Until recently, we believed that range tombstones we read from sstables will
always be for entire rows (or more generalized clustering-key prefixes),
not for arbitrary ranges. But as we found out, because Cassandra insists
that range tombstones do not overlap, it may take two overlapping row
tombstones and convert them into three range tombstones which look like
general ranges (see the patch for a more detailed example).
Not only do we need to accept such "split" range tombstones, we also need
to convert them back to our internal representation which, in the above
example, involves two overlapping tombstones. This is what this patch does.
This patch also contains a test for this case: We created in Cassandra
an sstable with two overlapping deletions, and verify that when we read
it to Scylla, we get these two overlapping deletions - despite the
sstable file actually having contained three non-overlapping tombstones.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <b7c07466074bf0db6457323af8622bb5210bb86a.1459399004.git.glauber@scylladb.com>
For simplicity, we want to have keys serializable and deserializable
without schema for now. We will serialize keys in a generic form of a
vector of components where the format of components is specified by
CQL binary protocol. So conversion between keys and vector of
components needs to be possible to do without schema.
We may want to make keys schema-dependent back in the future to apply
space optimizations specific to column types. Existing code should
still pass schema& to construct and access the key when possible.
One optimization had to be reverted in this change - avoidance of
storing key length (2 bytes) for single-component partition keys. One
consequence of this, in addition to a bit larger keys, is that we can
no longer avoid copy when constructing single-component partition keys
from a ready "bytes" object.
I haven't noticed any significant performance difference in:
tests/perf/perf_simple_query -c1 --write
It does ~130K tps on my machine.
Its definition as a lambda function is inconvenient, because it does not allow
us to use default values for parameters.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
The intent is to make data returned by queries always conform to a
single schema version, which is requested by the client. For CQL
queries, for example, we want to use the same schema which was used to
compile the query. The other node expects to receive data conforming
to the requested schema.
Interface on shard level accepts schema_ptr, across nodes we use
table_schema_version UUID. To transfer schema_ptr across shards, we
use global_schema_ptr.
Because schema is identified with UUID across nodes, requestors must
be prepared for being queried for the definition of the schema. They
must hold a live schema_ptr around the request. This guarantees that
schema_registry will always know about the requested version. This is
not an issue because for queries the requestor needs to hold on to the
schema anyway to be able to interpret the results. But care must be
taken to always use the same schema version for making the request and
parsing the results.
Schema requesting across nodes is currently stubbed (throws runtime
exception).
Since bytes is a very generic value that is returned from many calls,
it is easy to pass it by mistake to a function expecting a data_value,
and to get a wrong result. It is impossible for the data_value constructor
to know if the argument is a genuine bytes variable, a data_value of another
type, but serialized, or some other serialized data type.
To prevent misuse, make the data_value(bytes) constructor
(and complementary data_value(optional<bytes>) explicit.
We use boost::any to convert to and from database values (stored in
serlialized form) and native C++ values. boost::any captures information
about the data type (how to copy/move/delete etc.) and stores it inside
the boost::any instance. We later retrieve the real value using
boost::any_cast.
However, data_value (which has a boost::any member) already has type
information as a data_type instance. By teaching data_type intances about
the corresponding native type, we can elimiante the use of boost::any.
While boost::any is evil and eliminating it improves efficiency somewhat,
the real goal is growing native type support in data_type. We will use that
later to store native types in the cache, enabling O(log n) access to
collections, O(1) access to tuples, and more efficient large blob support.
This patch tests that collection within a mutation behave properly.
That is what lead to #188.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Using a lambda for implementing a mutation_reader is nifty, but does not
allow us to add methods.
Switch to a class-based implementation in anticipation of adding a close()
method.
When a schema is available, we use it. However, we have, by now, way too many
tests. Some of them use tables for which we don't even know the schema. It would
have been a massive amount of work to require a schema for all of them - so I am
keeping both constructors around.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
