MDEV-20865 Store foreign key info in TABLE_SHARE
1. Access foreign keys via TABLE_SHARE::foreign_keys and
TABLE_SHARE::referenced_keys;
foreign_keys and referenced_keys are objects in TABLE_SHARE.
2. Remove handler FK interface:
- get_foreign_key_list()
- get_parent_foreign_key_list()
- referenced_by_foreign_key()
3. Invalidate referenced shares on:
- RENAME TABLE
- DROP TABLE
- RENAME COLUMN
- ADD FOREIGN KEY
When foreign table is created or altered by the above operations all
referenced shares are closed. This blocks the operation while any
referenced shares are used (when at least one its TABLE instance is
locked).
4. Update referenced shares on:
- CREATE TABLE
On CREATE TABLE add items to referenced_keys of referenced shares.
5. Invalidate foreign shares on:
- RENAME TABLE
- RENAME COLUMN
The above-mentioned blocking takes effect.
6. Check foreign/referenced shares consistency on:
- CHECK TABLE
7. Temporary change until MDEV-21051:
InnoDB fill foreign key info at handler open().
On first TABLE open FK info is loaded from storage engine into
TABLE_SHARE. All referenced shares (if any exist) are closed. This
leads to blocking of first time foreign table open while referenced
tables are used.
Restore states of referenced shares in case of errors.
FOREIGN_KEY_INFO refactored to FK_info holding Lex_cstring
(MDEV-21311) Converge Foreign_key and supplemental generated Key together
mysql_prepare_create_table() does data validation and such utilities
as automatic name generation. But it does that only for indexes and
ignores Foreign_key objects. Now as Foreign_key data needs to be
stored in FRM files as well this processing must be done for them like
for any other Key objects.
Replace Key::FOREIGN_KEY type with Key::foreign flag of type
Key::MULTIPLE and Key::generated set to true. Construct one object
with Key::foreign == true instead of two objects of type
Key::FOREIGN_KEY and Key::MULTIPLE.
(MDEV-21051) datadict refactorings
- Move read_extra2() to datadict.cc
- Refactored extra2_fields to Extra2_info
- build_frm_image() readability
(MDEV-21051) build_table_shadow_filename() refactoring
mysql_prepare_alter_table() leaks fixes
(MDEV-21051) amend system tables locking restriction
Table mysql.help_relation has foreign key to mysql.help_keyword. On
bootstrap when help_relation is opened, it preopens help_keyword for
READ and fails in lock_tables_check().
If system table is opened for write then fk references are opened for
write.
Related to: Bug#25422, WL#3984
Tests: main.lock
(MDEV-21051) Store and read foreign key info into/from FRM files
1. Introduce Foreign_key_io class which creates/parses binary stream
containing foreign key structures. Referenced tables store there only
hints about foreign tables (their db and name), they restore full info
from the corresponding tables.
Foreign_key_io is stored under new EXTRA2_FOREIGN_KEY_INFO field in
extra2 section of FRM file.
2. Modify mysql_prepare_create_table() to generate names for foreign
keys. Until InnoDB storage of foreign keys is removed, FK names must
be unique across the database: the FK name must be based on table
name.
3. Keep stored data in sync on DDL changes. Referenced tables update
their foreign hints after following operations on foreign tables:
- RENAME TABLE
- DROP TABLE
- CREATE TABLE
- ADD FOREIGN KEY
- DROP FOREIGN KEY
Foreign tables update their foreign info after following operations on
referenced tables:
- RENAME TABLE
- RENAME COLUMN
4. To achieve 3. there must be ability to rewrite extra2 section of
FRM file without full reparse. FRM binary is built from primary
structures like HA_CREATE_INFO and cannot be built from TABLE_SHARE.
Use shadow write and rename like fast_alter_partition_table()
does. Shadow FRM is new FRM file that replaces the old one.
Create table workflow:
1. Foreign_key is constructed in parser, placed into alter_info->key_list;
2. mysql_prepare_create_table() translates them to FK_info, assigns
foreign_id if needed;
3. build_frm_image() writes two FK_info lists into FRM's extra2
section, for referenced keys it stores only table names (hints);
4. init_from_binary_frm_image() parses extra2 section and fills
foreign_keys and referenced_keys of TABLE_SHARE.
It restores referenced_keys by reading hint list of table names,
opening corresponding shares and restoring FK_info from their
foreign_keys. Hints resolution is done only when initializing
non-temporary shares. Usually temporary share has different
(temporary) name and it is impossible to resolve foreign keys by that
name (as we identify them by both foreign and referenced table
names). Another not unimportant reason is performance: this saves
spare share acquisitions.
Alter table workflow:
1. Foreign_key is constructed in parser, placed into
alter_info->key_list;
2. mysql_prepare_alter_table() prepares action lists and share list of
foreigns/references;
3. mysql_prepare_alter_table() locks list of foreigns/references by
MDL_INTENTION_EXCLUSIVE, acquires shares;
4. prepare_create_table() converts key_list into FK_list, assigns
foreign_id;
5. shadow FRM of altered table is created;
6. data is copied;
7. altered table is locked by MDL_EXCLUSIVE;
8. fk_handle_alter() processes action lists, creates FK backups,
modifies shares, writes shadow FRMs;
9. altered table is closed;
10. shadow FRMs are installed;
11. altered table is renamed, FRM backup deleted;
12. (TBD in MDEV-21053) shadow FRMs installation log closed, backups deleted;
On FK backup system:
In case of failed DDL operation all shares that was modified must be
restored into original state. This is done by FK_ddl_backup (CREATE,
DROP), FK_rename_backup (RENAME), FK_alter_backup (ALTER).
On STL usage:
STL is used for utility not performance-critical algorithms, core
structures hold native List. A wrapper was made to convert STL
exception into bool error status or NULL value.
MDEV-20865 fk_check_consistency() in CHECK TABLE
Self-refs fix
Test table_flags fix: "debug" deviation is now gone.
