Files
scylladb/mutation_query.hh
Kefu Chai f5b05cf981 treewide: use defaulted operator!=() and operator==()
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
2023-04-27 10:24:46 +03:00

181 lines
6.0 KiB
C++

/*
* Copyright (C) 2015-present ScyllaDB
*/
/*
* SPDX-License-Identifier: AGPL-3.0-or-later
*/
#pragma once
#include "query-request.hh"
#include "query-result.hh"
#include "mutation/frozen_mutation.hh"
#include "db/timeout_clock.hh"
#include "mutation/mutation.hh"
#include "utils/chunked_vector.hh"
#include "mutation/range_tombstone_assembler.hh"
class reconcilable_result;
class frozen_reconcilable_result;
class mutation_source;
// Can be read by other cores after publishing.
struct partition {
uint32_t _row_count_low_bits;
frozen_mutation _m; // FIXME: We don't need cf UUID, which frozen_mutation includes.
uint32_t _row_count_high_bits;
partition(uint32_t row_count_low_bits, frozen_mutation m, uint32_t row_count_high_bits)
: _row_count_low_bits(row_count_low_bits)
, _m(std::move(m))
, _row_count_high_bits(row_count_high_bits)
{ }
partition(uint64_t row_count, frozen_mutation m)
: _row_count_low_bits(static_cast<uint32_t>(row_count))
, _m(std::move(m))
, _row_count_high_bits(static_cast<uint32_t>(row_count >> 32))
{ }
uint32_t row_count_low_bits() const {
return _row_count_low_bits;
}
uint32_t row_count_high_bits() const {
return _row_count_high_bits;
}
uint64_t row_count() const {
return (static_cast<uint64_t>(_row_count_high_bits) << 32) | _row_count_low_bits;
}
const frozen_mutation& mut() const {
return _m;
}
frozen_mutation& mut() {
return _m;
}
bool operator==(const partition& other) const {
return row_count() == other.row_count() && _m.representation() == other._m.representation();
}
};
// The partitions held by this object are ordered according to dht::decorated_key ordering and non-overlapping.
// Each mutation must have different key.
//
// Can be read by other cores after publishing.
class reconcilable_result {
uint32_t _row_count_low_bits;
query::short_read _short_read;
query::result_memory_tracker _memory_tracker;
utils::chunked_vector<partition> _partitions;
uint32_t _row_count_high_bits;
public:
~reconcilable_result();
reconcilable_result();
reconcilable_result(reconcilable_result&&) = default;
reconcilable_result& operator=(reconcilable_result&&) = default;
reconcilable_result(uint32_t row_count_low_bits, utils::chunked_vector<partition> partitions, query::short_read short_read,
uint32_t row_count_high_bits, query::result_memory_tracker memory_tracker = { });
reconcilable_result(uint64_t row_count, utils::chunked_vector<partition> partitions, query::short_read short_read,
query::result_memory_tracker memory_tracker = { });
const utils::chunked_vector<partition>& partitions() const;
utils::chunked_vector<partition>& partitions();
uint32_t row_count_low_bits() const {
return _row_count_low_bits;
}
uint32_t row_count_high_bits() const {
return _row_count_high_bits;
}
uint64_t row_count() const {
return (static_cast<uint64_t>(_row_count_high_bits) << 32) | _row_count_low_bits;
}
query::short_read is_short_read() const {
return _short_read;
}
size_t memory_usage() const {
return _memory_tracker.used_memory();
}
bool operator==(const reconcilable_result& other) const;
struct printer {
const reconcilable_result& self;
schema_ptr schema;
friend std::ostream& operator<<(std::ostream&, const printer&);
};
printer pretty_printer(schema_ptr) const;
};
class reconcilable_result_builder {
const schema& _schema;
const query::partition_slice& _slice;
bool _reversed;
bool _return_static_content_on_partition_with_no_rows{};
bool _static_row_is_alive{};
uint64_t _total_live_rows = 0;
query::result_memory_accounter _memory_accounter;
stop_iteration _stop;
std::optional<streamed_mutation_freezer> _mutation_consumer;
range_tombstone_assembler _rt_assembler;
uint64_t _live_rows{};
// make this the last member so it is destroyed first. #7240
utils::chunked_vector<partition> _result;
private:
stop_iteration consume(range_tombstone&& rt);
public:
// Expects table schema (non-reversed) and half-reversed (legacy) slice when building results for reverse query.
reconcilable_result_builder(const schema& s, const query::partition_slice& slice,
query::result_memory_accounter&& accounter) noexcept
: _schema(s), _slice(slice), _reversed(_slice.options.contains(query::partition_slice::option::reversed))
, _memory_accounter(std::move(accounter))
{ }
void consume_new_partition(const dht::decorated_key& dk);
void consume(tombstone t);
stop_iteration consume(static_row&& sr, tombstone, bool is_alive);
stop_iteration consume(clustering_row&& cr, row_tombstone, bool is_alive);
stop_iteration consume(range_tombstone_change&& rtc);
stop_iteration consume_end_of_partition();
reconcilable_result consume_end_of_stream();
};
future<query::result> to_data_query_result(
const reconcilable_result&,
schema_ptr,
const query::partition_slice&,
uint64_t row_limit,
uint32_t partition_limit,
query::result_options opts = query::result_options::only_result());
// Query the content of the mutation.
//
// The mutation is destroyed in the process, see `mutation::consume()`.
query::result query_mutation(
mutation&& m,
const query::partition_slice& slice,
uint64_t row_limit = query::max_rows,
gc_clock::time_point now = gc_clock::now(),
query::result_options opts = query::result_options::only_result());
// Performs a query for counter updates.
future<mutation_opt> counter_write_query(schema_ptr, const mutation_source&, reader_permit permit,
const dht::decorated_key& dk,
const query::partition_slice& slice,
tracing::trace_state_ptr trace_ptr);