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MDL BF-BF conflict on ALTER and UPDATE with multi-level foreign key parents #479

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MDL BF-BF conflict on ALTER and UPDATE with multi-level foreign key parents #479

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Issue:
Mariadb acquires additional MDL locks on UPDATE 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.

sciascid and others added 4 commits January 21, 2025 14:19
@sciascid
MDEV-35018 MDL BF-BF conflict on DROP TABLE
63c4d72 
DROP TABLE on child and UPDATE of parent table can cause an MDL BF-BF
conflict when applied concurrently.
DROP TABLE takes MDL locks on both child and its parent table, however
it only it did not add certification keys for the parent table.
This patch adds the following:
 * Append certification keys corresponding to all parent tables
   before DROP TABLE replication.
 * Fix wsrep_append_fk_parent_table() so that it works when it is
   given a table list containing temporary tables.
 * Make sure function wsrep_append_fk_parent_table() is only called
   for local transaction. That was not the case for ALTER TABLE.
 * Add a test case that verifies that UPDATE parent depends on
   preceeding DROP TABLE child.
 * Adapt galera_ddl_fk_conflict test to work with DROP TABLE as well.
@hemantdangi-gc
MDL BF-BF conflict on ALTER and UPDATE with multi-level foreign key p…
c7a4ec5 
…arents

Issue:
Mariadb acquires additional MDL locks on UPDATE 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.
@hemantdangi-gc
Revert "MDL BF-BF conflict on ALTER and UPDATE with multi-level forei…
ec10115 
…gn key p…"

This reverts commit c7a4ec5.
@hemantdangi-gc
MDL BF-BF conflict on ALTER and UPDATE with multi-level foreign key p…
190be96 
…arents

Issue:
Mariadb acquires additional MDL locks on UPDATE 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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2 participants
@hemantdangi-gc @sciascid