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Type: Improvement
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Resolution: Unresolved
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Priority: Major - P3
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None
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Affects Version/s: None
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Component/s: Storage
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Catalog and Routing
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Fully Compatible
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0
Currently, the kv engine does not check to see if a database is empty after a collection drop. Thus, empty databases can persist until mongod restarts (or the catalog is reloaded via replication rollback to stable timestamp). This situation is usually benign, but a database entry's presence does do one thing: it enforces that no other databases that are spelled the same but differ in capitalization can be created.
Because recover-to-timestamp exists, it can result in some replica set nodes having a catalog entry for an empty database while other nodes do not have such an entry. This can result in the ability to crash secondary nodes that have an empty database entry that a primary node does not have - by attempting to create a database with a different case than the existing empty database entry.
To fix this, we can check to see if a database is empty (i.e., no collection entries remain in the catalog) after a collection drop. If it is indeed empty, we can attempt to close the database by locking it in X mode and calling DatabaseHolder::close().
- depends on
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SERVER-43890 Remove two-phase database drops
- Closed
- is depended on by
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SERVER-76342 Drop system.views when the last view is removed
- Blocked
- is related to
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SERVER-77281 Investigate removing use of the DatabaseHolder and/or dropDatabase oplog entry in the storage execution layer
- Closed
- related to
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SERVER-85975 Clear database state when dropping last collection
- Open
- split from
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SERVER-33272 The DatabaseHolder::close() function no longer requires a global write lock and neither does the dropDatabase command.
- Closed