11/24/2023 0 Comments Mysql add column data constraintIt seems that online DDL also available in MariaDBĪlternatively you can use ALTER ONLINE TABLE to ensure that your ALTER See MySQL 5.6 Reference Manual -> InnoDB and Online DDL for more info. Performing changes in-place where possible, rather than creating a new copy of the table, avoids temporary increases in disk space usage and I/O overhead associated with copying the table and reconstructing secondary indexes. When you omit the LOCK clause or specify LOCK=DEFAULT, MySQL allows as much concurrency as possible depending on the type of operation. It lets you adjust the balance between performance and concurrency during the DDL operation, by choosing whether to block access to the table entirely (LOCK=EXCLUSIVE clause), allow queries but not DML (LOCK=SHARED clause), or allow full query and DML access to the table (LOCK=NONE clause). Usage is controlled by the innodb_online_alter_log_max_size Table copy, or using a specially optimized type of table copy. The operation might be able to be performed without doing a The table can be modified concurrently while the ALTER TABLE is in The details vary according to the type of operation. Section 14.11, “InnoDB and Online DDL” for details. Of InnoDB tables during DDL (primarily ALTER TABLE) operations. Now MySQL offers a solution:Ī feature that improves the performance, concurrency, and availability This really is like an UPDATE on the Whole table, but with more impact.You're actually changing the physical structure on the disk, every record moves.Field Locks would be much harder than Row locks, never mind table locks.Adding a new field is like changing one field on every row.So I thought I'd put a new perspective on it to show why it's how it is. Some comments have been made about this limitation being a bit poor. The execution plans will likely no longer be valid. Once finished, recompile any stored procedures, etc that use that table. Once finished, change the name of the source table, then change the name of the new table. Although this would cause a slow down, it's not a lock.) Whilst always being cautious of any INSERT/UPDATE/DELETE on the source table. You can then copy the contents of the old table over a chunk at a time. The only other option is to do manually what many RDBMS systems do anyway.
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