The change to use consistency_level::ONE in send_batchlog_mutation
sort of fixes#478, but is not 100% correct.
When doing async_remove_from_batchlog, the CL is actually supposed to
be ANY.
Also, we should _not_ remove the batch log mutation from any nodes
if the mutate fails, since having it there in case of failure is sort of
the whole point of it. I.e. async_remove_from_batchlog should not be
called from a "finally", but from a "then".
Refs #478
From Pawel:
This series enables row cache to serve range queries. In order to achieve
that row cache needs to know whether there are some other partitions in
the specified range that are not cached and need to be read from the sstables.
That information is provied by key_readers, which work very similarly to
mutation_readers, but return only the decorated key of partitions in
range. In case of sstables key_readers is implemented to use partition
index.
Approach like this has the disadvantage of needing to access the disk
even if all partitions in the range are cached. There are (at least) two
solutions ways of dealing with that problem:
- cache partition index - that will also help in all other places where it
is neededed
- add a flag to cache_entry which, when set, indicates that the immediate
successor of the partition is also in the cache. Such flag would be set
by mutation reader and cleared during eviction. It will also allow
newly created mutations from memtable to be moved to cache provided that
both their successors and predecessors are already there.
The key_reader part of this patchsets adds a lot of new code that probably
won't be used in any other place, but the alternative would be to always
interleave reads from cache with reads from sstables and that would be
more heavy on partition index, which isn't cached.
Fixes#185.
The migrator tells lsa how to move an object when it is compacted.
Currently it is a function pointer, which means we must know how to move
the object at compile time. Making it an object allows us to build the
migration function at runtime, making it suitable for runtime-defined types
(such as tuples and user-defined types).
In the future, we may also store the size there for fixed-size types,
reducing lsa overhead.
C++ variable templates would have made this patch smaller, but unfortunately
they are only supported on gcc 5+.
This reader enables range queries on row cache. An underlying key_reader
is used to obtain information about partitions that belong to the
specified range and if any of them isn't in the cache an underlying
mutation reader is used to read the missing data.
Signed-off-by: Paweł Dziepak <pdziepak@scylladb.com>
This mutation reader returns mutations from cache that are in a given
range. There may be other mutations in the system (e.g. in sstables)
that won't be returned, so this reader on its own cannot really satisfy
any query.
Signed-off-by: Paweł Dziepak <pdziepak@scylladb.com>
