f5b05cf981
in C++20, compiler generate operator!=() if the corresponding operator==() is already defined, the language now understands that the comparison is symmetric in the new standard. fortunately, our operator!=() is always equivalent to `! operator==()`, this matches the behavior of the default generated operator!=(). so, in this change, all `operator!=` are removed. in addition to the defaulted operator!=, C++20 also brings to us the defaulted operator==() -- it is able to generated the operator==() if the member-wise lexicographical comparison. under some circumstances, this is exactly what we need. so, in this change, if the operator==() is also implemented as a lexicographical comparison of all memeber variables of the class/struct in question, it is implemented using the default generated one by removing its body and mark the function as `default`. moreover, if the class happen to have other comparison operators which are implemented using lexicographical comparison, the default generated `operator<=>` is used in place of the defaulted `operator==`. sometimes, we fail to mark the operator== with the `const` specifier, in this change, to fulfil the need of C++ standard, and to be more correct, the `const` specifier is added. also, to generate the defaulted operator==, the operand should be `const class_name&`, but it is not always the case, in the class of `version`, we use `version` as the parameter type, to fulfill the need of the C++ standard, the parameter type is changed to `const version&` instead. this does not change the semantic of the comparison operator. and is a more idiomatic way to pass non-trivial struct as function parameters. please note, because in C++20, both operator= and operator<=> are symmetric, some of the operators in `multiprecision` are removed. they are the symmetric form of the another variant. if they were not removed, compiler would, for instance, find ambiguous overloaded operator '=='. this change is a cleanup to modernize the code base with C++20 features. Signed-off-by: Kefu Chai <kefu.chai@scylladb.com> Closes #13687
132 lines
3.8 KiB
C++
132 lines
3.8 KiB
C++
/*
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* Copyright (C) 2015-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: AGPL-3.0-or-later
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*/
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#pragma once
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#include <seastar/core/shared_ptr.hh>
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#include "types/types.hh"
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#include "schema/schema.hh"
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#include <optional>
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#include <stdexcept>
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class mutation;
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namespace query {
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class result;
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class no_value : public std::runtime_error {
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public:
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using runtime_error::runtime_error;
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};
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class non_null_data_value {
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data_value _v;
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public:
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explicit non_null_data_value(data_value&& v);
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operator const data_value&() const {
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return _v;
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}
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};
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inline bool operator==(const non_null_data_value& x, const non_null_data_value& y) {
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return static_cast<const data_value&>(x) == static_cast<const data_value&>(y);
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}
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// Result set row is a set of cells that are associated with a row
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// including regular column cells, partition keys, as well as static values.
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class result_set_row {
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schema_ptr _schema;
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const std::unordered_map<sstring, non_null_data_value> _cells;
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public:
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result_set_row(schema_ptr schema, std::unordered_map<sstring, non_null_data_value>&& cells)
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: _schema{schema}
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, _cells{std::move(cells)}
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{ }
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// Look up a deserialized row cell value by column name
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const data_value*
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get_data_value(const sstring& column_name) const {
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auto it = _cells.find(column_name);
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if (it == _cells.end()) {
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return nullptr;
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}
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return &static_cast<const data_value&>(it->second);
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}
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// Look up a deserialized row cell value by column name
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template<typename T>
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std::optional<T>
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get(const sstring& column_name) const {
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if (const auto *value = get_ptr<T>(column_name)) {
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return std::optional(*value);
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}
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return std::nullopt;
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}
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template<typename T>
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const T*
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get_ptr(const sstring& column_name) const {
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const auto *value = get_data_value(column_name);
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if (value == nullptr) {
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return nullptr;
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}
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return &value_cast<T>(*value);
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}
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// throws no_value on error
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template<typename T>
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const T& get_nonnull(const sstring& column_name) const {
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auto v = get_ptr<std::remove_reference_t<T>>(column_name);
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if (v) {
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return *v;
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}
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throw no_value(column_name);
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}
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const std::unordered_map<sstring, non_null_data_value>& cells() const { return _cells; }
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friend inline bool operator==(const result_set_row& x, const result_set_row& y) = default;
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friend std::ostream& operator<<(std::ostream& out, const result_set_row& row);
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};
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// Result set is an in-memory representation of query results in
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// deserialized format. To obtain a result set, use the result_set_builder
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// class as a visitor to query_result::consume() function.
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class result_set {
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schema_ptr _schema;
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std::vector<result_set_row> _rows;
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public:
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static result_set from_raw_result(schema_ptr, const partition_slice&, const result&);
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result_set(schema_ptr s, std::vector<result_set_row>&& rows)
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: _schema(std::move(s)), _rows{std::move(rows)}
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{ }
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explicit result_set(const mutation&);
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bool empty() const {
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return _rows.empty();
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}
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// throws std::out_of_range on error
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const result_set_row& row(size_t idx) const {
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if (idx >= _rows.size()) {
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throw std::out_of_range("no such row in result set: " + std::to_string(idx));
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}
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return _rows[idx];
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}
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const std::vector<result_set_row>& rows() const {
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return _rows;
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}
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const schema_ptr& schema() const {
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return _schema;
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}
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friend inline bool operator==(const result_set& x, const result_set& y);
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friend std::ostream& operator<<(std::ostream& out, const result_set& rs);
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};
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inline bool operator==(const result_set& x, const result_set& y) {
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return x._rows == y._rows;
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}
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}
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