Reversed iterators are adaptors for 'normal' iterators. These underlying
iterators point to different objects that the reversed iterators
themselves.
The consequence of this is that removing an element pointed to by a
reversed iterator may invalidate reversed iterator which point to a
completely different object.
This is what happens in trim_rows for reversed queries. Erasing a row
can invalidate end iterator and the loop would fail to stop.
The solution is to introduce
reversal_traits::erase_dispose_and_update_end() funcion which erases and
disposes object pointed to by a given iterator but takes also a
reference to and end iterator and updates it if necessary to make sure
that it stays valid.
Fixes#1609.
Signed-off-by: Paweł Dziepak <pdziepak@scylladb.com>
Message-Id: <1472080609-11642-1-git-send-email-pdziepak@scylladb.com>
(cherry picked from commit 6012a7e733)
The patch calculates row count during result building and while merging.
If one of results that are being merged does not have row count the
merged result will not have one either.
Broken by f15c380a4f.
This resulted in empty collection being returned in the results
instead of no collection.
Fixes org.apache.cassandra.cql3.validation.entities.CollectionsTest
from cassandra-unit-tests.
Reproduced by dtest paging_test.py:TestPagingData.static_columns_paging_test.
Broken by f15c380a4f, where the
calcualtion of has_ck_selector got broken, in such a way that present
clustering restrictions were treated as if not present, which resulted
in static row being returned when it shouldn't.
While at it, unify the check between query_compacted() and
do_compact() by extracting it to a function.
The first erase_and_dispose(), which removes rows between last
position and beginning of the next range, can invalidate end()
iterator of the range. Fix by looking up end after erasing.
mutation_partition::range() was split into lower_bound() and
upper_bound() to allow for that.
This affects for example queries with descending order where the
selected clustering range is empty and falls before all rows.
Exposed by f15c380a4f, which is now
calling do_compact() during query.
Reproduced by dtest paging_test.py:TestPagingData.static_columns_paging_test
"Currently data query digest includes cells and tombstones which may have
expired or be covered by higher-level tombstones. This causes digest
mismatch between replicas if some elements are compacted on one of the
nodes and not on others. This mismatch triggers read-repair which doesn't
resolve because mutations received by mutation queries are not differing,
they are compacted already.
The fix adds compacting step before writing and digesting query results by
reusing the algorithm used by mutation query. This is not the most optimal
way to fix this. The compaction step could be folded with the query writing,
there is redundancy in both steps. However such change carries more risk,
and thus was postponed.
perf_simple_query test (cassandra-stress-like partitions) shows regression
from 83k to 77k (7%) ops/s.
Fixes #1165."
Currently data query digest includes cells and tombstones which may have
expired or be covered by higher-level tombstones. This causes digest
mismatch between replicas if some elements are compacted on one of the
nodes and not on others. This mismatch triggers read-repair which doesn't
resolve because mutations received by mutation queries are not differing,
they are compacted already.
The fix adds compacting step before writing and digesting query results by
reusing the algorithm used by mutation query. This is not the most optimal
way to fix this. The compaction step could be folded with the query writing,
there is redundancy in both steps. However such change carries more risk,
and thus was postponed.
perf_simple_query test (cassandra-stress-like partitions) shows regression
from 83k to 77k (7%) ops/s.
Fixes#1165.
We cannot leave partially applied mutation behind when the write
fails. It may fail if memory allocation fails in the middle of
apply(). This for example would violate write atomicity, readers
should either see the whole write or none at all.
This fix makes apply() revert partially applied data upon failure, by
the means of ReversiblyMergeable concept. In a nut shell the idea is
to store old state in the source mutation as we apply it and swap back
in case of exception. At cell level this swapping is inexpensive, just
rewiring pointers. For this to work, the source mutation needs to be
brought into mutable form, so frozen mutations need to be unfrozen. In
practice this doesn't increase amount of cell allocations in the
memtable apply path because incoming data will usually be newer and we
will have to copy it into LSA anyway. There are extra allocations
though for the data structures which holds cells.
I didn't see significant change in performance of:
build/release/tests/perf/perf_simple_query -c1 -m1G --write --duration 13
The score fluctuates around ~77k ops/s.
Fixes#283.
Currently only "set" storage could store empty cells, but not the
"vector" one because there empty cell has the meaning of being
missing. To implement rolback, we need to be able to distinguish empty
cells from missing ones. Solve by making vector storage use a bitmap
for presence checking instead of emptiness. This adds 4 bytes to
vector storage.
Query result digest is used to verify that all replicas have the same
data. Therefore, it needs to contain more information than the query
result itself in order to ensure proper detection of disagreements.
Generally, adding clustering keys to the digest regardless of whether
the client asked for them will guarantee correctness. However, adding
tombstones as well improves the chances of early detection of nodes
containing stale data.
Signed-off-by: Paweł Dziepak <pdziepak@scylladb.com>
This patch change the way optional vector are implemented.
Now a vector of optional would be handle like any other non primitive
types, with a single method add() that would return a writer to the
optional.
The writer to the optional would have a skip and write method like
simple optional field.
For basic types the write method would get the value as a parameter, for
composite type, it would return a writer to the type.
Signed-off-by: Amnon Heiman <amnon@scylladb.com>
Message-Id: <1456796143-3366-2-git-send-email-amnon@scylladb.com>
The query result footprint for cassandra-stress mutation as reported
by tests/memory-footprint increased by 18% from 285 B to 337 B.
perf_simple_query shows slight regression in throughput (-8%):
build/release/tests/perf/perf_simple_query -c4 -m1G --partitions 100000
Before: ~433k tps
After: ~400k tps
From Avi:
This patchset introduces a linearization context for managed_bytes objects.
Within this context, any scattered managed_bytes (found only in lsa regions,
so limited to memtable and cache) are auto-linearized for the lifetime of
the context. This ensures that key and value lookups can use fast
contiguous iterators instead of using slow discontiguous iterators (or
crashing, as is the case now).
We want the format of query results to be eventually defined in the
IDL and be independent of the format we use in memory to represent
collections. This change is a step in this direction.
The change decouples format of collection cells in query results from
our in-memory representation. We currently use collection_mutation_view,
after the change we will use CQL binary protocol format. We use that because
it requires less transformations on the coordinator side.
One complication is that some list operations need to retrieve keys
used in list cells, not only values. To satisfy this need, new query
option was added called "collections_as_maps" which will cause lists
and sets to be reinterpreted as maps matching their underlying
representation. This allows the coordinator to generate mutations
referencing existing items in lists.
Schema is tracked in memtable and cache per-entry. Entries are
upgraded lazily on access. Incoming mutations are upgraded to table's
current schema on given shard.
Mutating nodes need to keep schema_ptr alive in case schema version is
requested by target node.
do_compact() wasn't removing an empty row that is covered by a
tombstone. As a result, an empty partition could be written to a
sstable. To solve this problem, let's make trim_rows remove a
row that is considered to be empty. A row is empty if it has no
tombstone, no marker and no cells.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Fixes#589
If we got no rows, but have live static columns, we should only
give them back IFF we did not have any CK restrictions.
If ck:s exist, and we have a restriction on them, we either have maching
rows, or return nothing, since cql does not allow "is null".
Apparently, link hook copy constructor is a no-op and move contructor
doesn't exist so the code is correct, but that explicit move makes code
needlessly confusing.
Signed-off-by: Paweł Dziepak <pdziepak@scylladb.com>
The default move assignment operator calls boost::intrusive::set's move
assignment operator, which leaks, because it does not believe it owns
the data.
Fix by providing a custom implementation.
Schemas using compact storage can have clustering keys with the trailing
components not set and effectively being a clustering key prefixes
instead of full clustering keys.
Signed-off-by: Paweł Dziepak <pdziepak@scylladb.com>
Allows for having more than one clustering row range set, depending on
PK queried (although right now limited to one - which happens to be exactly
the number of mutiplexing paging needs... What a coincidence...)
Encapsulates the row_ranges member in a query function, and if needed holds
ranges outside the default one in an extra object.
Query result::builder::add_partition now fetches the correct row range for
the partition, and this is the range used in subsequent iteration.
"This series add code for computing mutation_partition difference.
For mutations A and B:
diffA = A.difference(B);
diffB = B.difference(A);
AB = A.apply(B);
diffA is the minimal mutation that when applied to B makes it equal
to AB and diffB is the minimal mutation that applied to A results in AB.
Fixes #430."
