phantom mnesia backup entries

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phantom mnesia backup entries

tom kelly
Hi list,

I've been examining an mnesia backup from one of our production machines using the traverse_backup function and have found some strange entries. In one fragmented set table (with no secondary indexes) where the record structure is meant to be {tab_name, key, field1, field2} there exist entries like: {tab_name, key}.
However I can't find the entries after loading the table fragment with mnesia:restore.

I've been trawling through our app to find where these might get created but have drawn a blank and have come to the provisional conclusion that they're an internal mnesia quirk.

Can any of the mnesia experts on the list confirm or deny? And if confirmed maybe provide a short explanation of their function to satisfy my curiosity?

Many thanks.

//TTom.


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Re: phantom mnesia backup entries

Dan Gudmundsson-2
From memory and without checking I believe those are delete markers for that record entry.



On Wed, Oct 1, 2014 at 2:25 PM, tom kelly <[hidden email]> wrote:
Hi list,

I've been examining an mnesia backup from one of our production machines using the traverse_backup function and have found some strange entries. In one fragmented set table (with no secondary indexes) where the record structure is meant to be {tab_name, key, field1, field2} there exist entries like: {tab_name, key}.
However I can't find the entries after loading the table fragment with mnesia:restore.

I've been trawling through our app to find where these might get created but have drawn a blank and have come to the provisional conclusion that they're an internal mnesia quirk.

Can any of the mnesia experts on the list confirm or deny? And if confirmed maybe provide a short explanation of their function to satisfy my curiosity?

Many thanks.

//TTom.


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Re: phantom mnesia backup entries

Håkan Mattsson
Yes, they are. They are typically inserted if the table is being updated during the backup. You will probably see the old record(s),  the delete marker and the new record(s) in the backup. In that order.

/Håkan

On Wed, Oct 1, 2014 at 8:18 PM, Dan Gudmundsson <[hidden email]> wrote:
From memory and without checking I believe those are delete markers for that record entry.



On Wed, Oct 1, 2014 at 2:25 PM, tom kelly <[hidden email]> wrote:
Hi list,

I've been examining an mnesia backup from one of our production machines using the traverse_backup function and have found some strange entries. In one fragmented set table (with no secondary indexes) where the record structure is meant to be {tab_name, key, field1, field2} there exist entries like: {tab_name, key}.
However I can't find the entries after loading the table fragment with mnesia:restore.

I've been trawling through our app to find where these might get created but have drawn a blank and have come to the provisional conclusion that they're an internal mnesia quirk.

Can any of the mnesia experts on the list confirm or deny? And if confirmed maybe provide a short explanation of their function to satisfy my curiosity?

Many thanks.

//TTom.


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[hidden email]
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