This method can cause performance regressions if used in the wrong place
-- namely if it is used to abort reads by throwing the abort exception.
Exceptions should be propagated during reads without throwing them,
otherwise they cause extra CPU load, making a bad situation worse.
Remove this method, so it doesn't accidentally get more users, migrate
remaining users to get_abort_exception().
Will replace check_abort(). The latter throws an exception which is
something we want to avoid when a read is aborted, in particular when it
times out.
Also add a convenience get_abort_exception() method to mutation_reader.
C++20 introduced two new attributes--likely and unlikely--that
function as a built-in replacement for __builtin_expect implemented
in various compilers. Since it makes code easier to read and it's
an integral part of the language, there's no reason to not use it
instead.
Closesscylladb/scylladb#24786
these unused includes were identified by clang-include-cleaner. after
auditing these source files, all of the reports have been confirmed.
in which, instead of using `seastarx.hh`, `readers/mutation_reader.hh`,
use `using seastar::future` to include `future` in the global namespace,
this makes `readers/mutation_reader.hh` a header exposing `future<>`,
but this is not a good practice, because, unlike `seastarx.hh` or
`seastar/core/future.hh`, `reader/mutation_reader.hh` is not
responsible for exposing seastar declarations. so, we trade the
using statement for `#include "seastarx.hh"` in that file to decouple
the source files including it from this header because of this statement.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#22439
The `consume*()` variants just forward the call to the `_impl` method
with the same name. The latter, being a member of `::impl`, will bypass
the top level `fill_buffer()`, etc. methods and thus will never call
`set_close_required()`. Do this in the top-level `consume*()` methods
instead, to ensure a reader, on which only `consume*()` is called, and
then is destroyed, will complain as it should (and abort).
operator()() was also missing `set_close_required()`, fix that too.
flat_mutation_reader_v2 was introduced in a pair of commits in 2021:
e3309322c3 "Clone flat_mutation_reader related classes into v2 variants"
08b5773c12 "Adapt flat_mutation_reader_v2 to the new version of the API"
as a replacement for flat_mutation_reader, using range_tombstone_change
instead of range_tombstone to represent represent range tombstones. See
those commits for more information.
The transition was incremental; the last use of the original
flat_mutation_reader was removed in 2022 in commit
026f8cc1e7 "db: Use mutation_partition_v2 in mvcc"
In turn, flat_mutation_reader was introduced in 2017 in commit
748205ca75 "Introduce flat_mutation_reader"
To transition from a mutation_reader that nested rows within
a partition in a separate stream, to a flat reader that streamed
partitions and rows in the same stream.
Here, we reclaim the original name and rename the awkward
flat_mutation_reader_v2 to mutation_reader.
Note that mutation_fragment_v2 remains since we still use the original
for compatibilty, sometimes.
Some notes about the transition:
- files were also renamed. In one case (flat_mutation_reader_test.cc), the
rename target already existed, so we rename to
mutation_reader_another_test.cc.
- a namespace 'mutation_reader' with two definitions existed (in
mutation_reader_fwd.hh). Its contents was folded into the mutation_reader
class. As a result, a few #includes had to be adjusted.
Closesscylladb/scylladb#19356
