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Date: Thu, 29 Dec 2011 15:12:08 -0500
Message-ID: 
 <CAENxBwwnpvJNXG-DE6vQiMv9w2_jyeH0vc3Cm-qt17b1HH6qvQ@mail.gmail.com>
Subject: Re: Retrieve all composite columns from a row, whose composite name's
 first component matches from a list of Integers
From: Edward Capriolo <edlinuxguru@gmail.com>
To: user@cassandra.apache.org
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

Hum...

Do you have this?
scf [b][1][a]=3Dvalue
scf [b][1][x]=3Dvalue
scf [b][7][b]=3Dvalue

and you want to slice:
scf [b][1][*]

Which would result in

scf [b][1][a]=3Dvalue
scf [b][1][x]=3Dvalue

?

The composite version of this would be:
cf [b][1:a]=3Dvalue
cf [b][1:x]=3Dvalue
cf [b][7:b]=3Dvalue

I am not sure exactly what you are doing because A SlicePredicate
takes either a list of columns or a SliceRange. A ColumnPath takes a
Single SuperColumn.

I do not see how this is done with Columns or SuperColumns. Maybe you
can provide a code snippet and/or some sample data?

On 12/29/11, Aditya <adynnn@gmail.com> wrote:
> @Edward: Perhaps you missed to notice that I need to always retrieve 'all
> columns' under the supercolumn at any time.. and as per my query
> requirements if I use composite columns instead of supercolumns then it i=
s
> impossible to do wildcard queries like the ones asked in this thread's
> headline but which is much easier to do through the use of supercolumns.
>
> On Thu, Dec 29, 2011 at 11:06 PM, Edward Capriolo
> <edlinuxguru@gmail.com>wrote:
>
>> The use case in question was: Only accessing some columns.
>>
>> Even if that is not the case:
>>
>> SuperColumns: 1 extra level of nesting
>> Composite Colunns: Arbitrary levels of nesting
>>
>> SuperColumns: More overhead (space on disk) then using your own delimite=
r
>> '_'
>> SuperColumns: Likely going to be replaced in future c* version behind
>> the scenes by composite columns anyway
>> SuperColumns: Usually an afterthought for API developers, (support for
>> them comes "later")
>> SuperColumns: Almost always utilized incorrectly by users, users speak
>> of '10%' performance gains after they switch away from them.
>>
>> There are some (a small % of cases) where SuperColumns are a better
>> choice, but this is rare. With composites and concatenating columns
>> they have no great purpose any more, (bad analogy coming!) like a
>> mechanical type writer.
>>
>> On 12/29/11, Philippe <watcherfr@gmail.com> wrote:
>> > Would you stand by that statement in case all colums inside the super
>> > column need to be read?  Why?
>> >
>> > Thanks
>> > Le 28 d=E9c. 2011 19:26, "Edward Capriolo" <edlinuxguru@gmail.com> a
>> =E9crit :
>> >
>> >> Super columns have the same fundamental problem and perform worse in
>> >> general. So switching from composites to super columns is NEVER a goo=
d
>> >> idea.
>> >>
>> >>
>> >> On Wed, Dec 28, 2011 at 1:19 PM, Aditya <adynnn@gmail.com> wrote:
>> >>
>> >>> Since I have around 20 items to query, I guess making 20 queries to
>> >>> retrieve activities by all followies on all of those 20 columns woul=
d
>> too
>> >>> inefficient, so to take the advantage of more efficient queries, are
>> >>> supercolumns recommended for this case ? Anyways, in case I use
>> >>> supercolumns, I need to retrieve the entire supercolumn at any point
>> >>> of
>> >>> time & I am writing subcolumn(s) to the supercolumn at different tim=
es
>> >>> not
>> >>> at once.
>> >>>
>> >>> On Wed, Dec 28, 2011 at 8:07 PM, Edward Capriolo
>> >>> <edlinuxguru@gmail.com>wrote:
>> >>>
>> >>>> You need to execute one get slice operation for each item id or if
>> >>>> the
>> >>>> row is not large , you can try one large get slice on the entire ro=
w
>> and
>> >>>> deal with the results client side.
>> >>>>
>> >>>> If you try method 1 When doing slices on composites you can set the
>> >>>> start inclusive or exclusive values to get only the column you want
>> and
>> >>>> not
>> >>>> some extra columns up to slice range size.
>> >>>>
>> >>>>
>> >>>> On Tuesday, December 27, 2011, Aditya <adynnn@gmail.com> wrote:
>> >>>> > I need to store data of all activities by user's followies in
>> >>>> > single
>> >>>> row. I am trying to do that making use of composite column names in=
 a
>> >>>> single user specific row named 'rowX'.
>> >>>> > On any activity by a user's followie on an item, a column is stor=
ed
>> in
>> >>>> 'rowX'. The column has a composite type column name made up of
>> >>>> itemId+userId (which makes it unique col. name) in rowX. (& column
>> value
>> >>>> contains the activity data related to that item by that followie)
>> >>>> >
>> >>>> > Now I want to retrieve activity by all users on a list of items. =
So
>> I
>> >>>> need to retrieve all composite columns with composite's first
>> component
>> >>>> matching the itemId. Is it possible to do such a query to Cassandra=
 ?
>> I
>> >>>> am
>> >>>> using Hector.
>> >>>>
>> >>>
>> >>>
>> >>
>> >
>>
>