I did not understand before... sorry.
Again, depending upon how many reminders you have for a single user, this could
be a long/wide row. Again, it really comes down to how many reminders are we
talking about and how often will they be read/written. While a single row can
contain millions (maybe more) columns, that doesn't mean it's a good idea.
I'm working on a logging system with Cassandra and ran into this same type of
problem. Do I put all of the messages for a single system into a single row
keyed off that system's name? I quickly came to the answer of "no" and now I
break my row keys into POSIX_timestamp:system where my timestamps are buckets
for every 5 minutes. This nicely distributes the load across the nodes in my system.
Bill-
On 02/02/2011 11:18 AM, Aditya Narayan wrote:
You got me wrong perhaps..
I am already splitting the row on per user basis ofcourse, otherwise
the schema wont make sense for my usage. The row contains only
*reminders of a single user* sorted in chronological order. The
reminder Id are stored as supercolumn name and subcolumn contain tags
for that reminder.
On Wed, Feb 2, 2011 at 9:19 PM, William R Speirs<bill.spe...@gmail.com> wrote:
Any time I see/hear "a single row containing all ..." I get nervous. That
single row is going to reside on a single node. That is potentially a lot of
load (don't know the system) for that single node. Why wouldn't you split it
by at least user? If it won't be a lot of load, then why are you using
Cassandra? This seems like something that could easily fit into an
SQL/relational style DB. If it's too much data (millions of users, 100s of
millions of reminders) for a standard SQL/relational model, then it's
probably too much for a single row.
I'm not familiar with the TTL functionality of Cassandra... sorry cannot
help/comment there, still learning :-)
Yea, my $0.02 is that this is an effective way to leverage super columns.
Bill-
On 02/02/2011 10:43 AM, Aditya Narayan wrote:
I think you got it exactly what I wanted to convey except for few
things I want to clarify:
I was thinking of a single row containing all reminders (& not split
by day). History of the reminders need to be maintained for some time.
After certain time (say 3 or 6 months) they may be deleted by ttl
facility.
"While presenting the reminders timeline to the user, latest
supercolumns like around 50 from the start_end will be picked up and
their subcolumns values will be compared to the Tags user has chosen
to see and, corresponding to the filtered subcolumn values(tags), the
rows of the reminder details would be picked up.."
Is supercolumn a preferable choice for this ? Can there be a better
schema than this ?
-Aditya Narayan
On Wed, Feb 2, 2011 at 8:54 PM, William R Speirs<bill.spe...@gmail.com>
wrote:
To reiterate, so I know we're both on the same page, your schema would be
something like this:
- A column family (as you describe) to store the details of a reminder.
One
reminder per row. The row key would be a TimeUUID.
- A super column family to store the reminders for each user, for each
day.
The row key would be something like: YYYYMMDD:user_id. The column names
would simply be the TimeUUID of the messages. The sub column names would
be
the tag names of the various reminders.
The idea is that you would then get a slice of each row for a user, for a
day, that would only contain sub column names with the tags you're
looking
for? Then based upon the column names returned, you'd look-up the
reminders.
That seems like a solid schema to me.
Bill-
On 02/02/2011 09:37 AM, Aditya Narayan wrote:
Actually, I am trying to use Cassandra to display to users on my
applicaiton, the list of all Reminders set by themselves for
themselves, on the application.
I need to store rows containing the timeline of daily Reminders put by
the users, for themselves, on application. The reminders need to be
presented to the user in a chronological order like a news feed.
Each reminder has got certain tags associated with it(so that, at
times, user may also choose to see the reminders filtered by tags in
chronological order).
So I thought of a schema something like this:-
-Each Reminder details may be stored as separate rows in column family.
-For presenting the timeline of reminders set by user to be presented
to the user, the timeline row of each user would contain the Id/Key(s)
(of the Reminder rows) as the supercolumn names and the subcolumns
inside that supercolumns could contain the list of tags associated
with particular reminder. All tags set at once during first write. The
no of tags(subcolumns) will be around 8 maximum.
Any comments, suggestions and feedback on the schema design are
requested..
Thanks
Aditya Narayan
On Wed, Feb 2, 2011 at 7:49 PM, Aditya Narayan<ady...@gmail.com>
wrote:
Hey all,
I need to store supercolumns each with around 8 subcolumns;
All the data for a supercolumn is written at once and all subcolumns
need to be retrieved together. The data in each subcolumn is not big,
it just contains keys to other rows.
Would it be preferred to have a supercolumn family or just a standard
column family containing "all the subcolumns data serialized in single
column(s) " ?
Thanks
Aditya Narayan
