The flat_mutation_reader files were conflated and contained multiple
readers, which were not strictly necessary. Splitting optimizes both
iterative compilation times, as touching rarely used readers doesn't
recompile large chunks of codebase. Total compilation times are also
improved, as the size of flat_mutation_reader.hh and
flat_mutation_reader_v2.hh have been reduced and those files are
included by many file in the codebase.
With changes
real 29m14.051s
user 168m39.071s
sys 5m13.443s
Without changes
real 30m36.203s
user 175m43.354s
sys 5m26.376s
Closes#10194
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
Add schema parameter so that:
* Caller has better control over schema -- especially relevant for
reverse reads where it is not possible to follow the convention of
passing the query schema which is reversed compared to that of the
mutations.
* Now that we don't depend on the mutations for the schema, we can lift
the restriction on mutations not being empty: this leads to safer
code. When the mutations parameter is empty, an empty reader is
created.
Add "make_" prefix to follow convention of similar reader factory
functions.
Tests: unit(dev)
Signed-off-by: Botond Dénes <bdenes@scylladb.com>
Message-Id: <20211115155614.363663-1-bdenes@scylladb.com>
There are already four of them. Those working with the mutation reader
can be folded into one with some default args.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
The test intention is not to test how zero estimated partitions
work, there's another case for than (in another test). Also it
looks like 0 is doesn't flow anywhere far, it's std::max-ed into
1 early inside mc::writer constructor.
This changes significantly simplifies the unification of the set
of make_sstable_easy()-s in the next patch.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
There a bunch of places in the test that do the same sequence
of steps to create an sstable. Generalize them into a helper
that resembles the one from previous patch.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
The existing implementation wrongfully shares _all sstables
rather than cloning it. This caused a use-after-free
in `repair_meta::do_estimate_partitions_on_local_shard`
when traversing a shared sstable_set, during which
`table::make_reader_excluding_sstables` erased an entry.
The erase should have happened on a cloned copy
of the sstable_list, not on a shared copy.
The regression was introduced in
c3b8757fa1.
Added a unit test that reproduces the share-on-copy issue
for partitioned_stable_set (sstables::sstable_set).
Fixes#8274
Test: unit(release, debug)
DTest: materialized_views_test.py:TestMaterializedViews.simple_repair_test(debug)
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Reviewed-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20210317145552.701559-1-bhalevy@scylladb.com>
Currently, the sstable_set in a table is copied before every change
to allow accessing the unchanged version by existing sstable readers.
This patch changes the sstable_set to a structure that allows copying
without actually copying all the sstables in the set, while providing
the same methods(and some extra) without majorly decreasing their speed.
This is achieved by associating all copies with sstable_set versions
which hold the changes that were performed in them, and references to
the versions that were copied, a.k.a. their parents. The set represented
by a version is the result of combining all changes of its ancestors.
This causes most methods of the version to have a time complexity
dependent on the number of its ancestors. To limit this number, versions
that represent copies that have already been deleted are merged with its
descendants.
The strategy used for deciding when and with which of its children
should a version be merged heavily depends on the use case of sstable_sets:
there is a main copy of the set in a table class which undergoes many
insertions and deletions, and there are copies of it in compaction or
mutation readers which are further copied or edited few or zero times.
It's worth to mention, that when a copy is made, the copied set should not
be modified anymore, because it would also modify the results given by the
copy. In order to still allow modifying the copied set, if a change is
to be performed on it, the version assiociated with this set is replaced
with a new version depending on the previous one.
As we can see, in our use case there is a main chain of versions(with
changes from the table), and smaller branches of versions that start
from a version from this chain, but are deleted soon after.
In such case we can merge a version when it has exactly one descendant,
as this limits the number of concurrent ancestors of a version to the
number of copies of its ancestors are concurrently used. During each
such merge, the parent version is removed and the child version is
modified so that all operations on it give the same results.
In order to preserve the same interface, the sstable_set still contains a
lw_shared_ptr<sstable_list>, but sstable_list (previously an alias for
unordered_set<shared_sstable>) is now a new structure. Each sstable_set
contains a sstable_list but not every sstable_list has to be contained
by a sstable_set, and we also want to allow fast copying of sstable_lists,
so the reference to the sstable_set_version is kept by the sstable_lists
and the sstable_set can access the sstable_set_version it's associated
with through its sstable_list.
Accessing sstables that are elements of a certain sstable_set copy(so
the select, select_sstable_runs and sstable_list's iterator) get results
from containers that hold all sstables from all versions(which are stored
in a single, shared "versioned_sstable_set_data" structure), and then
filter out these sstables that aren't present in the version in question.
This version of the sstable_set allows adding and erasing the same sstable
repeatedly. Inserting and erasing from the set modifies the containers in
a version only when it has an actual effect: if an sstable has been added
in the parent version, and hasn't been erased in the child version, adding
it again will have no effect. This ensures that when merging versions, the
versions have disjoint sets of added, and erased sstables (an sstable can
still be added in one and erased in the second). It's worth noting hat if
an sstable has been added in one of the merged sets and erased in the
second, the version that remains after merging doesn't need to have any
info about the sstable's inclusion in the set - it can be inferred from
the changes in previous versions (and it doesn't matter if the sstable has
been erased before or after being added).
To release pointers to sstables as soon as possible (i.e. when all references
to versions that contain them die), if an sstable is added/erased in all
child versions that are based on a version which has no external references,
this change gets removed from these versions and added to the parent version.
If an sstable's insertion gets overwritten as a result, we might be able
to remove the sstable completely from the set. We know how many times this
needs to happen by counting, for each sstable, in how many different verisions
has it been added. When a change that adds an sstable gets merged with a change
that removes it, or when a such a change simply gets deleted alongside its
associated version, this count is reduced, and when an sstable gets added to a
version that doesn't already contain it, this count is increased.
The methods that modify the sets contents give strong exception guarantee
by trying to insert new sstables to its containers, and erasing them in
the case of an caught exception.
Fixes#2622
Signed-off-by: Wojciech Mitros <wojciech.mitros@scylladb.com>
