Contents
What does ALGORITHM INPLACE do?
When an operation on the primary key uses ALGORITHM=INPLACE , even though the data is still copied, it is more efficient than using ALGORITHM=COPY because: No undo logging or associated redo logging is required for ALGORITHM=INPLACE . These operations add overhead to DDL statements that use ALGORITHM=COPY .
What is MySQL ALGORITHM INPLACE?
ALTER TABLE in MySql allows ALGORITHM=INPLACE for avoiding table copy during altering. But for default they use copy instead of inplace.
Does ALTER table LOCK table MySQL?
Yes, it locks the table. From the docs on MySQL 8, The exception referred to earlier is that ALTER TABLE blocks reads (not just writes) at the point where it is ready to clear outdated table structures from the table and table definition caches. At this point, it must acquire an exclusive lock.
How can I make my alter table faster?
Just use ALTER TABLE as usual, it’ll be mostly instant for renames and index drops, and reasonably fast for index addition (as fast as reading all the table once). If using 5.1+, and the InnoDB plugin is enabled, adding/removing indices will be online as well.
Which is not a processing algorithm for database views?
A view algorithm can be UNDEFINED for three reasons: No ALGORITHM clause is present in the CREATE VIEW statement. The CREATE VIEW statement has an explicit ALGORITHM = UNDEFINED clause. ALGORITHM = MERGE is specified for a view that can be processed only with a temporary table.
What is alter table in MySQL?
The MySQL ALTER TABLE statement is used to add, modify, or drop/delete columns in a table. The MySQL ALTER TABLE statement is also used to rename a table.
Does a select lock a table?
Yes, select locks the table until reads completes which conflicts with Insert/Delete/Updates lock mode. Generally Select should be used with WITH (NOLOCK) to avoid blocking the dml operations but it will result in dirty reads. You will need to weigh between concurrency and data consistency.
Why does alter table take so long?
The schema change it taking so long because you are assigning a default value to the column during the change and enforcing that with a non-nullable column, and it has to populate the column for 60+ million rows, which is an incredibly expensive operation.