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mariadb/sql/partition_element.h
Mattias Jonsson f693203e80 Bug#14521864: MYSQL 5.1 TO 5.5 BUGS PARTITIONING 
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;
2013-01-30 17:51:52 +01:00

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#ifndef PARTITION_ELEMENT_INCLUDED
#define PARTITION_ELEMENT_INCLUDED
/* Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
#include "my_base.h" /* ha_rows */
#include "handler.h" /* UNDEF_NODEGROUP */
/**
* An enum and a struct to handle partitioning and subpartitioning.
*/
enum partition_type {
NOT_A_PARTITION= 0,
RANGE_PARTITION,
HASH_PARTITION,
LIST_PARTITION
};
enum partition_state {
PART_NORMAL= 0,
PART_IS_DROPPED= 1,
PART_TO_BE_DROPPED= 2,
PART_TO_BE_ADDED= 3,
PART_TO_BE_REORGED= 4,
PART_REORGED_DROPPED= 5,
PART_CHANGED= 6,
PART_IS_CHANGED= 7,
PART_IS_ADDED= 8,
PART_ADMIN= 9
};
/*
This struct is used to keep track of column expressions as part
of the COLUMNS concept in conjunction with RANGE and LIST partitioning.
The value can be either of MINVALUE, MAXVALUE and an expression that
must be constant and evaluate to the same type as the column it
represents.
The data in this fixed in two steps. The parser will only fill in whether
it is a max_value or provide an expression. Filling in
column_value, part_info, partition_id, null_value is done by the
function fix_column_value_function. However the item tree needs
fixed also before writing it into the frm file (in add_column_list_values).
To distinguish between those two variants, fixed= 1 after the
fixing in add_column_list_values and fixed= 2 otherwise. This is
since the fixing in add_column_list_values isn't a complete fixing.
*/
typedef struct p_column_list_val
{
void* column_value;
Item* item_expression;
partition_info *part_info;
uint partition_id;
bool max_value;
bool null_value;
char fixed;
} part_column_list_val;
/*
This struct is used to contain the value of an element
in the VALUES IN struct. It needs to keep knowledge of
whether it is a signed/unsigned value and whether it is
NULL or not.
*/
typedef struct p_elem_val
{
longlong value;
uint added_items;
bool null_value;
bool unsigned_flag;
part_column_list_val *col_val_array;
} part_elem_value;
struct st_ddl_log_memory_entry;
class partition_element :public Sql_alloc {
public:
List<partition_element> subpartitions;
List<part_elem_value> list_val_list;
ha_rows part_max_rows;
ha_rows part_min_rows;
longlong range_value;
char *partition_name;
char *tablespace_name;
struct st_ddl_log_memory_entry *log_entry;
char* part_comment;
char* data_file_name;
char* index_file_name;
handlerton *engine_type;
enum partition_state part_state;
uint16 nodegroup_id;
bool has_null_value;
bool signed_flag; // Range value signed
bool max_value; // MAXVALUE range
partition_element()
: part_max_rows(0), part_min_rows(0), range_value(0),
partition_name(NULL), tablespace_name(NULL),
log_entry(NULL), part_comment(NULL),
data_file_name(NULL), index_file_name(NULL),
engine_type(NULL), part_state(PART_NORMAL),
nodegroup_id(UNDEF_NODEGROUP), has_null_value(FALSE),
signed_flag(FALSE), max_value(FALSE)
{
}
partition_element(partition_element *part_elem)
: part_max_rows(part_elem->part_max_rows),
part_min_rows(part_elem->part_min_rows),
range_value(0), partition_name(NULL),
tablespace_name(part_elem->tablespace_name),
part_comment(part_elem->part_comment),
data_file_name(part_elem->data_file_name),
index_file_name(part_elem->index_file_name),
engine_type(part_elem->engine_type),
part_state(part_elem->part_state),
nodegroup_id(part_elem->nodegroup_id),
has_null_value(FALSE)
{
}
~partition_element() {}
};
#endif /* PARTITION_ELEMENT_INCLUDED */
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