Shulou(Shulou.com)05/31 Report--

This article mainly explains "what is the working process of pt-online-schema-chang". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn "how pt-online-schema-chang works."

Pt-online-schema-change is a member of Percona-toolkit. By improving the native ddl, the table structure can be modified online without locking the table.

The working process is as follows:

1. Create a new empty table structure that is the same as the table to perform the alter operation (the structure before alter)

two。 Execute alter table statements in the new table (should be fast)

3. Create triggers in the original table. Three triggers correspond to insert,update,delete operations.

4. Copy data from the original table to the temporary table with a fixed block size, and all writes to the original table through the trigger on the original table will be updated to the new temporary table during the copying process.

5.Rename original table to old table, in the temporary table Rename as the original table

6. If there is a foreign key referring to the table, detect the table related to the foreign key according to the value of the alter-foreign-keys-method parameter, and do the corresponding setting processing.

7. Finally, delete the old table and the triggers on the original table.

At this point, I believe you have a deeper understanding of "how pt-online-schema-chang works". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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