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Displaying posts with tag: Atomic DDL (reset)
Sep
22
2026
How Atomic DDL Works in MySQL 8.0
Posted by Libing Song on Tue 22 Sep 2026 02:00 UTC
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Before MySQL 8.0, DDL was not crash-safe. There were three main problems:

  1. The metadata in the server layer and the metadata/data in InnoDB could become inconsistent.

    The server-layer metadata was stored in files — for example, table definitions were kept in .frm files — while InnoDB kept its own copy of the metadata in its tables. A crash could leave the server-layer metadata inconsistent with InnoDB’s metadata or even with the table data. For example, the server layer still had the table’s .frm file and believed the table existed, but InnoDB’s .ibd data file was gone, so InnoDB believed the table did not exist.

  2. InnoDB’s metadata and data could become inconsistent.

  3. The binlog and the data could become inconsistent.

    For example, after a crash and …

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