1 files changed, 132 insertions, 0 deletions
diff --git a/src/rocksdb/utilities/merge_operators/string_append/stringappend2.cc b/src/rocksdb/utilities/merge_operators/string_append/stringappend2.cc
new file mode 100644
index 000000000..36cb9ee34
--- /dev/null
+++ b/src/rocksdb/utilities/merge_operators/string_append/stringappend2.cc
@@ -0,0 +1,132 @@
+/**
+ * @author Deon Nicholas (dnicholas@fb.com)
+ * Copyright 2013 Facebook
+ */
+
+#include "stringappend2.h"
+
+#include <assert.h>
+
+#include <memory>
+#include <string>
+
+#include "rocksdb/merge_operator.h"
+#include "rocksdb/slice.h"
+#include "rocksdb/utilities/options_type.h"
+#include "utilities/merge_operators.h"
+
+namespace ROCKSDB_NAMESPACE {
+namespace {
+static std::unordered_map<std::string, OptionTypeInfo>
+    stringappend2_merge_type_info = {
+#ifndef ROCKSDB_LITE
+        {"delimiter",
+         {0, OptionType::kString, OptionVerificationType::kNormal,
+          OptionTypeFlags::kNone}},
+#endif  // ROCKSDB_LITE
+};
+}  // namespace
+
+// Constructor: also specify the delimiter character.
+StringAppendTESTOperator::StringAppendTESTOperator(char delim_char)
+    : delim_(1, delim_char) {
+  RegisterOptions("Delimiter", &delim_, &stringappend2_merge_type_info);
+}
+
+StringAppendTESTOperator::StringAppendTESTOperator(const std::string& delim)
+    : delim_(delim) {
+  RegisterOptions("Delimiter", &delim_, &stringappend2_merge_type_info);
+}
+
+// Implementation for the merge operation (concatenates two strings)
+bool StringAppendTESTOperator::FullMergeV2(
+    const MergeOperationInput& merge_in,
+    MergeOperationOutput* merge_out) const {
+  // Clear the *new_value for writing.
+  merge_out->new_value.clear();
+
+  if (merge_in.existing_value == nullptr && merge_in.operand_list.size() == 1) {
+    // Only one operand
+    merge_out->existing_operand = merge_in.operand_list.back();
+    return true;
+  }
+
+  // Compute the space needed for the final result.
+  size_t numBytes = 0;
+
+  for (auto it = merge_in.operand_list.begin();
+       it != merge_in.operand_list.end(); ++it) {
+    numBytes += it->size() + delim_.size();
+  }
+
+  // Only print the delimiter after the first entry has been printed
+  bool printDelim = false;
+
+  // Prepend the *existing_value if one exists.
+  if (merge_in.existing_value) {
+    merge_out->new_value.reserve(numBytes + merge_in.existing_value->size());
+    merge_out->new_value.append(merge_in.existing_value->data(),
+                                merge_in.existing_value->size());
+    printDelim = true;
+  } else if (numBytes) {
+    // Without the existing (initial) value, the delimiter before the first of
+    // subsequent operands becomes redundant.
+    merge_out->new_value.reserve(numBytes - delim_.size());
+  }
+
+  // Concatenate the sequence of strings (and add a delimiter between each)
+  for (auto it = merge_in.operand_list.begin();
+       it != merge_in.operand_list.end(); ++it) {
+    if (printDelim) {
+      merge_out->new_value.append(delim_);
+    }
+    merge_out->new_value.append(it->data(), it->size());
+    printDelim = true;
+  }
+
+  return true;
+}
+
+bool StringAppendTESTOperator::PartialMergeMulti(
+    const Slice& /*key*/, const std::deque<Slice>& /*operand_list*/,
+    std::string* /*new_value*/, Logger* /*logger*/) const {
+  return false;
+}
+
+// A version of PartialMerge that actually performs "partial merging".
+// Use this to simulate the exact behaviour of the StringAppendOperator.
+bool StringAppendTESTOperator::_AssocPartialMergeMulti(
+    const Slice& /*key*/, const std::deque<Slice>& operand_list,
+    std::string* new_value, Logger* /*logger*/) const {
+  // Clear the *new_value for writing
+  assert(new_value);
+  new_value->clear();
+  assert(operand_list.size() >= 2);
+
+  // Generic append
+  // Determine and reserve correct size for *new_value.
+  size_t size = 0;
+  for (const auto& operand : operand_list) {
+    size += operand.size();
+  }
+  size += (operand_list.size() - 1) * delim_.length();  // Delimiters
+  new_value->reserve(size);
+
+  // Apply concatenation
+  new_value->assign(operand_list.front().data(), operand_list.front().size());
+
+  for (std::deque<Slice>::const_iterator it = operand_list.begin() + 1;
+       it != operand_list.end(); ++it) {
+    new_value->append(delim_);
+    new_value->append(it->data(), it->size());
+  }
+
+  return true;
+}
+
+std::shared_ptr<MergeOperator>
+MergeOperators::CreateStringAppendTESTOperator() {
+  return std::make_shared<StringAppendTESTOperator>(',');
+}
+
+}  // namespace ROCKSDB_NAMESPACE