#include "sql/sql_foreign_key_constraint.h"
#include <set>
#include "scope_guard.h"
#include "sql/dd/dd.h"
#include "sql/dd/dd_table.h"
#include "sql/dd/dictionary.h"
#include "sql/dd/types/foreign_key.h"
#include "sql/dd/types/foreign_key_element.h"
#include "sql/field.h"
#include "sql/histograms/table_histograms.h"
#include "sql/key.h"
#include "sql/mysqld.h"
#include "sql/sql_base.h"
#include "sql/sql_class.h"
#include "sql/table.h"

Classes
class	Foreign_key_chain
	Class to store all foreign key names during CASCADE. More...

class	No_fk_checks_guard
	Helper to temporarily enable OPTION_NO_FOREIGN_KEY_CHECKS within a scope and restore the thread option bits during exit. More...

Functions
static bool	check_all_child_fk_ref (THD thd, const TABLE table_p, enum_fk_dml_type dml_type, Foreign_key_chain *chain)
	Check all foreign key constraints on child tables for DML operation on a parent table. More...

static std::string	build_fk_error_message (THD thd, bool check_child_access, bool check_parent_access, const TABLE tbl, TABLE_SHARE_FOREIGN_KEY_INFO *fk)
	Helper function to prepare error message. More...

static bool	report_row_referenced_error (THD thd, const TABLE table_c, TABLE_SHARE_FOREIGN_KEY_INFO *fk)
	Reports ER_ROW_IS_REFERENCED_2 error with fk information. More...

static bool	report_no_referenced_row_error (THD thd, const TABLE table_c, TABLE_SHARE_FOREIGN_KEY_INFO *fk)
	Reports ER_NO_REFERENCED_ROW_2 error with fk information. More...

static TABLE *	find_fk_table_from_open_tables (THD thd, const char db_name, const char table_name, const char fk_name)
	Find TABLE instance of a foreign key table from the THD::open_tables list. More...

static uint	get_key_index (const TABLE table, uint num_columns, LEX_CSTRING col_names)
	Function to get index of key matching col_names in keys list. More...

static bool	is_column_updated (const TABLE table, uint num_key_cols, LEX_CSTRING col_names)
	Function to check if any of the foreign key columns updated. More...

static bool	is_self_fk_value_same (const TABLE table_c, TABLE_SHARE_FOREIGN_KEY_INFO fk)
	Function to check value of foreign key columns and parent columns are same in case self referencing foreign key. More...

static bool	check_and_acquire_MDL_lock (THD thd, const char db_name, const char *table_name, enum_mdl_type mdl_type)
	Check if MDL lock is already acquired on the table. More...

static TABLE *	open_table_for_fk (THD thd, const char db_name, const char *table_name)
	Function to open table for foreign key validation. More...

static bool	is_fk_cascade (TABLE table, enum_fk_dml_type dml_type, const char fk_name)
	Function to check if CASCADE action is defined for a foreign key on UPDATE or DELETE operations. More...

static bool	get_foreign_key_table (THD thd, const char db_name, const char table_name, const char fk_name, enum_fk_dml_type dml_type, bool open_table, TABLE *table, bool table_exists, bool *is_table_opened)
	Function to get TABLE instance of a other table in FK relationship. More...

static bool	set_updated_key_value (THD thd, TABLE table_c, int child_key_idx, const TABLE table_p, int parent_key_idx, TABLE_SHARE_FOREIGN_KEY_INFO fk)
	Function to copy value to child table columns during UPDATE CASCADE operation. More...

static bool	set_key_value_null (TABLE table, uint num_key_cols, LEX_CSTRING col_names)
	Function to set the null value for key columns. More...

bool	is_cascade_from_parent_legal (const TABLE table_p, const KEY key_info_p, const KEY *key_info_c)
	Determine whether a cascaded update from the current state of the parent table record's foreign keys to the corresponding child table's foreign keys is legal. More...

static bool	on_delete_on_update_restrict_or_no_action (THD thd, const TABLE table_c, TABLE_SHARE_FOREIGN_KEY_INFO *fk_c, enum_fk_dml_type dml_type)
	Helper function to apply ON DELETE/ON UPDATE RESTRICT or NOACTION to child table on DML operation. More...

static bool	on_delete_cascade (THD thd, TABLE table_c, TABLE_SHARE_FOREIGN_KEY_INFO fk_c, enum_fk_dml_type dml_type, uchar key_value, int key_len, Foreign_key_chain chain, int error)
	Helper function to apply ON DELETE CASCADE to child table on DML operation. More...

static bool	on_update_cascade (THD thd, const TABLE table_p, TABLE table_c, TABLE_SHARE_FOREIGN_KEY_INFO fk_c, KEY key_info_p, uint parent_key_idx, KEY key_info_c, uint child_key_idx, enum_fk_dml_type dml_type, uchar key_value, int key_len, Foreign_key_chain chain, int *error)
	Function to apply ON UPDATE CASCADE to child table on DML operation. More...

static bool	on_delete_on_update_set_null (THD thd, const TABLE table_p, TABLE table_c, TABLE_SHARE_FOREIGN_KEY_INFO fk_c, enum_fk_dml_type dml_type, uchar key_value, int key_len, Foreign_key_chain chain, int *error)
	Helper function to apply ON DELETE/ON UPDATE SET NULL to child table on DML operation. More...

static bool	check_child_fk_ref (THD thd, const TABLE table_p, TABLE table_c, TABLE_SHARE_FOREIGN_KEY_INFO fk_c, enum_fk_dml_type dml_type, Foreign_key_chain *chain)
	Checks foreign key constraint on child table. More...

static bool	check_parent_fk_ref (THD thd, const TABLE table_c, TABLE table_p, TABLE_SHARE_FOREIGN_KEY_INFO fk, enum_fk_dml_type dml_type)

static bool	skip_foreign_key_checks (THD thd, const TABLE table)
	Helper function to skip foreign checks. More...

bool	check_all_parent_fk_ref (THD thd, const TABLE table_c, enum_fk_dml_type dml_type)
	Check all foreign key constraints on parent tables for DML operation on a child table. More...

bool	check_all_child_fk_ref (THD thd, const TABLE table, enum_fk_dml_type dml_type)
	Check all foreign key constraints on child tables for DML operation on a parent table. More...

bool	is_foreign_key_table_opened (THD thd, const char db_name, const char table_name, const char fk_name)
	Check if TABLE instance for foreign key is already opened. More...

Variables
constexpr uint32_t	FK_MAX_CASCADE_DEPTH = 15
	With the ON CASCADE DELETE/UPDATE clause, deleting from the parent table can trigger recursive cascading calls. More...

Function Documentation

◆ build_fk_error_message()

static std::string build_fk_error_message	(	THD *	thd,
		bool	check_child_access,
		bool	check_parent_access,
		const TABLE *	tbl,
		TABLE_SHARE_FOREIGN_KEY_INFO *	fk
	)

static

Helper function to prepare error message.

Parameters

thd	Thread handle.
check_child_access	Check child table privileges.
check_parent_access	Check parent table privileges.
tbl	TABLE instance.
fk	Foreign Key Info instance.

Returns: std::string Error message.

◆ check_all_child_fk_ref() [1/2]

bool check_all_child_fk_ref	(	THD *	thd,
		const TABLE *	table_p,
		enum_fk_dml_type	dml_type
	)

Check all foreign key constraints on child tables for DML operation on a parent table.

Parameters

thd	Thread handle.
table_p	TABLE instance of a parent table.
dml_type	DML operation type.

Returns: true On error.; false On Success.

◆ check_all_child_fk_ref() [2/2]

static bool check_all_child_fk_ref	(	THD *	thd,
		const TABLE *	table_p,
		enum_fk_dml_type	dml_type,
		Foreign_key_chain *	chain
	)

static

Check all foreign key constraints on child tables for DML operation on a parent table.

Parameters

thd	Thread handle.
table_p	TABLE instance of a parent table.
dml_type	DML operation type.
chain	Foreign key chain.

Returns: true On error.; false On Success.

◆ check_all_parent_fk_ref()

bool check_all_parent_fk_ref	(	THD *	thd,
		const TABLE *	table_c,
		enum_fk_dml_type	dml_type
	)

Check all foreign key constraints on parent tables for DML operation on a child table.

Parameters

thd	Thread handle.
table_c	TABLE instance of a child table.
dml_type	DML operation type.

Returns: true On error.; false On Success.

◆ check_and_acquire_MDL_lock()

static bool check_and_acquire_MDL_lock	(	THD *	thd,
		const char *	db_name,
		const char *	table_name,
		enum_mdl_type	mdl_type
	)

static

Check if MDL lock is already acquired on the table.

If not, then acquire MDL lock on the schema and table.

Parameters

thd	Thread Handle.
db_name	DB name.
table_name	Table name.
mdl_type	MDL lock type.

Returns: true On error.; false On success.

◆ check_child_fk_ref()

static bool check_child_fk_ref	(	THD *	thd,
		const TABLE *	table_p,
		TABLE *	table_c,
		TABLE_SHARE_FOREIGN_KEY_INFO *	fk_c,
		enum_fk_dml_type	dml_type,
		Foreign_key_chain *	chain
	)

static

Checks foreign key constraint on child table.

Parameters

thd	Thread Handle.
table_p	TABLE instance of a parent table.
table_c	TABLE instance of a child table.
fk_c	Foreign key information.
dml_type	DML operation type.
chain	Foreign key chain.

Returns: true On error.; false On success.

◆ check_parent_fk_ref()

static bool check_parent_fk_ref	(	THD *	thd,
		const TABLE *	table_c,
		TABLE *	table_p,
		TABLE_SHARE_FOREIGN_KEY_INFO *	fk,
		enum_fk_dml_type	dml_type
	)

static

◆ find_fk_table_from_open_tables()

static TABLE * find_fk_table_from_open_tables	(	THD *	thd,
		const char *	db_name,
		const char *	table_name,
		const char *	fk_name
	)

static

Find TABLE instance of a foreign key table from the THD::open_tables list.

Parameters

thd	Thread Handle.
db_name	DB name.
table_name	Table name.
fk_name	Foreign key name.

Returns: TABLE* TABLE instance if found, otherwise nullptr.

◆ get_foreign_key_table()

static bool get_foreign_key_table	(	THD *	thd,
		const char *	db_name,
		const char *	table_name,
		const char *	fk_name,
		enum_fk_dml_type	dml_type,
		bool	open_table,
		TABLE **	table,
		bool *	table_exists,
		bool *	is_table_opened
	)

static

Function to get TABLE instance of a other table in FK relationship.

Table is first searched in the open table list. If table is not opened or scan is already opened, then table is opened.

Parameters

	thd	Thread Handle.
	db_name	DB name.
	table_name	Table name.
	fk_name	Foreign key name. If lock is not acquired, then MDL is acquired before opening the table.
	dml_type	DML operation type. If lock is not acquired, then MDL is acquired before opening the table.
	open_table	Do not search table in open_tables list, instead open table always.
[out]	table	TABLE instance.
[out]	table_exists	Flag is set to true, if table does not exists.
[out]	is_table_opened	Flag is set to true, if a table is opened.

Returns: true On error.; false On success.

◆ get_key_index()

static uint get_key_index	(	const TABLE *	table,
		uint	num_columns,
		LEX_CSTRING *	col_names
	)

static

Function to get index of key matching col_names in keys list.

Parameters

table	TABLE instance.
num_columns	Number of columns.
col_names	List of column names.

Returns: index of key in keys list on success, UINT_MAX if key not found.

◆ is_cascade_from_parent_legal()

bool is_cascade_from_parent_legal	(	const TABLE *	table_p,
		const KEY *	key_info_p,
		const KEY *	key_info_c
	)

Determine whether a cascaded update from the current state of the parent table record's foreign keys to the corresponding child table's foreign keys is legal.

An example of an illegal cascade is when a parent table foreign key column is a VARCHAR with a corresponding child foreign key CHAR column AND the length of the value in the parent column exceeds the number of characters allowed in the child column.

Parameters

table_p	parent table from which to check cascade.
key_info_p	descriptor of the foreign key index in the parent table.
key_info_c	descriptor of the foreign key index in the child table.

Return values

true	if the cascaded update is legal, false if the cascaded update is not legal.

◆ is_column_updated()

static bool is_column_updated	(	const TABLE *	table,
		uint	num_key_cols,
		LEX_CSTRING *	col_names
	)

static

Function to check if any of the foreign key columns updated.

Parameters

table	TABLE instance for a table.
num_key_cols	Number of columns.
col_names	List of columns.

Returns: true If any column is updated.; false If columns are not updated.

◆ is_fk_cascade()

static bool is_fk_cascade	(	TABLE *	table,
		enum_fk_dml_type	dml_type,
		const char *	fk_name
	)

static

Function to check if CASCADE action is defined for a foreign key on UPDATE or DELETE operations.

Parameters

table	TABLE instance of a table.
dml_type	DML operation type.
fk_name	Foreign key information.

Returns: true If CASCADE action for a DML operation is set.; false Otherwise.

◆ is_foreign_key_table_opened()

bool is_foreign_key_table_opened	(	THD *	thd,
		const char *	db_name,
		const char *	table_name,
		const char *	fk_name
	)

Check if TABLE instance for foreign key is already opened.

Parameters

thd	Thread handle.
db_name	DB name.
table_name	Table name.
fk_name	Foreign key name.

Returns: true If table for foreign key is already opened.; false If table is not opened.

◆ is_self_fk_value_same()

static bool is_self_fk_value_same	(	const TABLE *	table_c,
		TABLE_SHARE_FOREIGN_KEY_INFO *	fk
	)

static

Function to check value of foreign key columns and parent columns are same in case self referencing foreign key.

Parameters

table_c	TABLE instance of a table.
fk	Foreign key information.

Returns: true If values are same.; false otherwise.

◆ on_delete_cascade()

static bool on_delete_cascade	(	THD *	thd,
		TABLE *	table_c,
		TABLE_SHARE_FOREIGN_KEY_INFO *	fk_c,
		enum_fk_dml_type	dml_type,
		uchar *	key_value,
		int	key_len,
		Foreign_key_chain *	chain,
		int *	error
	)

static

Helper function to apply ON DELETE CASCADE to child table on DML operation.

Parameters

	thd	Thread Handle.
	table_c	TABLE instance of a child table.
	fk_c	Foreign key information.
	dml_type	DML operation type.
	key_value	Key value buffer.
	key_len	Length of key value buffer.
	chain	Foreign key chain.
[out]	error	Error value.

Returns: true On error.; false On success.

◆ on_delete_on_update_restrict_or_no_action()

static bool on_delete_on_update_restrict_or_no_action	(	THD *	thd,
		const TABLE *	table_c,
		TABLE_SHARE_FOREIGN_KEY_INFO *	fk_c,
		enum_fk_dml_type	dml_type
	)

static

Helper function to apply ON DELETE/ON UPDATE RESTRICT or NOACTION to child table on DML operation.

Note: ON DELETE|UPDATE SET DEFAULT also behaves like RESTRICT

Parameters

thd	Thread Handle.
table_c	TABLE instance of a child table.
fk_c	Foreign key information.
dml_type	DML operation type.

Returns: true On error.; false On success.

◆ on_delete_on_update_set_null()

static bool on_delete_on_update_set_null	(	THD *	thd,
		const TABLE *	table_p,
		TABLE *	table_c,
		TABLE_SHARE_FOREIGN_KEY_INFO *	fk_c,
		enum_fk_dml_type	dml_type,
		uchar *	key_value,
		int	key_len,
		Foreign_key_chain *	chain,
		int *	error
	)

static

Helper function to apply ON DELETE/ON UPDATE SET NULL to child table on DML operation.

Parameters

	thd	Thread Handle.
	table_p	TABLE instance of a parent table.
	table_c	TABLE instance of a child table.
	fk_c	Foreign key information.
	dml_type	DML operation type.
	key_value	Key value buffer.
	key_len	Length of key value buffer.
	chain	Foreign key chain.
[out]	error	Error value.

Returns: true On error.; false On success.

◆ on_update_cascade()

static bool on_update_cascade	(	THD *	thd,
		const TABLE *	table_p,
		TABLE *	table_c,
		TABLE_SHARE_FOREIGN_KEY_INFO *	fk_c,
		KEY *	key_info_p,
		uint	parent_key_idx,
		KEY *	key_info_c,
		uint	child_key_idx,
		enum_fk_dml_type	dml_type,
		uchar *	key_value,
		int	key_len,
		Foreign_key_chain *	chain,
		int *	error
	)

static

Function to apply ON UPDATE CASCADE to child table on DML operation.

Parameters

	thd	Thread Handle.
	table_p	TABLE instance of a parent table.
	table_c	TABLE instance of a child table.
	fk_c	Foreign key information.
	dml_type	DML operation type.
	key_info_p	Parent table key information.
	parent_key_idx	Parent table key index.
	key_info_c	Child table key information.
	child_key_idx	Child table key index.
	key_value	Key value buffer.
	key_len	Length of key value buffer.
	chain	Foreign key chain.
[out]	error	Error value.

Returns: true On error.; false On success.

◆ open_table_for_fk()

static TABLE * open_table_for_fk	(	THD *	thd,
		const char *	db_name,
		const char *	table_name
	)

static

Function to open table for foreign key validation.

Parameters

thd	Thread Handle.
db_name	DB name.
table_name	Table name.

Returns: TABLE* TABLE instance on success, nullptr otherwise.

◆ report_no_referenced_row_error()

static bool report_no_referenced_row_error	(	THD *	thd,
		const TABLE *	table_c,
		TABLE_SHARE_FOREIGN_KEY_INFO *	fk
	)

inlinestatic

Reports ER_NO_REFERENCED_ROW_2 error with fk information.

Parameters

thd	Thread Handle.
table_c	TABLE handle
fk	Foreign Key Information

Returns: true Propagates error

◆ report_row_referenced_error()

static bool report_row_referenced_error	(	THD *	thd,
		const TABLE *	table_c,
		TABLE_SHARE_FOREIGN_KEY_INFO *	fk
	)

inlinestatic

Reports ER_ROW_IS_REFERENCED_2 error with fk information.

Parameters

thd	Thread Handle.
table_c	TABLE handle
fk	Foreign Key Information

Returns: true Propagates error

◆ set_key_value_null()

static bool set_key_value_null	(	TABLE *	table,
		uint	num_key_cols,
		LEX_CSTRING *	col_names
	)

static

Function to set the null value for key columns.

Parameters

table	TABLE instance of a table.
num_key_cols	Number of columns.
col_names	List of columns.

Returns: false On Success.; true On failure.

◆ set_updated_key_value()

static bool set_updated_key_value	(	THD *	thd,
		TABLE *	table_c,
		int	child_key_idx,
		const TABLE *	table_p,
		int	parent_key_idx,
		TABLE_SHARE_FOREIGN_KEY_INFO *	fk
	)

static

Function to copy value to child table columns during UPDATE CASCADE operation.

Parameters

thd	Thread Handle.
table_c	TABLE instance of a child table.
child_key_idx	Index of key in the child table.
table_p	TABLE instance of a parent table.
parent_key_idx	Index of key in the parent table.
fk	Foreign key information.

Returns: false On Success.; true On failure.

◆ skip_foreign_key_checks()

static bool skip_foreign_key_checks	(	THD *	thd,
		const TABLE *	table
	)

static

Helper function to skip foreign checks.

Parameters

thd	Thread Handle.
table	TABLE instance of a table.

Returns: true If foreign key check for a table should be skipped.; false Otherwise.

Variable Documentation

◆ FK_MAX_CASCADE_DEPTH

constexpr uint32_t FK_MAX_CASCADE_DEPTH = 15

constexpr

With the ON CASCADE DELETE/UPDATE clause, deleting from the parent table can trigger recursive cascading calls.

This defines the maximum number of such cascading deletes or updates allowed. If this limit is exceeded, the delete operation on the parent table will fail, and the user must drop the excessive foreign key constraint before proceeding.

Classes

Functions

Variables

Function Documentation

◆ build_fk_error_message()

◆ check_all_child_fk_ref() [1/2]

◆ check_all_child_fk_ref() [2/2]

◆ check_all_parent_fk_ref()

◆ check_and_acquire_MDL_lock()

◆ check_child_fk_ref()

◆ check_parent_fk_ref()

◆ find_fk_table_from_open_tables()

◆ get_foreign_key_table()

◆ get_key_index()

◆ is_cascade_from_parent_legal()

◆ is_column_updated()

◆ is_fk_cascade()

◆ is_foreign_key_table_opened()

◆ is_self_fk_value_same()

◆ on_delete_cascade()

◆ on_delete_on_update_restrict_or_no_action()

◆ on_delete_on_update_set_null()

◆ on_update_cascade()

◆ open_table_for_fk()

◆ report_no_referenced_row_error()

◆ report_row_referenced_error()

◆ set_key_value_null()

◆ set_updated_key_value()

◆ skip_foreign_key_checks()

Variable Documentation

◆ FK_MAX_CASCADE_DEPTH