[horde] Shortening Histories

[Michael J Rubinsky]

Quoting Jan Schneider <jan at horde.org>:

> Zitat von Ralf Lang <lang at b1-systems.de>:
>
>> Over the years, the Horde_Histories table can become quite large.  
>> It may make sense to sort out entries we won't need anymore
>>
>> * Entries for users or items which have disappeared, been deleted  
>> outside of horde or directly on the backend

On the contrary, I would argue we should technically do the opposite  
and create History entries for items that have been deleted outside of  
Horde or directly on the backend so that Horde can be made aware of  
it. In fact, this has come up recently on the ML, or maybe it was in  
an enhancement request. Of course doing so is no easy task.

>> * Changes so far past that we don't care anymore

I wouldn't object to some configuration that would allow the table to  
be trimmed after some configurable time (probably measured in years)  
but there would need to be a pretty loud warning on the configuration  
page that this could lead to changes being missed by sync clients.

>> If I read the code correctly, ActiveSync completely relies on its  
>> own tables and does not need very old history entries.
>>
>> The listBy code in Turba, Kronolith, Nag and Mnemo relies on  
>> histories to detect changes made at certain points or intervals in  
>> time

In fact, ActiveSync uses exactly these API methods (via the getChanges  
wrapper method).


>> Imp optionally writes a mail creation log but I don't know if  
>> anything consumes it.

It is a possible source for the results of IMP's favouriteRecipients  
API method.


>> Will anything break if I delete far-past histories? I'd use code,  
>> not bare DB statements.

As Jan mentioned, sync clients would not receive any changes if they  
have not yet synced the changes you delete. Additionally, IMP uses  
History to write the Maillog - which stores things like if/when a  
message was responded to etc... So if a message still exists and you  
remove those entries you loose this trail.

> I'm pretty sure ActiveSync still uses Horde_History, and DAV  
> definitely does. What you lose if you delete old entries, is that  
> users that haven't synced since then, but do after you deleted the  
> entry, won't get the changes.
>
> -- 
> Jan Schneider
> The Horde Project
> https://www.horde.org/
>
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-- 
mike
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