renaming a locked table

Question

When migrating a table to a new schema I want to make sure to have an atomic switch to the new table using the copy and rename procedure. Hence I am trying to rename a locked table like this:

CREATE TABLE foo_new (...)

-- copy data to new table, might take very long
INSERT INTO foo_new (id,created_at,modified_at)
  SELECT * FROM foo WHERE id <= 3;

LOCK TABLES foo WRITE, foo_new WRITE;

-- quickly copy the tiny rest over
INSERT INTO foo_new (id,created_at,modified_at)
  SELECT * FROM foo WHERE id > 3;

-- now switch to the new table
RENAME TABLE foo TO foo_old, foo_new TO foo;

UNLOCK TABLES;

Unfortunately that results in ERROR 1192 (HY000): Can't execute the given command because you have active locked tables or an active transaction.

How should this be done differently?

This is with mariadb:10.1.

Answer 1

While in general Rick is right to use the Percona Tools (see 1 and 2), the answer to the question really is to use ALTER TABLE. I thought RENAME was just an alias - but it seems like that's not the case.

Test seem to indicate that this works OK:

CREATE TABLE foo_new (...)

-- copy data to new table, might take very long
INSERT INTO foo_new (id,created_at,modified_at)
  SELECT * FROM foo WHERE id <= 3;

LOCK TABLES foo WRITE, foo_new WRITE;

-- quickly copy the tiny rest over
INSERT INTO foo_new (id,created_at,modified_at)
  SELECT * FROM foo WHERE id > 3;

-- now switch to the new table
ALTER TABLE foo RENAME TO foo_old;
ALTER TABLE foo_new RENAME TO foo;

UNLOCK TABLES;

Answer 2

You can do it like this:

CREATE TABLE foo_old (...)
LOCK TABLES foo WRITE; 
INSERT INTO foo_old (id,created_at,modified_at)
  SELECT * FROM foo;
DELETE FROM foo WHERE id <= 3;
UNLOCK TABLES;

As the error message states, you can't use RENAME TABLE while having the same table locked.