[datatype] fix equals method for udt datatypes across schema upgrades #531
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Thinking about this more, I think that although this is semantically correct for |
| // newer 'version' of the UDT data type after a schema change event should be | ||
| // treated as equivalent in this scenario, by simply looking at the first N | ||
| // mutual fields they should share. | ||
| size_t min_fields_size = std::min(fields_.size(), user_type->fields_.size()); |
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This seems reasonable to me. It does seem that after creating a type that a type can only be altered in the following ways:
- Rename field:
ALTER TYPE address RENAME zip TO zipcode AND street_name TO street - Add a field:
ALTER TYPE address ADD country text
It'd be nice to have some tests that verify this is a correct assumption.
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It'd be nice to have some tests that verify this is a correct assumption.
I'm not entirely sure how we would test that? Are you suggesting we try to test that the database rejects invalid DDL?
There is a third way, you can change the type of a field ALTER field_name TYPE new_cql_datatype - however, I think if you're doing this, you probably need to redeploy your application anyways since the types are changing.
What do you think about my second comment? Should I instead refactor this into a "is valid data type for" method, that way equals still remains an equality check? Additionally, if that's the case, we can drop the name check on the field, this will allow us to handle renaming of a field, and still considering them equal. |
We encountered a bug with this driver, where an altered UDT would cause
cass_statement_bind_user_type_by_name_nto fail on a prepared statement that was prepared prior to the db altered.I think that this should be a sensible fix, it for sure fixes our issue... however, I have no idea if this is actually sound!
Unfortunately I do not have a C++ reproducer for this bug, since we use the rust wrapper to this driver, that reproducer is here: https://gist.github.com/jhgg/d009d1fb994a0fd550bd01bb803baee5