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.
query::result transformation to printable form is very heavy operation
that allocates memory and thus can fail. Add a class to query::result that
can be used with logger to push to string conversion when output is
performed.
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>
Result digest is going to be computed in query result builder and
require information not available in the query resylt. That's why the
digest now needs to be sent to the other nodes together with the result
as they won't be able compute it on their own.
Signed-off-by: Paweł Dziepak <pdziepak@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
That's what we're trying to standardize on.
This patch also fixes an issue with current query::result::serialize()
not being const-qualified, because it modifies the
buffer. messaging_service did a const cast to work this around, which
is not safe.
Works only if all replicas (participating in CL) has the same live
data. Does not detects mismatch in tombstones (no infrastructure yet).
Does not report timeout yet.
