The root cause is the WAL logging of file operation when the actual
operation fails afterwards. It creates a situation with a log entry for
a operation that would always fail. I could simulate both the backup
scenario error and Innodb recovery failure exploiting the weakness.
We are following WAL for file rename operation and once logged the
operation must eventually complete successfully, or it is a major
catastrophe. Right now, we fail for rename and handle it as normal error
and it is the problem.
I created a patch to address RENAME operation to a non existing schema
where the destination schema directory is missing. The patch checks for
the missing schema before logging in an attempt to avoid the failure
after WAL log is written/flushed. I also checked that the schema cannot
be dropped or there cannot be any race with other rename to the same
file. This is protected by the MDL lock in SQL today.
The patch should this be a good improvement over the current situation
and solves the issue at hand.
after previous error upon multi-RENAME
- InnoDB fails to rename the foreign key constraint while
rollbacking the rename operation. In that case, InnoDB should
rename the FK constraint too.
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).
When attempting to rename a table to a non-existing database,
InnoDB would misleadingly report "OS error 71" when in fact the
error code is InnoDB's own (OS_FILE_NOT_FOUND), and not report
both pathnames. Errors on rename could occur due to reasons
connected to either pathname.
os_file_handle_rename_error(): New function, to report errors in
renaming files.
Cherry-pick the commit from MySQL 5.7.19, and adapt the test case:
commit 45c933ac19c73a3e9c756a87ee1ba18ba1ac564c
Author: Aakanksha Verma <aakanksha.verma@oracle.com>
Date: Tue Mar 21 10:31:43 2017 +0530
Bug #25189192 ERRORS WHEN RESTARTING MYSQL AFTER RENAME TABLE.
PROBLEM
While renaming table innodb doesn't update the InnoDB Dictionary table
INNODB_SYS_DATAFILES incase there is change in database while doing
rename table. Hence on a restart the server log shows error that it
couldnt find table with old path before rename which has actually been
renamed. So the errors would only vanish if we update the system
tablespace
FIX
Update the innodb dictionary table with new path in the case there is
not a change in the table but the database holding the table as well.
Reviewed-by: Jimmy Yang<Jimmy.Yang@oracle.com>
RB: 15751
