Schema of system tables is defined statically and table_schema_version needs to be explicitly set in code like this:
```
builder.with_version(system_keyspace::generate_schema_version(table_id, version_offset));
```
Whenever schema is changed, the schema version needs to change, otherwise we hit undefined behavior when trying to interpret mutation data created with the old schema using the new schema.
It's not obvious that one needs to do that and developers often forget to do that. There were several instances of mistakes of omission, some caught during review, some not, e.g.: 31ea74b96e.
This patch changes definitions to call the new `schema_builder::with_hash_version()`, which will make the schema builder compute version from schema definition so that changes of the schema will automatically change the version. This way we no longer rely on the developer to remember to bump the version offset.
All nodes should arrive at the same version, which is verified by existing `test_group0_schema_versioning` and a new unit test: `test_system_schema_version_is_stable`.
Closesscylladb/scylladb#21602
* github.com:scylladb/scylladb:
system_tables: Compute schema version automatically
schema_builder: Introduce with_hash_version()
schema: Store raw_view_info in schema::raw_schema
schema: Remove dead comment
hashing: Add hasher for unordered_map
hashing: Add hasher for unique_ptr
hashing: Add hasher for double
[avi: add missing include <memory> to hashing.hh]
before this change, we rely on `seastar/util/std-compat.hh` to
include the used headers provided by stdandard library. this was
necessary before we moved to a C++20 compliant standard library
implementation. but since Seastar has dropped C++17 support. its
`seastar/util/std-compat.hh` is not responsible for providing these
headers anymore.
so, in this change, we include the used headers directly instead
of relying on `seastar/util/std-compat.hh`.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#18883
And a more specific HasherReturningBytes for hashers
that return bytes in finalize().
HasherReturning will be used by the following patch
also for simple hashers that return size_t from
finalize().
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
