MySQL/MariaDB – Get Partition Name from Value

mariadbMySQLmysql-5.7

I have my table partitioned on day of month basis.

Now I need to archive data of the last 16th day date_add(now(), interval -16 day) to another table. For that I need to find out the partition name that contains data of the date, so that I can exchange the partition and export to another table.

But my problem is,I don't know how to find the partition name from value, "I need to exchange and archive.

Your help will be highly appreciated.

Thanks

Best Answer

information_schema.PARTITIONS.PARTITION_DESCRIPTION

Consider naming the partitions in an obvious way, such as

p20200419

to contain data for the 19th (and defined LESS THAN ('2020-04-20'))

More tips: http://mysql.rjweb.org/doc.php/partitionmaint and its companion: http://mysql.rjweb.org/demo_part_maint.pl.txt

Example

Given:

SHOW CREATE TABLE pmdemo.pmdemo\G
*************************** 1. row ***************************
       Table: pmdemo
Create Table: CREATE TABLE `pmdemo` (
  `dt` datetime NOT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
/*!50100 PARTITION BY RANGE (TO_DAYS(dt))
(PARTITION `start` VALUES LESS THAN (0) ENGINE = MyISAM,
 PARTITION from20121008 VALUES LESS THAN (735150) ENGINE = MyISAM,
 PARTITION from20121009 VALUES LESS THAN (735151) ENGINE = MyISAM,
 PARTITION from20121010 VALUES LESS THAN (735152) ENGINE = MyISAM,
 PARTITION from20121011 VALUES LESS THAN (735153) ENGINE = MyISAM,
 PARTITION future VALUES LESS THAN MAXVALUE ENGINE = MyISAM) */
1 row in set (0.01 sec)

This select:

mysql> SELECT * FROM information_schema.`PARTITIONS`
      WHERE table_name = 'pmdemo'
        AND partition_description = TO_DAYS('2012-10-10')\G

*************************** 1. row ***************************
                TABLE_CATALOG: def
                 TABLE_SCHEMA: pmdemo
                   TABLE_NAME: pmdemo
               PARTITION_NAME: from20121009  -- the partition name
            SUBPARTITION_NAME: NULL
   PARTITION_ORDINAL_POSITION: 3
SUBPARTITION_ORDINAL_POSITION: NULL
             PARTITION_METHOD: RANGE
          SUBPARTITION_METHOD: NULL
         PARTITION_EXPRESSION: TO_DAYS(ft) -- a convenient formula for time-series
      SUBPARTITION_EXPRESSION: NULL
        PARTITION_DESCRIPTION: 735151  -- the TO_DAYS() in the query
                   TABLE_ROWS: 0
               AVG_ROW_LENGTH: 0
                  DATA_LENGTH: 0
              MAX_DATA_LENGTH: 1970324836974591
                 INDEX_LENGTH: 1024
                    DATA_FREE: 0
                  CREATE_TIME: 2017-01-09 13:49:01
                  UPDATE_TIME: 2017-01-09 13:49:01
                   CHECK_TIME: NULL
                     CHECKSUM: NULL
            PARTITION_COMMENT: 
                    NODEGROUP: default
              TABLESPACE_NAME: NULL
1 row in set (0.00 sec)

Related Solutions

Mysql – How to improve the SQL statement with weekly results with week starting on Thursday or any other day of the week

Here is a query I wrote up to give you the most recent thursday and the ending wednesday

SELECT thuwk_beg + INTERVAL 0 second thu_beg,
thuwk_beg + INTERVAL 604799 second wed_end
FROM (SELECT (DATE(NOW()) - INTERVAL daysbacktothursday DAY) thuwk_beg
FROM (SELECT SUBSTR('3456012',wkndx,1) daysbacktothursday
FROM (SELECT DAYOFWEEK(dt) wkndx FROM (SELECT DATE(NOW()) dt) AAAA) AAA) AA) A;

Here is an example for today, 2011-09-21

mysql> SELECT
    -> thuwk_beg + INTERVAL 0 second thu_beg,
    -> thuwk_beg + INTERVAL 604799 second wed_end
    -> FROM (SELECT (DATE(NOW()) - INTERVAL daysbacktothursday DAY) thuwk_beg
    -> FROM (SELECT SUBSTR('3456012',wkndx,1) daysbacktothursday
    -> FROM (SELECT DAYOFWEEK(dt) wkndx FROM (SELECT DATE(NOW()) dt) AAAA) AAA) AA) A;
+---------------------+---------------------+
| thu_beg             | wed_end             |
+---------------------+---------------------+
| 2011-09-15 00:00:00 | 2011-09-21 23:59:59 |
+---------------------+---------------------+
1 row in set (0.00 sec)

Just replace the NOW() function calls with whatever datetime you like and you will have the week starting Thursday all the time for the give datetime you choose.

Here is another example using the specific date '2011-01-01'

mysql> SELECT
    -> thuwk_beg + INTERVAL 0 second thu_beg,
    -> thuwk_beg + INTERVAL 604799 second wed_end
    -> FROM (SELECT (DATE('2011-01-01') - INTERVAL daysbacktothursday DAY) thuwk_beg
    -> FROM (SELECT SUBSTR('3456012',wkndx,1) daysbacktothursday
    -> FROM (SELECT DAYOFWEEK(dt) wkndx FROM (SELECT DATE('2011-01-01') dt) AAAA) AAA) AA) A;
+---------------------+---------------------+
| thu_beg             | wed_end             |
+---------------------+---------------------+
| 2010-12-30 00:00:00 | 2011-01-05 23:59:59 |
+---------------------+---------------------+
1 row in set (0.00 sec)

Your query of table referencing today would resemble something like this:

SELECT * from `table`,
(SELECT thuwk_beg + INTERVAL 0 second thu_beg,
thuwk_beg + INTERVAL 604799 second wed_end
FROM (SELECT (DATE(NOW()) - INTERVAL daysbacktothursday DAY) thuwk_beg
FROM (SELECT SUBSTR('3456012',wkndx,1) daysbacktothursday
FROM (SELECT DAYOFWEEK(dt) wkndx FROM (SELECT DATE(NOW()) dt) AAAA) AAA) AA) A) M
WHERE `date` >= thu_beg
AND `date` <= wed_end;

Give it a Try !!!

UPDATE 2011-09-22 16:27 EDT

This was my proposed query for marking Thu-Wed.

SELECT thuwk_beg + INTERVAL 0 second thu_beg,
thuwk_beg + INTERVAL 604799 second wed_end
FROM (SELECT (DATE(NOW()) - INTERVAL daysbacktothursday DAY) thuwk_beg
FROM (SELECT SUBSTR('3456012',wkndx,1) daysbacktothursday
FROM (SELECT DAYOFWEEK(dt) wkndx FROM (SELECT DATE(NOW()) dt) AAAA) AAA) AA) A;

How about other weeks ???

(SELECT SUBSTR('6012345',wkndx,1) does the week starting Mon ending Sun
(SELECT SUBSTR('5601234',wkndx,1) does the week starting Tue ending Mon
(SELECT SUBSTR('4560123',wkndx,1) does the week starting Wed ending Tue
(SELECT SUBSTR('3456012',wkndx,1) does the week starting Thu ending Wed
(SELECT SUBSTR('2345601',wkndx,1) does the week starting Fri ending Thu
(SELECT SUBSTR('1234560',wkndx,1) does the week starting Sat ending Fri
(SELECT SUBSTR('0123456',wkndx,1) does the week starting Sun ending Sat

Mysql – How to partition a table by timestamp, where data from every i’th day goes to partition i

You can't use FROM_UNIXTIME() because hash partitions must be based on an integer expression. But assuming your timestamp is stored as an integer, you can use DIV to return an integer.

Here's a demo of partitioning in the way you describe:

mysql> create table table_to_partition (
  my_timestamp int unsigned primary key
) partition by hash(my_timestamp DIV (60*60*24)) partitions 3;

mysql> insert into table_to_partition values (unix_timestamp(now()));
mysql> insert into table_to_partition values (unix_timestamp(now()-interval 1 day));
mysql> insert into table_to_partition values (unix_timestamp(now()-interval 2 day));
mysql> insert into table_to_partition values (unix_timestamp(now()-interval 3 day));
mysql> insert into table_to_partition values (unix_timestamp(now()-interval 4 day));
mysql> insert into table_to_partition values (unix_timestamp(now()-interval 5 day));

mysql> select table_name, partition_name, table_rows 
from information_schema.partitions where table_name='table_to_partition';

+--------------------+----------------+------------+
| table_name         | partition_name | table_rows |
+--------------------+----------------+------------+
| table_to_partition | p0             |          2 |
| table_to_partition | p1             |          2 |
| table_to_partition | p2             |          2 |
+--------------------+----------------+------------+

Best Answer

Related Solutions

Mysql – How to improve the SQL statement with weekly results with week starting on Thursday or any other day of the week

Mysql – How to partition a table by timestamp, where data from every i’th day goes to partition i

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