CODEWITHSUNDEEP
mysqlsqlalter-table
Edy Bourne
Edy Bourne

Reputation: 6207

Add NULL column very large MySQL table - does it take much longer than adding to a small table?

Logic says it should be really fast to add a NULL column even if adding to a very large (~800 GB) table.

Obviously if the ALTER TABLE has a NOT NULL for the new column it will take a long time, but how about for NULL columns? How does it compare to altering a small table?

I'm on MySql 5.5.

Thanks!

Upvotes: 3

Views: 2617

Answers (1)

RandomSeed
RandomSeed

Reputation: 29769

MySQL implements ALTER TABLE as a table recreation.

In most cases, ALTER TABLE makes a temporary copy of the original table (...) incorporates the alteration into the copy, deletes the original table, and renames the new one.

The manual goes on and explains what "most cases" means. Basically: adding, removing, and redefining columns.

Only the table size matters, the column type has little to no impact in terms of execution time.

Upvotes: 4

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