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79cf277ea2
Currently we diff schemas based on table/view name, and if the names
match, then we detect altered schemas by comparing the schema
mutations. This fails to detect transitions which involve dropping and
recreating a schema with the same name, if a node receives these
notifications simultaneously (for example, if the node was temporarily
down or partitioned).
Note that because the ID is persisted and created when executing a
create_table_statement, then even if a schema is re-created with the
exact same structure as before, we will still considered it altered
because the mutations will differ.
This also stops schema pulling from working, since it relies on schema
merging.
The solution is to diff schemas using their ID, and not their name.
Keyspaces and user types are also susceptible to this, but in their
case it's fine: these are values with no identity, and are just
metadata. Dropping and recreating a keyspace can be views as dropping
all tables from the keyspace, altering it, and eventually adding new
tables to the keyspace.
Note that this solution doesn't apply to tables dropped and created
with the same ID (using the `WITH ID = {}` syntax). For that, we would
need to detect deltas instead of applying changes and then reading the
new state to find differences. However, this solution is enough,
because tables are usually created with ID = {} for very specific,
peculiar reasons. The original motivation meant for the new table to
be treated exactly as the old, so the current behavior is in fact the
desired one.
Tests: unit(release), dtests(schema_test, schema_management_test)
Fixes #3797
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Message-Id: <20181001230932.47153-2-duarte@scylladb.com>
(cherry picked from commit 40a30d4129)