i would respectfully disagree, what you have said is true but it really
depends on the use case.
1) do you expect to be doing updates to individual fields of an item, or
will you always update all fields at once? if you are doing separate
updates then the first is definitely easier to handle updates.
2) do you expect to do paging of the list? this will be easier with the
json approach, as in the first your item may span across a page boundary
- not an insurmountable problem by any means, but more complicated
nonetheless. this is not
an issue obviously if all your items have the same number of fields.
3) do you expect to read or delete multiple items individually? you may
have to do multiple reads/deletes of a row if the items are not adjacent
to each other as you cannot do 'disjoint' slices of columns at the
moment. with the json approach you can just specify individual columns
and you're done. again this is less of an issue if items have a known
set of fields, but your list of columns to read/delete may get quite
large fairly quickly
the first is definitely better if you want to update individual fields,
read-then-write is not a good idea in cassandra. but it is more
complicated for most usage scenarios, so you have to work out if you
really need the extra flexibility.
On 24/08/2012 13:54, samal wrote:
First is better choice, each filed can be updated separately(write only).
Second you have to take care json yourself (read first-modify-then write).
On Fri, Aug 24, 2012 at 5:45 PM, Roshni Rajagopal
<roshni.rajago...@wal-mart.com <mailto:roshni.rajago...@wal-mart.com>>
wrote:
Hi,
Suppose I have a column family to associate a user to a dynamic
list of items. I want to store 5-10 key information about the
item, & no specific sorting requirements are there.
I have two options
A) use composite columns
UserId1 : {
<itemid1>:<Name> = Betty Crocker,
<itemid1>:<Descr> = Cake
<itemid1>:<Qty> = 5
<itemid2>:<Name> = Nutella,
<itemid2>:<Descr> = Choc spread
<itemid2>:<Qty> = 15
}
B) use a json with the data
UserId1 : {
<itemid1> = {name: Betty Crocker,descr: Cake, Qty: 5},
<itemid2> ={name: Nutella,descr: Choc spread, Qty: 15}
}
Which do you suggest would be better?
Regards,
Roshni
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