Commit 968177da04 has changed the schema
of cdc_topology_description and cdc_description tables in the
system_distributed keyspace.
Unfortunately this was a backwards-incompatible change: these tables
would always be created, irrespective of whether or not "experimental"
was enabled. They just wouldn't be populated with experimental=off.
If the user now tries to upgrade Scylla from a version before this change
to a version after this change, it will work as long as CDC is protected
b the experimental flag and the flag is off.
However, if we drop the flag, or if the user turns experimental on,
weird things will happen, such as nodes refusing to start because they
try to populate cdc_topology_description while assuming a different schema
for this table.
The simplest fix for this problem is to rename the tables. This fix must
get merged in before CDC goes out of experimental.
If the user upgrades his cluster from a pre-rename version, he will simply
have two garbage tables that he is free to delete after upgrading.
sstables and digests need to be regenerated for schema_digest_test since
this commit effectively adds new tables to the system_distributed keyspace.
This doesn't result in schema disagreement because the table is
announced to all nodes through the migration manager.
Some legacy `mc` SSTables (created in Scylla 3.0) may contain incorrect
serialization headers, which don't wrap frozen UDTs nested inside collections
with the FrozenType<...> tag. When reading such SSTable,
Scylla would detect a mismatch between the schema saved in schema
tables (which correctly wraps UDTs in the FrozenType<...> tag) and the schema
from the serialization header (which doesn't have these tags).
SSTables created in Scylla versions 3.1 and above, in particular in
Scylla versions that contain this commit, create correct serialization
headers (which wrap UDTs in the FrozenType<...> tag).
This commit does two things:
1. for all SSTables created after this commit, include a new feature
flag, CorrectUDTsInCollections, presence of which implies that frozen
UDTs inside collections have the FrozenType<...> tag.
2. when reading a Scylla SSTable without the feature flag, we assume that UDTs
nested inside collections are always frozen, even if they don't have
the tag. This assumption is safe to be made, because at the time of
this commit, Scylla does not allow non-frozen (multi-cell) types inside
collections or UDTs, and because of point 1 above.
There is one edge case not covered: if we don't know whether the SSTable
comes from Scylla or from C*. In that case we won't make the assumption
described in 2. Therefore, if we get a mismatch between schema and
serialization headers of a table which we couldn't confirm to come from
Scylla, we will still reject the table. If any user encounters such an
issue (unlikely), we will have to use another solution, e.g. using a
separate tool to rewrite the SSTable.
Fixes#6130.
The cdc_topology_description table will be used internally
by nodes to send new CDC stream generations to other nodes.
The cdc_description table is a user-facing table,
used to inform users about new sets of CDC streams.
Regenerate sstables and digests for schema_change_test.
We don't need to protect this change by a schema feature:
when a node creates these tables, it announces them
to all other nodes. If schema agreement happens before
this migration, all nodes will use a digest calculated
without these tables. If it happens after, then all nodes
will eventually know about these tables and use a digest
calculated with these tables.
The original "test_schema_digest_does_not_change" test case ensures
that schema digests will match for older nodes that do not support
all the features yet (including computed columns).
The additional case uses sstables generated after CDC was enabled
and a table with CDC enabled is created,
in order to make sure that the digest computed
including CDC column does not change spuriously as well.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
The plan is to move the unstructured content of tests/ directory
into the following directories of test/:
test/lib - shared header and source files for unit tests
test/boost - boost unit tests
test/unit - non-boost unit tests
test/manual - tests intended to be run manually
test/resource - binary test resources and configuration files
In order to not break git bisect and preserve the file history,
first move most of the header files and resources.
Update paths to these files in .cc files, which are not moved.
