[Developers] timestamp uniqueness

[Kurt Bollacker]

On Fri, Apr 17, 2009 at 12:24:37PM -0700, augusto callejas wrote:
> another way i could ask my question is
> what guarantee is there for links that have
> the same timestamp up to the millisecond?

You'll notice that there are 4 digits after the second, not three.
Also, it is my understanding that these four digits represent a "write
serial number" within that second.  If it was 1/10 of a millisecond
indicator, you'd see an almost random distribution of values, but in
reality, you only see low numbers.  I don't know what happens if more
than 10,000 writes per second to Freebase were to occur.

								Kurt :-)




 
> empirically, i have seen two types:
> 
> 1) the update of a unique property that results in a delete link  
> followed by an insert link.
> 2) insert of a new node that results in a series of insert links
> 
> 
> On Apr 17, 2009, at 12:11 PM, augusto callejas wrote:
> 
> > hi-
> >
> > i've noticed when a unique property is updated,
> > that a delete occurs followed immediately by an
> > insert, with timestamp value +.0001.  (this insures
> > the same timestamp up to the millisecond value)
> >
> > my question is if another unique property is
> > immediately updated afterwards, will its
> > delete/insert links have a unique timestamp
> > up to the millisecond value compared to the
> > previous timestamp?
> >
> > that is, would i expect link timestamps like:
> >
> > 2008-08-20T05:27:45.0000Z delete
> > 2008-08-20T05:27:45.0001Z insert
> > 2008-08-20T05:27:45.0010Z delete
> > 2008-08-20T05:27:45.0011Z insert
> >
> > first two delete/insert have same timestamp up to the millisecond  
> > value,
> > while last two delete/isnert have same timestamp up to the millisecond
> > value.
> >
> > or could i see:
> >
> > 2008-08-20T05:27:45.0000Z delete
> > 2008-08-20T05:27:45.0001Z insert
> > 2008-08-20T05:27:45.0002Z delete
> > 2008-08-20T05:27:45.0003Z insert
> >
> > all delete/inserts have the same timestamp up to the millisecond  
> > value.
> >
> >   {
> >     "master_property" : "/business/company/founded",
> >     "operation" : "delete",
> >     "source" : {
> >       "guid" : "#9202a8c04000641f8000000005f43a01"
> >     },
> >     "target_value" : {
> >       "value" : "2006-08"
> >     },
> >     "timestamp" : "2008-08-20T05:27:45.0000Z",
> >     "type" : "/type/link",
> >     "valid" : null
> >   },
> >   {
> >     "master_property" : "/business/company/founded",
> >     "operation" : "insert",
> >     "source" : {
> >       "guid" : "#9202a8c04000641f8000000005f43a01"
> >     },
> >     "target_value" : {
> >       "value" : "2007-08"
> >     },
> >     "timestamp" : "2008-08-20T05:27:45.0001Z",
> >     "type" : "/type/link",
> >     "valid" : true
> >   }
> >
> > thanks,
> > augusto.
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> > Developers at freebase.com
> > http://lists.freebase.com/mailman/listinfo/developers
> 
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