The InnoDB internal tables SYS_TABLESPACES and SYS_DATAFILES as well as the
INFORMATION_SCHEMA views INNODB_SYS_TABLESPACES and INNODB_SYS_DATAFILES
were introduced in MySQL 5.6 for no good reason in
mysql/mysql-server/commit/e9255a22ef16d612a8076bc0b34002bc5a784627
when the InnoDB support for the DATA DIRECTORY attribute was introduced.
The file system should be the authoritative source of information on files.
Storing information about file system paths in the file system (symlinks,
or even the .isl files that were unfortunately chosen as the solution) is
sufficient. If information is additionally stored in some hidden tables
inside the InnoDB system tablespace, everything unnecessarily becomes
more complicated, because more copies of data mean more opportunity
for the copies to be out of sync, and because modifying the data in
the system tablespace in the desired way might not be possible at all
without modifying the InnoDB source code. So, the copy in the system
tablespace basically is a redundant, non-authoritative source of
information.
We will stop creating or accessing the system tables SYS_TABLESPACES
and SYS_DATAFILES.
We will also remove the view
INFORMATION_SCHEMA.INNODB_SYS_DATAFILES along with SYS_DATAFILES.
The view
INFORMATION_SCHEMA.INNODB_SYS_TABLESPACES will be repurposed
to directly reflect fil_system.space_list. The column
PAGE_SIZE, which would always contain the value of
the GLOBAL read-only variable innodb_page_size, is
removed. The column ZIP_PAGE_SIZE, which would actually
contain the physical page size of a page, is renamed to
PAGE_SIZE. Finally, a new column FILENAME is added, as a
replacement of SYS_DATAFILES.PATH.
This will also
address MDEV-21801 (files that were created before upgrading
to MySQL 5.6 or MariaDB 10.0 or later were never registered
in SYS_TABLESPACES or SYS_DATAFILES) and
MDEV-21801 (information about the system tablespace is not stored
in SYS_TABLESPACES or SYS_DATAFILES).
MySQL 5.7 allows temporary tables to be created in ROW_FORMAT=COMPRESSED.
The usefulness of this is questionable. WL#7899 in MySQL 8.0.0
prevents the creation of such compressed tables, so that all InnoDB
temporary tables will be located inside the predefined
InnoDB temporary tablespace.
Pick up and adjust some tests from MySQL 5.7 and 8.0.
dict_tf_to_fsp_flags(): Remove the parameter is_temp.
fsp_flags_init(): Remove the parameter is_temporary.
row_mysql_drop_temp_tables(): Remove. There cannot be any temporary
tables in InnoDB. (This never removed #sql* tables in the datadir
which were created by DDL.)
dict_table_t::dir_path_of_temp_table: Remove.
create_table_info_t::m_temp_path: Remove.
create_table_info_t::create_options_are_invalid(): Do not allow
ROW_FORMAT=COMPRESSED or KEY_BLOCK_SIZE for temporary tables.
create_table_info_t::innobase_table_flags(): Do not unnecessarily
prevent CREATE TEMPORARY TABLE with SPATIAL INDEX.
(MySQL 5.7 does allow this.)
fil_space_belongs_in_lru(): The only FIL_TYPE_TEMPORARY tablespace
is never subjected to closing least-recently-used files.
