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  1. MariaDB Server
  2. MDEV-39548

Cleanup MDL_request boilerplate

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      MDL improvements were made internally changing a backup lock from MDL_request to MDL_ticket and removed lock instance on the stack.

      Reloading ACLs (FLUSH PRIVILEGES) was decoupled from this backup lock.

      Improvement thanks to Long Jin of AWS
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      MDL improvements were made internally changing a backup lock from MDL_request to MDL_ticket and removed lock instance on the stack. Reloading ACLs (FLUSH PRIVILEGES) was decoupled from this backup lock. Improvement thanks to Long Jin of AWS

    Description

      Currently typical MDL lock acquisition is as follows:

      MDL_request mdl_request;
      		 
      MDL_REQUEST_INIT(&mdl_request, namespace, db, object, lock_type, duration);
      		 
      if (mdl_context.acquire_lock(&mdl_request, lock_wait_timeout))
      		 
        /* error handling */;
      		 
      ticket= mdl_request.ticket;

      This should be replaced with:

      if (!(ticket= mdl_context.ACQUIRE_LOCK(namespace, db, object, lock_type, lock_wait_timeout)))
      		 
        /* error handling */;

      This will significantly lower MDL_request exposure and should reduce likelihood of bugs like MDEV-39241. This is a step towards making MDL_request a private class of MDL, such that issues like MDEV-39184 will not pop up again.

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          relates to

          Task - A task that needs to be done. MDEV-39184 Rework MDL enum constants values

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-39241 THD::backup_commit_lock warning dangling-pointer

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Stalled

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              svoj Sergey Vojtovich
              svoj Sergey Vojtovich
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                Updated:
                Resolved:

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