12/29/2023 0 Comments Mysql add column huge table![]() ![]() Reading and writing the table with no interruption. As you know, MySQL locks tablesįor most ALTER operations, but pt-online-Īny locking. You to ALTER large tables with no blocking orĭowntime. Pt-online-schema-change, a tool that enables Share Improve this answer Follow answered at 17:15 Nestor 13. b/c then the engine needs to create a new table and copy the data to the new table. What takes a long time is to insert columns in the middle of other columns. With this release we introduce a new version of ALTER TABLE table1 ADD newcolumn int NULL GO should not take that long. Percona created a toolkit which apparently works on all storage engines: If an index has all the data required by a query, it will never go to the actual table. We shall execute the following query to add id column to students table. Whenever you create an index, a copy of the indexed column + the primary key is created on disk, and the index is kept in memory as much as possible. Example 1 Add Column to MySQL Table In this example, we shall add a new column to the students table whose structure is given below: Now we shall add a new column, named id which shall be the PRIMARY key and AUTOINCREMENT for every new record. Tho, I can't promise this would all work safely on the MyISAM Engine Creating and maintaining an index on a huge table is costlier than on smaller tables. Query OK, 0 rows affected (0.01 sec) mysql> ALTER TABLE t2 ALTER COLUMN b SET. Facebook had to deal with this on a way higher level, check this out The ALTER TABLE statements add columns and change default column values. 'if it works' - because in some cases - i.e. This is by far the easiest and best approach if it works. adding columns (nullable) without locking tables. You'll have to replay the data delta after you're done. Modern databases (including MySQL) support online DDLs e.g. This way no table properties will be forgotten to. I suggest to create a copy, and alter the copy. You can right-click a table and select Send to SQL Editor -> Create Statement. On MySQL 5.5 (faster index creation, innodb), 8-core CPU, chip disks, altering a 5 mil row table with several indexes takes about 15-20 minutes in our case. Depending on factors like hardware, table structure and of course amount of rows (which you said is quite high) the alter will take a while. This doesn't mean that the server doesn't accept queries on other sessions while locked but they are queued up and probably time out before your ALTER TABLE is done. ![]() Table is locked while DDL queries are performed. ![]()
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