;
+  Status ValidateParams() override;
 
  private:
   int64_t start_index_;
@@ -264,14 +297,18 @@ class SubsetRandomSamplerObj : public SamplerObj {
   std::shared_ptr<SamplerRT> Build() override;
 
   std::shared_ptr<SamplerObj> Copy() override {
-    return std::make_shared<SubsetRandomSamplerObj>(indices_, num_samples_);
+    auto sampler = std::make_shared<SubsetRandomSamplerObj>(indices_, num_samples_);
+    for (auto child : children_) {
+      sampler->AddChild(child);
+    }
+    return sampler;
   }
 
 #ifndef ENABLE_ANDROID
   std::shared_ptr<mindrecord::ShardOperator> BuildForMindDataset() override;
 #endif
 
-  bool ValidateParams() override;
+  Status ValidateParams() override;
 
  private:
   const std::vector<int64_t> indices_;
@@ -287,10 +324,14 @@ class WeightedRandomSamplerObj : public SamplerObj {
   std::shared_ptr<SamplerRT> Build() override;
 
   std::shared_ptr<SamplerObj> Copy() override {
-    return std::make_shared<WeightedRandomSamplerObj>(weights_, num_samples_, replacement_);
+    auto sampler = std::make_shared<WeightedRandomSamplerObj>(weights_, num_samples_, replacement_);
+    for (auto child : children_) {
+      sampler->AddChild(child);
+    }
+    return sampler;
   }
 
-  bool ValidateParams() override;
+  Status ValidateParams() override;
 
  private:
   const std::vector<double> weights_;

tests/ut/cpp/dataset/c_api_samplers_test.cc

@@ -208,6 +208,37 @@ TEST_F(MindDataTestPipeline, TestDistributedSamplerSuccess) {
   iter->Stop();
 }
 
+TEST_F(MindDataTestPipeline, TestSamplerAddChild) {
+  MS_LOG(INFO) << "Doing MindDataTestPipeline-TestSamplerAddChild.";
+
+  auto sampler = DistributedSampler(1, 0, false, 5, 0, -1, true);
+  EXPECT_NE(sampler, nullptr);
+
+  auto child_sampler = SequentialSampler();
+  sampler->AddChild(child_sampler);
+  EXPECT_NE(child_sampler, nullptr);
+
+  // Create an ImageFolder Dataset
+  std::string folder_path = datasets_root_path_ + "/testPK/data/";
+  std::shared_ptr<Dataset> ds = ImageFolder(folder_path, false, sampler);
+  EXPECT_NE(ds, nullptr);
+
+  // Iterate the dataset and get each row
+  std::shared_ptr<Iterator> iter = ds->CreateIterator();
+  EXPECT_NE(iter, nullptr);
+  std::unordered_map<std::string, std::shared_ptr<Tensor>> row;
+  iter->GetNextRow(&row);
+
+  uint64_t i = 0;
+  while (row.size() != 0) {
+    i++;
+    iter->GetNextRow(&row);
+  }
+
+  EXPECT_EQ(ds->GetDatasetSize(), 5);
+  iter->Stop();
+}
+
 TEST_F(MindDataTestPipeline, TestDistributedSamplerFail) {
   MS_LOG(INFO) << "Doing MindDataTestPipeline-TestDistributedSamplerFail.";
   // Test invalid offset setting of distributed_sampler