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MDEV-34392 Inplace algorithm violates the foreign key constraint

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Don't allow the referencing key column from NULL TO NOT NULL
when

 1) Foreign key constraint type is ON UPDATE SET NULL
 2) Foreign key constraint type is ON DELETE SET NULL
 3) Foreign key constraint type is UPDATE CASCADE and referenced
 column declared as NULL

Don't allow the referenced key column from NOT NULL to NULL
when foreign key constraint type is UPDATE CASCADE
and referencing key columns doesn't allow NULL values

get_foreign_key_info(): InnoDB sends the information about
nullability of the foreign key fields and referenced key fields.

fk_check_column_changes(): Enforce the above rules for COPY
algorithm

innobase_check_foreign_drop_col(): Checks whether the dropped
column exists in existing foreign key relation

innobase_check_foreign_low() : Enforce the above rules for
INPLACE algorithm

dict_foreign_t::check_fk_constraint_valid(): This is used
by CREATE TABLE statement to check nullability for foreign
key relation.
This commit is contained in:
Thirunarayanan Balathandayuthapani
2024-09-30 13:37:26 +05:30
parent 45298b730b
commit cc810e64d4
18 changed files with 919 additions and 215 deletions
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2
mysql-test/suite/innodb/r/innodb.result
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@@ -3057,7 +3057,7 @@ ALTER TABLE t2 ADD FOREIGN KEY (a) REFERENCES t1 (a) ON DELETE SET NULL;
set @old_sql_mode = @@sql_mode;
set @@sql_mode = 'STRICT_TRANS_TABLES';
ALTER TABLE t2 MODIFY a INT NOT NULL;
ERROR HY000: Column 'a' cannot be NOT NULL: needed in a foreign key constraint 'test/t2_ibfk_1' SET NULL
ERROR HY000: Column 'a' cannot be NOT NULL: needed in a foreign key constraint 't2_ibfk_1' SET NULL
set @@sql_mode = @old_sql_mode;
DELETE FROM t1;
DROP TABLE t2,t1;