Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
The database, keyspace, and table classes represent the replica-only
part of the objects after which they are named. Reading from a table
doesn't give you the full data, just the replica's view, and it is not
consistent since reconciliation is applied on the coordinator.
As a first step in acknowledging this, move the related files to
a replica/ subdirectory.
Seastar recently lost support for the experimental Concepts Technical
Specification (TS) and gained support for C++20 concepts. Re-enable
concepts in Scylla by updating our use of concepts to the C++20
standard.
This change:
- peels off uses of the GCC6_CONCEPT macro
- removes inclusions of <seastar/gcc6-concepts.hh>
- replaces function-style concepts (no longer supported) with
equation-style concepts
- semicolons added and removed as needed
- deprecated std::is_pod replaced by recommended replacement
- updates return type constraints to use concepts instead of
type names (either std::same_as or std::convertible_to, with
std::same_as chosen when possible)
No attempt is made to improve the concepts; this is a specification
update only.
Message-Id: <20200531110254.2555854-1-avi@scylladb.com>
mutation_partition_view now supports a compile-time resolved visitor.
This is performant but results in bloat when the performance is not
needed. Furthermore, the template function that applies the object
to the visitor is private and out-of-line, to reduce compile time.
To allow visitation on mutation_partition_view objects, add a virtual
visitor type and a non-template accept function.
Note: mutation_partition_visitor is very similar to the new type,
but different enough to break the template visitor which is used
to implement the new visitor.
The new visitor will be used to implement pretty printing for
canonical_mutation.
mutation_partition_view needs to create an atomic_cell from
IDL-serialised data. Then that cell is passed to the visitor. However,
because generic mutation_partition_visitor interface was used, the cell
was passed by constant reference which forced the visitor to needlessly
copy it.
This patch takes advantage of the fact that mutation_partition_view is
devirtualised now and adjust the interfaces of its visitors so that the
cell can be passed without copying.
There are only two types of visitors used and only one of them appears
in the hot path. They can be devirtualised without too much effort,
which also enables future custom interface specialisations specific to
mutation_partition_views and its users, not necessairly in the scope of
more general mutation_partition_visitor.
Some users (e.g. reconciliation code) need only to know the clustering
key of the first or the last row in the partition. This was done with a
full visitor visiting every single cell of the partition, which is very
wasteful. This patch adds direct getters for the needed information.
The immediate motivation for introducing frozen_mutation is inability
to deserialize current "mutation" object, which needs schema reference
at the time it's constructed. It needs schema to initialize its
internal maps with proper key comparators, which depend on schema.
frozen_mutation is an immutable, compact form of a mutation. It
doesn't use complex in-memory strucutres, data is stored in a linear
buffer. In case of frozen_mutation schema needs to be supplied only at
the time mutation partition is visited. Therefore it can be trivially
deserialized without schema.
