Hi Ed, Cool, I guess we both read/interpreted his post differently and gave two valid answers ;)
- Drew On Mar 30, 2011, at 5:40 PM, Ed Anuff wrote: > Hey Drew, I'm somewhat familiar with Snowflake, and it's certainly a > good option, but, my impression was that the main reason to use it is > because you find the 128-bits for a UUID overkill, not because it's > doing anything you can't do with UUID's. The difference in time > resolution between UUIDs and Snowflake ids is actually greater than > the size of the sequence value that Snowflake uses to differentiate > duplicated timestamps, so the easiest thing would be just to round to > milliseconds unless your goal was to save the extra 64 bits per UUID. > I was just over-reading into Roshan's question that he wanted the full > time resolution of a UUID and on top of that be able to have a number > of duplicate timestamps. > > On Wed, Mar 30, 2011 at 4:24 PM, Drew Kutcharian <d...@venarc.com> wrote: >> Hi Ed, >> >> There's no need to re-invent the wheel that's pretty much what Twitter >> Snowflake does. The way it works is it creates a 64 bit long id which is >> formatted as such >> >> time_bits : data_center_id : machine_id : sequence >> >> Where time_bits are the milliseconds since a custom epoch. >> >> So If you see, you would get ids that are unique and ordered by time up to >> 1ms (if two ids were created during the same millisecond, then the ordering >> is not preserved) >> >> - Drew >> >> >> On Mar 30, 2011, at 4:13 PM, Ed Anuff wrote: >> >>> If I understand the question, it's not that >>> UUIDGen.makeType1UUIDFromHost(InetAddress.getLocalHost()) is returning >>> duplicate UUID's. It should always be giving unique time-based uuids >>> and has checks to make sure it does. The question was whether it was >>> possible to get multiple unique time-based UUID's with the exact same >>> timestamp component, rather than avoiding duplicates in the timestamp >>> the way UUIDGen currently does. The answer to that is that you could >>> take a look at the code for the UUIDGen class and create your own >>> version that perhaps generated the clock sequence in a different way, >>> such as leaving a certain number of low order bits of the clock >>> sequence empty and then incrementing those when duplicate timestamps >>> were generated rather than incrementing the timestamp the way UUIDGen >>> currently does. >>> >>> On Wed, Mar 30, 2011 at 10:08 AM, Drew Kutcharian <d...@venarc.com> wrote: >>>> Hi Roshan, >>>> You probably want to look at Twitter's >>>> Snowflake: https://github.com/twitter/snowflake >>>> There's also another Java variant: https://github.com/earnstone/eid >>>> - Drew >>>> >>>> On Mar 30, 2011, at 6:08 AM, Roshan Dawrani wrote: >>>> >>>> Hi, >>>> Is there any way I can get multiple unique time UUIDs for the same >>>> timestamp >>>> value - I mean, the UUIDs that are same in their time (most significant >>>> bits), but differ in their least significant bits? >>>> The least significant bits added by >>>> me.prettyprint.cassandra.utils.TimeUUIDUtils seem to be a fixed value based >>>> on mac/ip address, which makes sure that I get the same UUID for a >>>> timestamp >>>> value, everytime I ask. >>>> I need the "(timestamp): <some value>" kind of columns that need to be >>>> sorted by time, and I wanted to use TimeUUID to use column sorting that >>>> comes out-of-the-box, but the problem is that I can get multiple values for >>>> the same timestamp. >>>> So, I am looking for some way where the time portion is same, but the other >>>> UUID half is different so that I can safely store "1 time UUID: 1 value". >>>> Any help there is appreciated. >>>> -- >>>> Roshan >>>> Blog: http://roshandawrani.wordpress.com/ >>>> Twitter: @roshandawrani >>>> Skype: roshandawrani >>>> >>>> >>>> >> >>
