1 files changed, 85 insertions, 0 deletions
diff --git a/src/rocksdb/db/merge_operator.cc b/src/rocksdb/db/merge_operator.cc
new file mode 100644
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+++ b/src/rocksdb/db/merge_operator.cc
@@ -0,0 +1,85 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+/**
+ * Back-end implementation details specific to the Merge Operator.
+ */
+
+#include "rocksdb/merge_operator.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+bool MergeOperator::FullMergeV2(const MergeOperationInput& merge_in,
+                                MergeOperationOutput* merge_out) const {
+  // If FullMergeV2 is not implemented, we convert the operand_list to
+  // std::deque<std::string> and pass it to FullMerge
+  std::deque<std::string> operand_list_str;
+  for (auto& op : merge_in.operand_list) {
+    operand_list_str.emplace_back(op.data(), op.size());
+  }
+  return FullMerge(merge_in.key, merge_in.existing_value, operand_list_str,
+                   &merge_out->new_value, merge_in.logger);
+}
+
+// The default implementation of PartialMergeMulti, which invokes
+// PartialMerge multiple times internally and merges two operands at
+// a time.
+bool MergeOperator::PartialMergeMulti(const Slice& key,
+                                      const std::deque<Slice>& operand_list,
+                                      std::string* new_value,
+                                      Logger* logger) const {
+  assert(operand_list.size() >= 2);
+  // Simply loop through the operands
+  Slice temp_slice(operand_list[0]);
+
+  for (size_t i = 1; i < operand_list.size(); ++i) {
+    auto& operand = operand_list[i];
+    std::string temp_value;
+    if (!PartialMerge(key, temp_slice, operand, &temp_value, logger)) {
+      return false;
+    }
+    swap(temp_value, *new_value);
+    temp_slice = Slice(*new_value);
+  }
+
+  // The result will be in *new_value. All merges succeeded.
+  return true;
+}
+
+// Given a "real" merge from the library, call the user's
+// associative merge function one-by-one on each of the operands.
+// NOTE: It is assumed that the client's merge-operator will handle any errors.
+bool AssociativeMergeOperator::FullMergeV2(
+    const MergeOperationInput& merge_in,
+    MergeOperationOutput* merge_out) const {
+  // Simply loop through the operands
+  Slice temp_existing;
+  const Slice* existing_value = merge_in.existing_value;
+  for (const auto& operand : merge_in.operand_list) {
+    std::string temp_value;
+    if (!Merge(merge_in.key, existing_value, operand, &temp_value,
+               merge_in.logger)) {
+      return false;
+    }
+    swap(temp_value, merge_out->new_value);
+    temp_existing = Slice(merge_out->new_value);
+    existing_value = &temp_existing;
+  }
+
+  // The result will be in *new_value. All merges succeeded.
+  return true;
+}
+
+// Call the user defined simple merge on the operands;
+// NOTE: It is assumed that the client's merge-operator will handle any errors.
+bool AssociativeMergeOperator::PartialMerge(const Slice& key,
+                                            const Slice& left_operand,
+                                            const Slice& right_operand,
+                                            std::string* new_value,
+                                            Logger* logger) const {
+  return Merge(key, &left_operand, right_operand, new_value, logger);
+}
+
+}  // namespace ROCKSDB_NAMESPACE