MDL BF-BF conflict on ALTER and UPDATE with multi-level foreign key parents #3842
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…arents Issue: Mariadb acquires additional MDL locks on UPDATE/INSERT/DELETE statements on table with foreign keys. For example, table t1 references t2, an UPDATE to t1 will MDL lock t2 in addition to t1. A replica may deliver an ALTER t1 and UPDATE t2 concurrently for applying. Then the UPDATE may acquire MDL lock for t1, followed by a conflict when the ALTER attempts to MDL lock on t1. Causing a BF-BF conflict. Solution: Additional keys for the referenced/foreign table needs to be added to avoid potential MDL conflicts with concurrent update and DDLs.
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Issue:
Mariadb acquires additional MDL locks on UPDATE/INSERT/DELETE statements on table with foreign keys. For example, table t1 references t2, an UPDATE to t1 will MDL lock t2 in addition to t1.
A replica may deliver an ALTER t1 and UPDATE t2 concurrently for applying. Then the UPDATE may acquire MDL lock for t1, followed by a conflict when the ALTER attempts to MDL lock on t1. Causing a BF-BF conflict.
Solution:
Additional keys for the referenced/foreign table needs to be added to avoid potential MDL conflicts with concurrent update and DDLs.
Description
TODO: fill description here
Release Notes
TODO: What should the release notes say about this change?
Include any changed system variables, status variables or behaviour. Optionally list any https://mariadb.com/kb/ pages that need changing.
How can this PR be tested?
TODO: modify the automated test suite to verify that the PR causes MariaDB to behave as intended.
Consult the documentation on "Writing good test cases".
If the changes are not amenable to automated testing, please explain why not and carefully describe how to test manually.
Basing the PR against the correct MariaDB version
mainbranch.PR quality check