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clustering_bounds_comparator.hh
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clustering_bounds_comparator.hh
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/*
* Copyright (C) 2016-present ScyllaDB
*/
/*
* SPDX-License-Identifier: AGPL-3.0-or-later
*/
#pragma once
#include <functional>
#include "keys.hh"
#include "schema_fwd.hh"
#include "range.hh"
/**
* Represents the kind of bound in a range tombstone.
*/
enum class bound_kind : uint8_t {
excl_end = 0,
incl_start = 1,
// values 2 to 5 are reserved for forward Origin compatibility
incl_end = 6,
excl_start = 7,
};
std::ostream& operator<<(std::ostream& out, const bound_kind k);
// Swaps start <-> end && incl <-> excl
bound_kind invert_kind(bound_kind k);
// Swaps start <-> end
bound_kind reverse_kind(bound_kind k);
int32_t weight(bound_kind k);
class bound_view {
const static thread_local clustering_key _empty_prefix;
std::reference_wrapper<const clustering_key_prefix> _prefix;
bound_kind _kind;
public:
bound_view(const clustering_key_prefix& prefix, bound_kind kind)
: _prefix(prefix)
, _kind(kind)
{ }
bound_view(const bound_view& other) noexcept = default;
bound_view& operator=(const bound_view& other) noexcept = default;
bound_kind kind() const { return _kind; }
const clustering_key_prefix& prefix() const { return _prefix; }
struct tri_compare {
// To make it assignable and to avoid taking a schema_ptr, we
// wrap the schema reference.
std::reference_wrapper<const schema> _s;
tri_compare(const schema& s) : _s(s)
{ }
std::strong_ordering operator()(const clustering_key_prefix& p1, int32_t w1, const clustering_key_prefix& p2, int32_t w2) const {
auto type = _s.get().clustering_key_prefix_type();
auto res = prefix_equality_tri_compare(type->types().begin(),
type->begin(p1.representation()), type->end(p1.representation()),
type->begin(p2.representation()), type->end(p2.representation()),
::tri_compare);
if (res != 0) {
return res;
}
auto d1 = p1.size(_s);
auto d2 = p2.size(_s);
/*
* The logic below is
*
* if d1 == d2 { return w1 <=> w2 }
* if d1 < d2 { if w1 <= 0 return less else return greater
* if d1 > d2 { if w2 <= 0 return greater else return less
*
* Those w vs 0 checks are effectively { w <=> 0.5 } which is the same
* as { 2*w <=> 1 }. Next, w1 <=> w2 is equivalent to 2*w1 <=> 2*w2, so
* all three branches can be collapsed into a single <=>.
*
* This looks like veiling the above ifs for no reason, but it really
* helps compiler generate jump-less assembly.
*/
return ((d1 <= d2) ? w1 << 1 : 1) <=> ((d2 <= d1) ? w2 << 1 : 1);
}
std::strong_ordering operator()(const bound_view b, const clustering_key_prefix& p) const {
return operator()(b._prefix, weight(b._kind), p, 0);
}
std::strong_ordering operator()(const clustering_key_prefix& p, const bound_view b) const {
return operator()(p, 0, b._prefix, weight(b._kind));
}
std::strong_ordering operator()(const bound_view b1, const bound_view b2) const {
return operator()(b1._prefix, weight(b1._kind), b2._prefix, weight(b2._kind));
}
};
struct compare {
// To make it assignable and to avoid taking a schema_ptr, we
// wrap the schema reference.
tri_compare _cmp;
compare(const schema& s) : _cmp(s)
{ }
bool operator()(const clustering_key_prefix& p1, int32_t w1, const clustering_key_prefix& p2, int32_t w2) const {
return _cmp(p1, w1, p2, w2) < 0;
}
bool operator()(const bound_view b, const clustering_key_prefix& p) const {
return operator()(b._prefix, weight(b._kind), p, 0);
}
bool operator()(const clustering_key_prefix& p, const bound_view b) const {
return operator()(p, 0, b._prefix, weight(b._kind));
}
bool operator()(const bound_view b1, const bound_view b2) const {
return operator()(b1._prefix, weight(b1._kind), b2._prefix, weight(b2._kind));
}
};
bool equal(const schema& s, const bound_view other) const {
return _kind == other._kind && _prefix.get().equal(s, other._prefix.get());
}
bool adjacent(const schema& s, const bound_view other) const {
return invert_kind(other._kind) == _kind && _prefix.get().equal(s, other._prefix.get());
}
static bound_view bottom() {
return {_empty_prefix, bound_kind::incl_start};
}
static bound_view top() {
return {_empty_prefix, bound_kind::incl_end};
}
template<template<typename> typename R>
requires Range<R, clustering_key_prefix_view>
static bound_view from_range_start(const R<clustering_key_prefix>& range) {
return range.start()
? bound_view(range.start()->value(), range.start()->is_inclusive() ? bound_kind::incl_start : bound_kind::excl_start)
: bottom();
}
template<template<typename> typename R>
requires Range<R, clustering_key_prefix>
static bound_view from_range_end(const R<clustering_key_prefix>& range) {
return range.end()
? bound_view(range.end()->value(), range.end()->is_inclusive() ? bound_kind::incl_end : bound_kind::excl_end)
: top();
}
template<template<typename> typename R>
requires Range<R, clustering_key_prefix>
static std::pair<bound_view, bound_view> from_range(const R<clustering_key_prefix>& range) {
return {from_range_start(range), from_range_end(range)};
}
template<template<typename> typename R>
requires Range<R, clustering_key_prefix_view>
static std::optional<typename R<clustering_key_prefix_view>::bound> to_range_bound(const bound_view& bv) {
if (&bv._prefix.get() == &_empty_prefix) {
return {};
}
bool inclusive = bv._kind != bound_kind::excl_end && bv._kind != bound_kind::excl_start;
return {typename R<clustering_key_prefix_view>::bound(bv._prefix.get().view(), inclusive)};
}
friend std::ostream& operator<<(std::ostream& out, const bound_view& b) {
return out << "{bound: prefix=" << b._prefix.get() << ", kind=" << b._kind << "}";
}
};