Add a function which can be used to read the nth
field of a serialized UDT value.
We could deserialize the whole value and then choose
one of the deserialized fields, but that would be wasteful.
Sometimes we only need the value of one field, not all of them.
Signed-off-by: Jan Ciolek <jan.ciolek@scylladb.com>
Add a function which retrieves the value of nth
field from a serialized tuple value.
I tried to make it as efficient as possible.
Other functions, like evaluate(subscript) tend to
deserialize the whole structure and put all of its
elements in a vector. Then they select a single element
from this vector.
This is wasteful, as we only need a single element's value.
This function goes over the serialized fields
and directly returns the one that is needed.
No allocations are needed.
Signed-off-by: Jan Ciolek <jan.ciolek@scylladb.com>
The expression system uses managed_bytes_opt for values, but result_set
uses bytes_opt. This means that processing values from the result set
in expressions requires a copy.
Out of the two, managed_bytes_opt is the better choice, since it prevents
large contiguous allocations for large blobs. So we switch result_set
to use managed_bytes_opt. Users of the result_set API are adjusted.
The db::function interface is not modified to limit churn; instead we
convert the types on entry and exit. This will be adjusted in a following
patch.
compare() and equal() can compare two unfragmented values or two
fragmented values, but a mix of a fragmented value and an unfragmented
value runs afoul of C++ conversion rules. Add more overloads to
make it simpler for users.
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
