[Opensim-dev] Opensim database management - garbage collection

[J Ross Nicoll]

I realise they're epoch times, it just seems a little odd to have them  
instead of database native date/time types. I wondered if there was a  
compatibility reason or something...

Number of times accessed makes it easy to sweep for assets that were  
accessed once and then discarded, which is going to be by far the most  
common case for assets that can be deleted. It also I think provides a  
nice second level of safety that you're not about to delete something  
that was in heavy use until some point in time. Even for a table of 1  
million entries, we're talking about 4MB of data added. Heck, use a 16- 
bit integer, cap the count at 65536, it's only 2MB of data and still  
works for my main use case.

On 15 Jan 2009, at 17:24, Charles Krinke wrote:

> The integers for create_time and access_time are "epoch times",  
> where the beginning of the epoch is 1/1/70.
>
> To convert one uses the mysql function from_unixtime(create_time) or  
> from_unixtime(access_time) to see a YY-MM-DD-HH-MM-SS format.
>
> On OSGrid, we now have about 1,000,000 entries in the assets table  
> consuming about 50 GBytes. Of those 1,000,000 entries, about half  
> have create_time == 0. It looks like the earliest is around the  
> beginning of November, 2008 when the logic to write create_time and  
> access_time became operational.
>
> I look at that and think that have access_time and create_time is a  
> really good thing. I am not sure I could support number of times  
> accessed as these seem sufficient to me at this point, but perhaps I  
> am being myopic.
>
> Charles
>
> From: J Ross Nicoll <jrn2005 at cs.st-andrews.ac.uk>
> To: opensim-dev at lists.berlios.de
> Sent: Thursday, January 15, 2009 7:37:16 AM
> Subject: Re: [Opensim-dev] Opensim database management - garbage  
> collection
>
> Any chance of a number of times accessed field for assets, in addition
> to the access_time field?
>
> While I'm looking at the assets table, is there any specific reason
> why creation/access times are stored as integers rather than using
> actual date & time types?
>
> On 15 Jan 2009, at 00:24, Mike Mazur wrote:
>
> > Hi,
> >
> > On Wed, 14 Jan 2009 22:22:09 +0000
> > Ai Austin <ai.ai.austin at googlemail.com> wrote:
> >
> >> I wonder if someone can summarise for me the way in which Opensim
> >> manages old inaccessible assets...
> >
> > From what I understand, nothing is done to old inaccessible assets.
> > There is some difficulty in determining which assets are  
> inaccessible.
> > The reasons include:
> >
> > - assets can be referenced in scripts by UUID (so I heard)
> > - assets may be referenced by regions not currently online
> >
> > In a grid where you control all the regions and databases, it should
> > be
> > feasible to write a tool that can discover inaccessible assets.
> >
> >> I.e. if someone uploads a texture, perhaps uses
> >> it on an object that is then deleted, and then delete a texture, is
> >> it removed from the database... or can it persist and be there
> >> forever?
> >
> > AFAIK the texture remains in the DB forever.
> >
> > Mike
> > _______________________________________________
> > Opensim-dev mailing list
> > Opensim-dev at lists.berlios.de
> > https://lists.berlios.de/mailman/listinfo/opensim-dev
>
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