DOWNGRADED FROM 5.6.11 TO 5.6.10
Problem was new syntax not accepted by previous version.
Fixed by adding version comment of /*!50531 around the
new syntax.
Like this in the .frm file:
'PARTITION BY KEY /*!50611 ALGORITHM = 2 */ () PARTITIONS 3'
and also changing the output from SHOW CREATE TABLE to:
CREATE TABLE t1 (a INT)
/*!50100 PARTITION BY KEY */ /*!50611 ALGORITHM = 1 */ /*!50100 ()
PARTITIONS 3 */
It will always add the ALGORITHM into the .frm for KEY [sub]partitioned
tables, but for SHOW CREATE TABLE it will only add it in case it is the non
default ALGORITHM = 1.
Also notice that for 5.5, it will say /*!50531 instead of /*!50611, which
will make upgrade from 5.5 > 5.5.31 to 5.6 < 5.6.11 fail!
If one downgrades an fixed version to the same major version (5.5 or 5.6) the
bug 14521864 will be visible again, but unless the .frm is updated, it will
work again when upgrading again.
Also fixed so that the .frm does not get updated version
if a single partition check passes.
Due to an internal change in the server code in between 5.1 and 5.5
(wl#2649) the hash function used in KEY partitioning changed
for numeric and date/time columns (from binary hash calculation
to character based hash calculation).
Also enum/set changed from latin1 ci based hash calculation to
binary hash between 5.1 and 5.5. (bug#11759782).
These changes makes KEY [sub]partitioned tables on any of
the affected column types incompatible with 5.5 and above,
since the calculation of partition id differs.
Also since InnoDB asserts that a deleted row was previously
read (positioned), the server asserts on delete of a row that
is in the wrong partition.
The solution for this situation is:
1) The partitioning engine will check that delete/update will go to the
partition the row was read from and give an error otherwise, consisting
of the rows partitioning fields. This will avoid asserts in InnoDB and
also alert the user that there is a misplaced row. A detailed error
message will be given, including an entry to the error log consisting
of both table name, partition and row content (PK if exists, otherwise
all partitioning columns).
2) A new optional syntax for KEY () partitioning in 5.5 is allowed:
[SUB]PARTITION BY KEY [ALGORITHM = N] (list_of_cols)
Where N = 1 uses the same hashing as 5.1 (Numeric/date/time fields uses
binary hashing, ENUM/SET uses charset hashing) N = 2 uses the same
hashing as 5.5 (Numeric/date/time fields uses charset hashing,
ENUM/SET uses binary hashing). If not set on CREATE/ALTER it will
default to 2.
This new syntax should probably be ignored by NDB.
3) Since there is a demand for avoiding scanning through the full
table, during upgrade the ALTER TABLE t PARTITION BY ... command is
considered a no-op (only .frm change) if everything except ALGORITHM
is the same and ALGORITHM was not set before, which allows manually
upgrading such table by something like:
ALTER TABLE t PARTITION BY KEY ALGORITHM = 1 () or
ALTER TABLE t PARTITION BY KEY ALGORITHM = 2 ()
4) Enhanced partitioning with CHECK/REPAIR to also check for/repair
misplaced rows. (Also works for ALTER TABLE t CHECK/REPAIR PARTITION)
CHECK FOR UPGRADE:
If the .frm version is < 5.5.3
and uses KEY [sub]partitioning
and an affected column type
then it will fail with an message:
KEY () partitioning changed, please run:
ALTER TABLE `test`.`t1` PARTITION BY KEY ALGORITHM = 1 (a)
PARTITIONS 12
(i.e. current partitioning clause, with the addition of
ALGORITHM = 1)
CHECK without FOR UPGRADE:
if MEDIUM (default) or EXTENDED options are given:
Scan all rows and verify that it is in the correct partition.
Fail for the first misplaced row.
REPAIR:
if default or EXTENDED (i.e. not QUICK/USE_FRM):
Scan all rows and every misplaced row is moved into its correct
partitions.
5) Updated mysqlcheck (called by mysql_upgrade) to handle the
new output from CHECK FOR UPGRADE, to run the ALTER statement
instead of running REPAIR.
This will allow mysql_upgrade (or CHECK TABLE t FOR UPGRADE) to upgrade
a KEY [sub]partitioned table that has any affected field type
and a .frm version < 5.5.3 to ALGORITHM = 1 without rebuild.
Also notice that if the .frm has a version of >= 5.5.3 and ALGORITHM
is not set, it is not possible to know if it consists of rows from
5.1 or 5.5! In these cases I suggest that the user does:
(optional)
LOCK TABLE t WRITE;
SHOW CREATE TABLE t;
(verify that it has no ALGORITHM = N, and to be safe, I would suggest
backing up the .frm file, to be used if one need to change to another
ALGORITHM = N, without needing to rebuild/repair)
ALTER TABLE t <old partitioning clause, but with ALGORITHM = N>;
which should set the ALGORITHM to N (if the table has rows from
5.1 I would suggest N = 1, otherwise N = 2)
CHECK TABLE t;
(here one could use the backed up .frm instead and change to a new N
and run CHECK again and see if it passes)
and if there are misplaced rows:
REPAIR TABLE t;
(optional)
UNLOCK TABLES;
* rename all debugging related command-line options
and variables to start from "debug-", and made them all
OFF by default.
* replace "MySQL" with "MariaDB" in error messages
* "Cast ... converted ... integer to it's ... complement"
is now a note, not a warning
* @@query_cache_strip_comments now has a session scope,
not global.
Partitions can have different ref_length (position data length).
Removed DBUG_ASSERT which crashed debug builds when using
MAX_ROWS on some partitions.
