When next_partition() or fast_forward_to() is called. Instead of trying
to simulate a properly closed partition by injecting synthetic mutation
fragments to properly close it.
The fragment reader currently unconditionally forwards its buffer to the
passed-in partition range. Even if this range is
`query::full_partition_range`, this will involve dropping any fragments
up to the first partitions tart. This causes problems for test users who
intentionally create invalid fragment streams, that don't start with a
partition-start.
Refactor the reader to not do any modifications on the stream, when
neither slice, nor partition-range was passed by the user.
When wiring multi range reader with cleanup, I found that cleanup
wouldn't be able to release disk space of input SSTables earlier.
The reason is that multi range reader fast forward to the next range,
therefore it enables mutation_reader::forwarding, and as a result,
combined reader cannot release readers proactively as it cannot tell
for sure that the underlying reader is exhausted. It may have reached
EOS for the current range, but it may have data for the next one.
The concept of EOS actually only applies to the current range being
read. A reader that returned EOS will actually get out of this
state once the combined reader fast forward to the next range.
Therefore, only the underlying reader, i.e. the sstable reader,
can for certain know that the data source is completely exhausted,
given that tokens are read in monotonically increasing order.
For reversed reads, that's not true but fast forward to range
is not actually supported yet for it.
Today, the SSTable reader already knows that the underlying SSTable
was exhausted in fast_forward_to(), after it call index_reader's
advance_to(partition_range), therefore it disables subsequent
reads. We can take a step further and also check that the index
was exhausted, i.e. reached EOF.
So if the index is exhausted, and there's no partition to read
after the fast_forward_to() call, we know that there's nothing
left to do in this reader, and therefore the reader can be
closed proactively, allowing the disk space of SSTable to be
reclaimed if it was already deleted.
We can see that the combined reader, under multi range reader,
will incrementally find a set of disjoint SSTable exhausted,
as it fast foward to owned ranges
1:
INFO 2023-07-05 10:51:09,570 [shard 0] mutation_reader - flat_multi_range_mutation_reader(): fast forwarding to range [{-4525396453480898112, start},{-4525396453480898112, end}]
INFO 2023-07-05 10:51:09,570 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-1-big-Data.db, start == *end, eof ? true
INFO 2023-07-05 10:51:09,570 [shard 0] sstable - closing reader 0x60100029d800 for /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-1-big-Data.db
INFO 2023-07-05 10:51:09,570 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-3-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,570 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-4-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,570 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-5-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,570 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-6-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,570 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-7-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,570 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-8-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,570 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-9-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,570 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-10-big-Data.db, start == *end, eof ? false
2:
INFO 2023-07-05 10:51:09,572 [shard 0] mutation_reader - flat_multi_range_mutation_reader(): fast forwarding to range [{-2253424581619911583, start},{-2253424581619911583, end}]
INFO 2023-07-05 10:51:09,572 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-2-big-Data.db, start == *end, eof ? true
INFO 2023-07-05 10:51:09,572 [shard 0] sstable - closing reader 0x60100029d400 for /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-2-big-Data.db
INFO 2023-07-05 10:51:09,572 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-4-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,572 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-5-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,572 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-6-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,572 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-7-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,572 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-8-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,572 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-9-big-Data.db, start == *end, eof ? false
INFO 2023-07-05 10:51:09,572 [shard 0] sstable - sstable /tmp/scylla-9831a31a-66f3-4541-8681-000ac8e21bbb/me-10-big-Data.db, start == *end, eof ? false
And so on.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
In that level no io_priority_class-es exist. Instead, all the IO happens
in the context of current sched-group. File API no longer accepts prio
class argument (and makes io_intent arg mandatory to impls).
So the change consists of
- removing all usage of io_priority_class
- patching file_impl's inheritants to updated API
- priority manager goes away altogether
- IO bandwidth update is performed on respective sched group
- tune-up scylla-gdb.py io_queues command
The first change is huge and was made semi-autimatically by:
- grep io_priority_class | default_priority_class
- remove all calls, found methods' args and class' fields
Patching file_impl-s is smaller, but also mechanical:
- replace io_priority_class& argument with io_intent* one
- pass intent to lower file (if applicatble)
Dropping the priority manager is:
- git-rm .cc and .hh
- sed out all the #include-s
- fix configure.py and cmakefile
The scylla-gdb.py update is a bit hairry -- it needs to use task queues
list for IO classes names and shares, but to detect it should it checks
for the "commitlog" group is present.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closes#13963
This flag designates that we should consume only one
partition from the underlying reader. This means that
attempts to move to another partition should cause an EOS.
When next_partition is called, the buffer could
contain partition_start and possibly static_row.
In this case clear_buffer_to_next_partition will
not remove anything from the buffer and the
reader position should not change. Before this patch,
however, we used to set _end_of_stream=false,
which violated the forwardable-reader
contract - the data of the next partition
was emitted after the data of the first partition
without intermediate EOS.
This bug was found when debugging
test_make_nonforwardable_from_mutations_as_mutation_source flakiness.
A corresponding focused test_make_forwardable_next_partition
has been added to exercise this problem.
This patch fixes the problem with method fast_forward_to
which is similar to the one with next_partition, no
partition_end should be injected for the partition if
fast_forward_to was called inside it.
Before the patch, nonforwardable reader injected
partition_end unconditionally. This caused problems
in case next_partition() was called, the downstream
reader might have already injected its own
partition_end marker, and the one from nonforwardable
reader was a duplicate.
Fixes: #12249
The patch introduces the _partition_is_open flag,
inject partition_end only if there was some data
in the input reader.
A simple unit test has been added for
the nonforwardable reader which checks this
new behaviour.
Move mutation-related files to a new mutation/ directory. The names
are kept in the global namespace to reduce churn; the names are
unambiguous in any case.
mutation_reader remains in the readers/ module.
mutation_partition_v2.cc was missing from CMakeLists.txt; it's added in this
patch.
This is a step forward towards librarization or modularization of the
source base.
Closes#12788
Since the end bound is exclusive, the end position should be
before_key(), not after_key().
Affects only tests, as far as I know, only there we can get an end
bound which is a clustering row position.
Would cause failures once row cache is switched to v2 representation
because of violated assumptions about positions.
Introduced in 76ee3f029cCloses#11823
Currently injecting a partition-end doesn't update
`_last_uncompacted_kind`, which will allow for a subsequent
`next_partition()` call to trigger injecting a partition-end, leading to
an invalid mutation fragment stream (partition-end after partition-end).
Fix by changing `_last_uncompacted_kind` to `partition_end` when
injecting a partition-end, making subsequent injection attempts noop.
Fixes: #11608
Now that we use emit_only_live_rows::no everywhere we can remove this
template parameters. Only the template parameter is removed, the
internal logic around it is left in place (will be removed in a next
patch), by hard-wiring `only_live()`.
The handle must not point at this reader implementation
after it's destroyed.
This fixes use-after-free when the queue_reader_v2
is destroyed first as repair_writer_impl::_queue_reader,
before repair_writer_impl::_mq is destroyed.
The issue was introduced in 39205917a8
in the definition of `repair_writer_impl`.
Fixes#10528
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
The only user is the tests of downgrade_to_v1(), which uses it through
mutation source. To avoid any new users popping up, we make it a private
method of the latter. In the process the pass-through optimization is
dropped, it is not needed for tests anyway.
The only user is row level repair: it is replaced with
downgrade_to_v1(make_empty_flat_reader_v2()). The row level reader has
lots of downgrade_to_v1() calls, we will deal with these later all at
once.
Another use is the empty mutation source, this is trivially converted to
use the v2 variant.
"
cache_flat_mutation_reader gets a native v2 implementation. The
underlying mutation representation is not changed: range deletions are
still stored as v1 range_tombstones in mutation_partition. These are
converted to range tombstone changes during reading.
This allows for separating the change of a native v2 reader
implementation and a native v2 in-memory storage format, enabling the
two to be done at separate times and incrementally.
This means there is still conversion ingoing when reading from cache and
when populating, but when reading from underlying, the stream can now be
passed through as-is without conversions.
Also, any future v2 related changes to the in-memory storage will now be
limited to the cache reader implementation itself.
In the process, the non-forwarding reader, whose only user is the cache,
is also converted to v2.
"
Performance results reported by Botond:
"
build/release/test/perf/perf_simple_query -c1 -m2G --flush --
duration=20
BEFORE
median 130421.76 tps ( 71.1 allocs/op, 12.1 tasks/op, 47462
insns/op)
median absolute deviation: 319.64
maximum: 131028.33
minimum: 127502.55
AFTER
median 133297.41 tps ( 64.1 allocs/op, 12.2 tasks/op, 45406
insns/op)
median absolute deviation: 2964.24
maximum: 137581.56
minimum: 123739.4
Getting rid of those upgrade/downgrade was good for allocs and ops.
Curiously there is a 0.1 rise in number of tasks though.
"
* 'row-cache-readers-v2/v1' of https://github.com/denesb/scylla:
row_cache: update reader implementations to v2
range_tombstone_change_generator: flush(): add end_of_range
readers/nonforwardable: convert to v2
read_context: fix indentation
read_context: coroutinize move_to_next_partition()
row_cache: cache_entry::read(): return v2 reader
row_cache: return v2 readers from make_reader*()
readers/delegating_v2: s/make_delegating_reader_v2/make_delegating_reader/
It has a single user, the row cache, which for now has to
upgrade/downgrade around the nonforwardable reader, but this will go
away in the next patches when the row cache readers are converted to v2
proper.
Extract the common parts of the single mutation reader
and the vector-based variant into mutation_reader_base
and reuse from both readers.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
slice_mutations() is currently used only by readers/mutation_readers.cc
so there's no need to expose it.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
There are at least 1 actual and 1 potential users for it; this
change converts the existing one.
Signed-off-by: Michael Livshin <michael.livshin@scylladb.com>
"
First migrate all users to the v2 variant, all of which are tests.
However, to be able to properly migrate all tests off it, a v2 variant
of the restricted reader is also needed. All restricted reader users are
then migrated to the freshly introduced v2 variant and the v1 variant is
removed.
Users include:
* replica::table::make_reader_v2()
* streaming_virtual_table::as_mutation_source()
* sstables::make_reader()
* tests
This allows us to get rid of a bunch of conversions on the query path,
which was mostly v2 already.
With a few tests we did kick the can down the road by wrapping the v2
reader in `downgrade_to_v1()`, but this series is long enough already.
Tests: unit(dev), unit(boost/flat_mutation_reader_test:debug)
"
* 'remove-reader-from-mutations-v1/v3' of https://github.com/denesb/scylla:
readers: remove now unused v1 reader from mutations
test: move away from v1 reader from mutations
test/boost/mutation_reader_test: use fragment_scatterer
test/boost/mutation_fragment_test: extract fragment_scatterer into a separate hh
test/boost: mutation_fragment_test: refactor fragment_scatterer
readers: remove now unused v1 reversing reader
test/boost/flat_mutation_reader_test: convert to v2
frozen_mutation: fragment_and_freeze(): convert to v2
frozen_mutation: coroutinize fragment_and_freeze()
readers: migrate away from v1 reversing reader
db/virtual_table: use v2 variant of reversing and forwardable readers
replica/table: use v2 variant of reversing reader
sstables/sstable: remove unused make_crawling_reader_v1()
sstables/sstable: remove make_reader_v1()
readers: add v2 variant of reversing reader
readers/reversing: remove FIXME
readers: reader from mutations: use mutation's own schema when slicing
The only internal user is the v1 make reader from mutations, we use a
downgrade/upgrade to be able to use the v2 reversing reader there. This
is ugly but the v1 reader from mutations is going away soon too, so not
a real problem.
The v2 format allows for a much simpler reversing mechanism since
clustering fragments can simply be reversed as they are read. Fragments
are directly pushed in the reader's buffer eliminating a separate move
phase.
Existing reverse reader unit tests are converted to test the v2 one.
Instead of the schema that is used for the reader. The schema of
individual mutations might be different (albeit compatible) and in debug
mode this can trigger an assert in mutation partition.
By folding the former to the latter. Now that all the readers are nicely
co-located in the same folder, no point in having two distinct logger
for them.
In most files it was unused. We should move these to the patch which
moved out the last interesting reader from mutation_reader.hh (and added
the corresponding new header include) but its probably not worth the
effort.
Some other files still relied on mutation_reader.hh to provide reader
concurrency semaphore and some other misc reader related definitions.
"
The only real user is view building, which is converted to v2 and then
the v1 version of the mutation from fragments reader is removed.
Tests: unit(dev, release)
"
* 'v2-only-from-fragments-mutations/v1' of https://github.com/denesb/scylla:
readers: remove now unused v1 reader from fragments
test/boost: flat_mutation_reader_test: remove reader from fragments test
replica/table: migrate generate_and_propagate_view_updates() to v2
replica/table: migrate populate_views() to v2
db/view: convert view_update_builder interface to v2
db/view: migrate view_update_builder to v2
