Thanks for your help, David.
On Mon, Apr 5, 2010 at 7:25 PM, Andriy Bohdan <a.boh...@gmail.com> wrote:
> It makes sense.
>
> Thanks, David!
>
> On Mon, Apr 5, 2010 at 2:34 PM, David Timothy Strauss
> <da...@fourkitchens.com> wrote:
> > Cache the <product, tag> => <score> map as you write values (a
> "write-through" cache) so that reading the current score hits something like
> memcached instead of Cassandra. With a cache hit, you get an ideal,
> write-only path in Cassandra. Three blind writes in Cassandra is cheap -- no
> matter what your scale. The only risk is inability to efficiently remove old
> scores if you lose the contents of memcached, but that risk can be mitigated
> various ways.
> >
> > Of course, I'm assuming a single data center, here. Memcached isn't too
> useful for this if you need to update scores at two data centers.
> >
> > I'm not sure how much the 0.6 row cache might help in this case, too.
> >
> > ----- "Andriy Bohdan" <a.boh...@gmail.com> wrote:
> >
> >> Hello guys
> >>
> >> I have a pretty similar task. There's a need to store tags of
> >> products
> >> with score. Score may go up and down and tags have to be ordered by
> >> their score for each product. Score is updated "very" often.
> >>
> >> I was thinking of using the following model (simplified here for
> >> clarity):
> >>
> >> Product = {
> >> product_key: {
> >> name: ....
> >> etc..
> >> }
> >> ...
> >> }
> >>
> >> Product_Tags = {
> >> product_key : {
> >> tag_name: score
> >> ...
> >> }
> >> ...
> >> }
> >>
> >> Product_Tags_Ordered (compareWith:BytesType) = {
> >> product_key: {
> >> (score, time_uuid) : tag_name
> >> ...
> >> }
> >> ...
> >> }
> >>
> >> So to update a score of a tag:
> >> 1) need to look old value of score to be able to remove it from
> >> Product_Tags_Ordered
> >> 2) remove Row from Product_Tags_Ordered with old score
> >> 3) update score in Product_Tags
> >> 4) insert new Row into Product_Tags_Ordered with new score
> >>
> >> 4 IO operations look like a bit too much to update one score as for
> >> me.
> >>
> >> I'm curious if there's any better solution I missed.
> >>
> >>
> >> On Mon, Apr 5, 2010 at 11:54 AM, JKnight JKnight <beukni...@gmail.com>
> >> wrote:
> >> > Thanks David,
> >> > But what's does "monotonicity" mean?
> >> >
> >> > User's score belongs to their action. When they win the game or
> >> sale
> >> > something, user's score will increase. When user lose the game or
> >> buy
> >> > something, user's score will decrease.
> >> >
> >> > On Mon, Apr 5, 2010 at 4:09 AM, David Strauss
> >> <da...@fourkitchens.com>
> >> > wrote:
> >> >>
> >> >> I need the question about monotonicity answered, too.
> >> >>
> >> >> You should also know: Cassandra is not ideal for directly tracking
> >> >> values you increment or decrement.
> >> >>
> >> >> On 2010-04-05 08:04, JKnight JKnight wrote:
> >> >> > Thanks for for reply, David.
> >> >> >
> >> >> > I will tell more the detail about the system. My system is used
> >> to store
> >> >> > the score (point) user earn when they play game.
> >> >> >
> >> >> > "Mark" is the score.
> >> >> > User's score changes when user win game, buy or sell anything.
> >> >> >
> >> >> > Sorry I make a mistake. My data model is:
> >> >> >
> >> >> > Mark{ //Column Family
> >> >> > gameId:{ //row key
> >> >> > mark_userId: ""// (column name : value),
> >> >> > mark2_userId2: ""
> >> >> > },
> >> >> > gameId2:{//row key
> >> >> > mark_userId: ""
> >> >> > }
> >> >> > }
> >> >> >
> >> >> >
> >> >> > On Sun, Apr 4, 2010 at 11:44 PM, David Strauss
> >> <da...@fourkitchens.com
> >> >> > <mailto:da...@fourkitchens.com>> wrote:
> >> >> >
> >> >> > On 2010-04-05 02:48, JKnight JKnight wrote:
> >> >> > > I want to design the data storage to store user's mark for
> >> a large
> >> >> > > amount of user. When system run, user's mark changes
> >> frequently.
> >> >> >
> >> >> > What is a "mark"?
> >> >> >
> >> >> > > I want to list top 10 user have largest mark.
> >> >> >
> >> >> > Do the "marks" increase monotonically? What other properties
> >> do they
> >> >> > have?
> >> >> >
> >> >> > > Could we use Cassandra for store this data?
> >> >> > >
> >> >> > > Ex, here my Cassandra data model design:
> >> >> > > Mark{
> >> >> > > userId{
> >> >> > > mark_userId
> >> >> > > },
> >> >> > > }
> >> >> >
> >> >> > I do not understand that notation. What parts are the CF,
> >> key/row,
> >> >> > and
> >> >> > column?
> >> >> >
> >> >> > > When user's mark changes, we remove old mark_userId and add
> >> new
> >> >> > > mark_userId.
> >> >> > > Because user's mark change frequently and with large amount
> >> of
> >> >> > user, I
> >> >> > > think Cassandra can not satisfy.
> >> >> >
> >> >> > On the contrary, Cassandra excels at tracking rapidly
> >> changing data
> >> >> > and
> >> >> > even shards rows to scale I/O horizontally.
> >> >> >
> >> >> > --
> >> >> > David Strauss
> >> >> > | da...@fourkitchens.com <mailto:da...@fourkitchens.com>
> >> >> > Four Kitchens
> >> >> > | http://fourkitchens.com
> >> >> > | +1 512 454 6659 [office]
> >> >> > | +1 512 870 8453 [direct]
> >> >> >
> >> >> >
> >> >> >
> >> >> >
> >> >> > --
> >> >> > Best regards,
> >> >> > JKnight
> >> >>
> >> >>
> >> >> --
> >> >> David Strauss
> >> >> | da...@fourkitchens.com
> >> >> | +1 512 577 5827 [mobile]
> >> >> Four Kitchens
> >> >> | http://fourkitchens.com
> >> >> | +1 512 454 6659 [office]
> >> >> | +1 512 870 8453 [direct]
> >> >>
> >> >
> >> >
> >> >
> >> > --
> >> > Best regards,
> >> > JKnight
> >> >
> >>
> >>
> >>
> >> --
> >> Andriy
> >
> > --
> > David Strauss
> > | da...@fourkitchens.com
> > | +1 512 577 5827 [mobile]
> > Four Kitchens
> > | http://fourkitchens.com
> > | +1 512 454 6659 [office]
> > | +1 512 870 8453 [direct]
> >
>
>
>
> --
> Andriy
>
--
Best regards,
JKnight
