Jan Walraven
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  • Posted on November 23, 2021

    To list all tables with locks, run the following SQL query:

    show open tables where `In_use` > 1

    Fields:

    1. Database – The database containing the table.
    2. Table – The table name.
    3. In_use – The number of table locks or lock requests there are for the table. For example, if one client acquires a lock for a table using LOCK TABLE t1 WRITE, In_use is 1. If another client issues LOCK TABLE t1 WRITE while the table remains locked, the client blocks waiting for the lock, but the lock request causes In_use to be 2. If the count is zero, the table is open but not currently being used. In_use is also increased by the HANDLER … OPEN statement and decreased by HANDLER … CLOSE.
    4. Name_locked – Whether the table name is locked. Name locking is used for operations such as dropping or renaming tables.
    More info about open tables can be found here.