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
Move replica-oriented classes to the replica namespace. The main
classes moved are ::database, ::keyspace, and ::table, but a few
ancillary classes are also moved. There are certainly classes that
should be moved but aren't (like distributed_loader) but we have
to start somewhere.
References are adjusted treewide. In many cases, it is obvious that
a call site should not access the replica (but the data_dictionary
instead), but that is left for separate work.
scylla-gdb.py is adjusted to look for both the new and old names.
Incremental selection may not work properly for LCS and ICS due to an
use-after-free bug in partitioned set which came into existence after
compound set was introduced.
The use-after-free happens because partitioned set wasn't taking into
account that the next position can become the current position in the
next iteration, which will be used by all selectors managed by
compound set. So if next position is freed, when it were being used
as current position, subsequent selectors would find the current
position freed, making them produce incorrect results.
Fix this by moving ownership of next pos from incremental_selector_impl
to incremental_selector, which makes it more robust as the latter knows
better when the selection is done with the next pos. incremental_selector
will still return ring_position_view to avoid copies.
Fixes#8802.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20210611130957.156712-1-raphaelsc@scylladb.com>
Compound set's incremental selector isn't needed when only one set
contains sstables, which is the common case because secondary set
will only contain data during maintenance operations.
From now on, if only primary set contains data, its selector will
be built directly without compound set's selector acting as an
interposer.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20210607193651.126937-1-raphaelsc@scylladb.com>
This function will be reused by TWCS reshape when checking if all
sstables in a window are disjoint and can be all compacted together.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
This new sstable set implementation is useful for combining operation of
multiple sstable sets, which can still be referenced individually via
its shared ptr reference.
It will be used when maintenance set is introduced in table, so a
compound set is required to allow both sets to have their operations
efficiently combined.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
after compound set is introduced, select_sstable_runs() will no longer
work because the sstable runs live in sstable_set, but they should
actually live in the sstable_set being written to.
Given that runs is a concept that belongs only to strategies which
use partitioned_sstable_set, let's move the implementation of
select_sstable_runs() to it.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20210312042255.111060-2-raphaelsc@scylladb.com>
This new method is preferred over all() for iterations purposes, because
all() may have to copy sstables into a temporary.
For example, all() implementation of the upcoming compound_sstable_set
will have no choice but to merge all sstables from N managed sets into
a temporary.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20210311163009.42210-1-raphaelsc@scylladb.com>
The main motivation behind this is that by moving all() impl into
sstable_set_impl, sstable_set no longer needs to maintain a list
with all sstables, which in turn may disagree with the respective
sstable_set_impl.
This will be very important for compound_sstable_set_impl which
will be built from existing sets, and will implement all() by
combining the all() of its managed sets.
Without this patch, we'd have to insert the same sstable at
both compound set and also the set managed by it, to guarantee
all() of compound set would return the correct data, which would
be expensive and error prone.
Signed-off-by: Raphael S. Carvalho <raphaelsc@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>
Adding an non-empty set of sstables as the set of all sstables in
an sstable_set could cause inconsistencies with the values returned
by select_sstable_runs because the _all_runs map would still be
initialized empty. For similar reasons, the provided sstable_set_impl
should also be empty.
Dispel doubts by removing the unordered_set from the constructor, and
adding a check of emptiness of the sstable_set_impl.
Signed-off-by: Wojciech Mitros <wojciech.mitros@scylladb.com>
We want to unify the various sstable reader creation methods and this
method taking a ring position instead of a partition range like
everybody else stands in the way of that.
This is effect reverts 68663d0de.
This reverts commit dc77d128e9. It was reverted
due to a strange and unexplained diff, which is now explained. The
HEAD on the working directory being pulled from was set back, so git
thought it was merging the intended commits, plus all the work that was
committed from HEAD to master. So it is safe to restore it.
This reverts commit 0aa1f7c70a, reversing
changes made to 72c59e8000. The diff is
strange, including unrelated commits. There is no understanding of the
cause, so to be safe, revert and try again.
instead of partition_range.
It would be best to pass `partition_key` or `decorated_key` here.
However, the implementation of this function needs a `partition_range`
to pass into `sstable_set::select`, and `partition_range` must be
constructed from `ring_position`s. We could create the `ring_position`
internally from the key but that would involve a copy which we want to
avoid.
Lower level functions such as `create_single_key_sstable_reader`
were made methods of `sstable_set`.
The motivation is that each concrete sstable_set
may decide to use a better sstable reading algorithm specific to the
data structures used by this sstable_set. For this it needs to access
the set's internals.
A nice side effect is that we moved some code out of table.cc
and database.hh which are huge files.
select() is too generic for the method that retrieve sstable runs,
and it has a completely different meaning that the former select
method used to select sstables based on token range.
let's give it a more descriptive name.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20200811193401.22749-1-raphaelsc@scylladb.com>
Instead of an `std::unique_ptr<sstable_set_impl>`. The latter doesn't
have a publicly available destructor, so it can only be called from
withing `sstables/compaction_strategy.cc` where its definition resides.
Thus it is not really usable as a public function in its current form,
which shows as it has no users either.
This patch makes it usable by returning an `sstable_set`. That is what
potential callers would want anyway. In fact this patch prepares the
ground for the next one, which wishes to use this function for just
that but can't in its current form.
To make it available, we'll need to make it optional the usage of level metadata,
used to deal with interval map's fragmentation issue when level 0 falls behind,
and also introduce a interface for compaction strategies to implement
make_sstable_set() that instantiate partitioned sstable set.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20190424232948.668-1-raphaelsc@scylladb.com>
sstable run is a structure that will hold all sstables that has the same
run identifier. All sstables belonging to the same run will not overlap
with one another.
It can be used by compaction strategy to work on runs instead of individual
sstables.
sstable_set structure which holds all sstables for a given column family
will be responsible for providing to its user an interface to work with
runs instead of individual sstables.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
The motivation is that compaction may remove a sstable from the set while the
incremental selector is alive, and for that to work, we need to invalidate
the iterators stored by the selector. We could have added a method to notify
it, but there will be a case where the one keeping the set cannot forward
the notification to the selector. So it's better for the selector to take
care of itself. Change counter approach is used which allows the selector
to know when to invalidate the iterators.
After invalidation, selector will move the iterator back into its right
place by looking for lower bound for current pos.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Currently `sstable_set::incremental_selector` works in terms of tokens.
Sstables can be selected with tokens and internally the token-space is
partitioned (in `partitioned_sstable_set`, used for LCS) with tokens as
well. This is problematic for severeal reasons.
The sub-range sstables cover from the token-space is defined in terms of
decorated keys. It is even possible that multiple sstables cover
multiple non-overlapping sub-ranges of a single token. The current
system is unable to model this and will at best result in selecting
unnecessary sstables.
The usage of token for providing the next position where the
intersecting sstables change [1] causes further problems. Attempting to
walk over the token-space by repeatedly calling `select()` with the
`next_position` returned from the previous call will quite possibly lead
to an infinite loop as a token cannot express inclusiveness/exclusiveness
and thus the incremental selector will not be able to make progress when
the upper and lower bounds of two neighbouring intervals share the same
token with different inclusiveness e.g. [t1, t2](t2, t3].
To solve these problems update incremental_selector to work in terms of
ring position. This makes it possible to partition the token-space
amoing sstables at decorated key granularity. It also makes it possible
for select() to return a next_position that is guaranteed to make
progress.
partitioned_sstable_set now builds the internal interval map using the
decorated key of the sstables, not just the tokens.
incremental_selector::select() now uses `dht::ring_position_view` as
both the selector and the next_position. ring_position_view can express
positions between keys so it can also include information about
inclusiveness/exclusiveness of the next interval guaranteeing forward
progress.
[1] `sstable_set::incremental_selector::selection::next_position`
The issue is triggered by compaction of sstables of level higher than 0.
The problem happens when interval map of partitioned sstable set stores
intervals such as follow:
[-9223362900961284625 : -3695961740249769322 ]
(-3695961740249769322 : -3695961103022958562 ]
When selector is called for first interval above, the exclusive lower
bound of the second interval is returned as next token, but the
inclusivess info is not returned.
So reader_selector was returning that there *were* new readers when
the current token was -3695961740249769322 because it was stored in
selector position field as inclusive, but it's actually exclusive.
This false positive was leading to infinite recursion in combined
reader because sstable set's incremental selector itself knew that
there were actually *no* new readers, and therefore *no* progress
could be made.
Fix is to use ring_position in reader_selector, such that
inclusiveness would be respected.
So reader_selector::has_new_readers() won't return false positive
under the conditions described above.
Fixes#2908.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
A seletion contains - in addition to the list of sstables - a next_token
which is a hint as to what is the next best token to call select() with.
This should be the smallest token such that at the next call to
select() the least number of new sstables will be returned, without
skipping any.
Incrementally select sstables from sstable set using token
in ascending order.
For leveled strategy, it returns all sstables that belong
to current interval. For other strategies, it just return
all sstables from the set.
Useful for compaction which needs all sstables that overlap
with key being currently compacted to calculate maximum
purgeable timestamp.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
sstable_set abstracts the notion of a container of sstables, allowing
different compaction strategies to supply their own implementation. The
intended user is leveled compaction strategy; since it partitions sstables,
it can quickly restrict the number of sstables that participate in a query
by looking at the min/max partition key.
sstable_set also maintains an internal lw_shared_ptr<sstable_list>,
in parallel with the abstract container. This is to support
column_family::get_sstable(), which returns a lw_shared_ptr<sstable_list>
which must be anchored somewhere if it is not saved at the caller side,
as it isn't in most current callers.
