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
<iterator> was introduced back in
1cf02cb9d8, but lexicographical_compare.hh
was extracted out in bdfc0aa748, since we
don't have any users of <iterator> in types.hh anymore, let's remove it.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#13327
UUID_test uses lexicograhical_compare from the types module. This
is a layering violation, since UUIDs are at a much lower level than
the database type system. In practical terms, this cause link failures
with gcc due to some thread-local-storage variables defined in types.hh
but not provided by any object, since we don't link with types.o in this
test.
Fix by extracting the relevant functions into a new header.
The code for compare_endpoints originates at the dawn of time (bc034aeaec)
and is called on the fast path from storage_proxy via `sort_by_proximity`.
This series considerably reduces the function's footprint by:
1. carefully coding the many comparisons in the function so to reduce the number of conditional banches (apparently the compiler isn't doing a good enough job at optimizing it in this case)
2. avoid sstring copy in topology::get_{datacenter,rack}
Closes#12761
* github.com:scylladb/scylladb:
topology: optimize compare_endpoints
to_string: add print operators for std::{weak,partial}_ordering
utils: to_sstring: deinline std::strong_ordering print operator
move to_string.hh to utils/
test: network_topology: add test_topology_compare_endpoints
data_type_for() is a function template that converts a C++
type to a database dynamic type (data_type object).
Instead of implementing a function per type, implement a variable
template instance. This is shorter and nicer.
Since the original type variables (e.g. long_type) are defined separately,
use a reference instead of copying to avoid initialization order problems.
To catch misuses of data_type_for the general data_type_for_v variable
template maps to some unused tag type which will cause a build error
when instantiated.
The original motivation for this was to allow for partial
specialization of data_type_for() for tuple types, but this isn't
really workable since the native type for tuples is std::vector<data_value>,
not std::tuple, and I only checked this after getting the work done,
so this isn't helping anything; it's just a little nicer.
Closes#13043
they are part of the CQL type system, and are "closer" to types.
let's move them into "types" directory.
the building systems are updated accordingly.
the source files referencing `types.hh` were updated using following
command:
```
find . -name "*.{cc,hh}" -exec sed -i 's/\"types.hh\"/\"types\/types.hh\"/' {} +
```
the source files under sstables include "types.hh", which is
indeed the one located under "sstables", so include "sstables/types.hh"
instea, so it's more explicit.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#12926
