Description:
Engine considers hidden part of key (columns from primary key which are implicitly added to secondary keys) when determines if it can serve as parent. Example: InnoDB.
If the FOREIGN KEY of the child table which references the hidden part of parent table's UK should not have the same name as the parent table's UK.
Because the number of columns of child table's foreign key is greater than the number of columns of parent table's key.
They are different.
```
typedef struct Table_share_foreign_key_info {
LEX_CSTRING referenced_table_db;
LEX_CSTRING referenced_table_name;
/**
Name of unique key matching FK in parent table, "" if there is no
unique key.
*/
LEX_CSTRING unique_constraint_name;
dd::Foreign_key::enum_rule update_rule, delete_rule;
uint columns;
/**
Arrays with names of referencing columns of the FK.
*/
LEX_CSTRING *column_name;
} TABLE_SHARE_FOREIGN_KEY_INFO;
```
How to repeat:
CREATE TABLE t1 (a INT, c INT, UNIQUE KEY(c), PRIMARY KEY (a));
CREATE TABLE t2 (fk1 INT, fk2 INT, FOREIGN KEY (fk1, fk2) REFERENCES t1 (c, a));
SELECT * from information_schema.referential_constraints\G
*************************** 1. row ***************************
CONSTRAINT_CATALOG: def
CONSTRAINT_SCHEMA: test
CONSTRAINT_NAME: t2_ibfk_1
UNIQUE_CONSTRAINT_CATALOG: def
UNIQUE_CONSTRAINT_SCHEMA: test
UNIQUE_CONSTRAINT_NAME: c
MATCH_OPTION: NONE
UPDATE_RULE: NO ACTION
DELETE_RULE: NO ACTION
TABLE_NAME: t2
REFERENCED_TABLE_NAME: t1
1 row in set (0.01 sec)
The unique_constraint_name of child table's FOREIGN KEY in table_share is 'c'. However, the FOREIGN KEY has two columns.
Suggested fix:
When not all unique key columns are referenced, set unique_constraint_name to "".
Description: Engine considers hidden part of key (columns from primary key which are implicitly added to secondary keys) when determines if it can serve as parent. Example: InnoDB. If the FOREIGN KEY of the child table which references the hidden part of parent table's UK should not have the same name as the parent table's UK. Because the number of columns of child table's foreign key is greater than the number of columns of parent table's key. They are different. ``` typedef struct Table_share_foreign_key_info { LEX_CSTRING referenced_table_db; LEX_CSTRING referenced_table_name; /** Name of unique key matching FK in parent table, "" if there is no unique key. */ LEX_CSTRING unique_constraint_name; dd::Foreign_key::enum_rule update_rule, delete_rule; uint columns; /** Arrays with names of referencing columns of the FK. */ LEX_CSTRING *column_name; } TABLE_SHARE_FOREIGN_KEY_INFO; ``` How to repeat: CREATE TABLE t1 (a INT, c INT, UNIQUE KEY(c), PRIMARY KEY (a)); CREATE TABLE t2 (fk1 INT, fk2 INT, FOREIGN KEY (fk1, fk2) REFERENCES t1 (c, a)); SELECT * from information_schema.referential_constraints\G *************************** 1. row *************************** CONSTRAINT_CATALOG: def CONSTRAINT_SCHEMA: test CONSTRAINT_NAME: t2_ibfk_1 UNIQUE_CONSTRAINT_CATALOG: def UNIQUE_CONSTRAINT_SCHEMA: test UNIQUE_CONSTRAINT_NAME: c MATCH_OPTION: NONE UPDATE_RULE: NO ACTION DELETE_RULE: NO ACTION TABLE_NAME: t2 REFERENCED_TABLE_NAME: t1 1 row in set (0.01 sec) The unique_constraint_name of child table's FOREIGN KEY in table_share is 'c'. However, the FOREIGN KEY has two columns. Suggested fix: When not all unique key columns are referenced, set unique_constraint_name to "".