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Re: [Bacula-devel] small dbcheck patch for mysql

2008/9/9 Bill Moran <wmoran@xxxxxxxxxxxxxxxxxxxxxxx>:
> In response to Dan Langille <dan@xxxxxxxxxxxx>:
> The canonical way to solve this would be to keep a reference counter in
> the filename/path tables that keeps track of how many file entries
> reference that row.  When it's hits 0, it can be deleted.  But this
> creates other issues:
> 1) What is the overhead of maintaining the reference counter?
> 2) In the case of a crash, we _must_ fix all reference counters immediately,
>   otherwise records could be deleted that still need to be used.

This is a canonical path for file systems, but not for DBMS. Imho.
It will require an additional fields, or new tables.
Productivity should be reduced.
"reference counter" will be an excess additional dependence, because
it can be computed from other addictions, available in the database.


And another note:
If have, for example in table Path, there is a orphaned record with
column Path(1) = "/path1/", and in carrying out the next Job meet
another Path(2) = "/path1/", then the first record Path(1) will cease
to be "orphaned".
I.e. DB would do "recovery" itself.
See also "Sequence of Creation of Records for a Save Job"

with best regards

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