Before commit 6112853cda in MySQL 4.1.1
introduced the parameter innodb_file_per_table, all InnoDB data was
written to the InnoDB system tablespace (often named ibdata1).
A serious design problem is that once the system tablespace has grown to
some size, it cannot shrink even if the data inside it has been deleted.
There are also other design problems, such as the server hang MDEV-29930
that should only be possible when using innodb_file_per_table=0 and
innodb_undo_tablespaces=0 (storing both tables and undo logs in the
InnoDB system tablespace).
The parameter innodb_change_buffering was deprecated
in commit b5852ffbee.
Starting with commit baf276e6d4
(MDEV-19229) the number of innodb_undo_tablespaces can be increased,
so that the undo logs can be moved out of the system tablespace
of an existing installation.
If all these things (tables, undo logs, and the change buffer) are
removed from the InnoDB system tablespace, the only variable-size
data structure inside it is the InnoDB data dictionary.
DDL operations on .ibd files was optimized in
commit 86dc7b4d4c (MDEV-24626).
That should have removed any thinkable performance advantage of
using innodb_file_per_table=0.
Since there should be no benefit of setting innodb_file_per_table=0,
the parameter should be deprecated. Starting with MySQL 5.6 and
MariaDB Server 10.0, the default value is innodb_file_per_table=1.
The MDEV-20265 commit e746f451d5
introduces DBUG_ASSERT(right_op == r_tbl) in
st_select_lex::add_cross_joined_table(), and that assertion would
fail in several tests that exercise joins. That commit was skipped
in this merge, and a separate fix of MDEV-20265 will be necessary in 10.4.
ha_innobase::open(): Always ignore problems with FOREIGN KEY constraints
(pass DICT_ERR_IGNORE_FK_NOKEY), no matter whether foreign_key_checks
is enabled. Instead, we must report errors when enforcing the FOREIGN KEY
constraints. As a result of ignoring these errors, the tables will be
loaded with dict_foreign_t objects whose foreign_index or referenced_index
will be NULL.
Also, pass DICT_ERR_IGNORE_FK_NOKEY instead of DICT_ERR_IGNORE_NONE
to dict_table_open_on_id_low() in many other cases. Notably, on
CREATE TABLE and ALTER TABLE, we will keep validating the FOREIGN KEY
constraints as before.
dict_table_open_on_name(): If no other flags than
DICT_ERR_IGNORE_FK_NOKEY are set, refuse access to unreadable tables.
Some encryption tests rely on this code path.
For the DML code path, we used to have the problem that when
one of the indexes was missing in dict_foreign_t, we would ignore
the FOREIGN KEY constraint altogether. The following changes
address that.
row_ins_check_foreign_constraints(): Add the parameter pk.
For the primary key, consider also foreign key constraints for which
foreign->foreign_index=NULL (no underlying index is available).
row_ins_check_foreign_constraint(): Report errors also for !check_ref.
Remove a redundant check for srv_read_only_mode.
row_ins_foreign_report_add_err(): Tolerate foreign->foreign_index=NULL.
