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Diffstat (limited to '')
-rw-r--r-- | src/rocksdb/utilities/merge_operators/string_append/stringappend2.cc | 117 |
1 files changed, 117 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..b8c676ee5 --- /dev/null +++ b/src/rocksdb/utilities/merge_operators/string_append/stringappend2.cc @@ -0,0 +1,117 @@ +/** + * @author Deon Nicholas (dnicholas@fb.com) + * Copyright 2013 Facebook + */ + +#include "stringappend2.h" + +#include <memory> +#include <string> +#include <assert.h> + +#include "rocksdb/slice.h" +#include "rocksdb/merge_operator.h" +#include "utilities/merge_operators.h" + +namespace ROCKSDB_NAMESPACE { + +// Constructor: also specify the delimiter character. +StringAppendTESTOperator::StringAppendTESTOperator(char delim_char) + : delim_(delim_char) { +} + +// 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() + 1; // Plus 1 for the delimiter + } + + // 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) { + merge_out->new_value.reserve( + numBytes - 1); // Minus 1 since we have one less delimiter + } + + // 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(1, 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; // 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(1, delim_); + new_value->append(it->data(), it->size()); + } + + return true; +} + +const char* StringAppendTESTOperator::Name() const { + return "StringAppendTESTOperator"; +} + + +std::shared_ptr<MergeOperator> +MergeOperators::CreateStringAppendTESTOperator() { + return std::make_shared<StringAppendTESTOperator>(','); +} + +} // namespace ROCKSDB_NAMESPACE |