How Can I Perform MySQL ALTER TABLE Operations Without Locking the Table?

Performing ALTER TABLE Without Locking the Table in MySQL

ALTER TABLE statements typically acquire a read lock on the entire table during their execution, preventing concurrent write operations. This can cause significant performance impacts for large tables. Fortunately, alternative methods exist to avoid table locking during ALTER TABLE operations.

One approach is to manually perform the necessary operations without using the ALTER TABLE statement. This involves creating a new table with the desired column structure, copying the data from the existing table in chunks while managing potential concurrent changes, and finally renaming the tables to swap their roles. While this method is time-consuming and error-prone, it allows for continuous updates to the table during the process.

To understand why traditional ALTER TABLE operations acquire locks, it's important to recognize that adding a new field resembles modifying every row in the table. Field-level locks are impractical, and physical file structures change as records are rearranged to accommodate the new field. Effectively, it's a comprehensive table-wide update with substantial impact.

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