On Thu, Dec 30, 2021 at 06:45:30AM +0000, houzj.f...@fujitsu.com wrote: > I think forbids DROP INDEX might not completely solve this problem. Because > user could still use other command to delete the index, for example: ALTER > TABLE DROP COLUMN. After dropping the column, the index on it will also be > dropped. > > Besides, user can also ALTER REPLICA IDENTITY USING INDEX "primary key", and > in > this case, when they ALTER TABLE DROP CONSTR "PRIMARY KEY", the replica > identity index will also be dropped.
Indexes related to any other object type, like constraints, are dropped as part of index_drop() as per the handling of dependencies. So, by putting a restriction there, any commands would take this code path, and fail when trying to drop an index used as a replica identity. Why would that be logically a problem? We may want errors with more context for such cases, though, as complaining about an object not directly known by the user when triggering a different command, like a constraint index, could be confusing. -- Michael
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