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Date: Thu, 13 Sep 2012 10:59:07 -0700
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 <CAA9Bfg-Vzca55Rw4cPQXK9JwY_u+ppm2HEO6MCgXS2eyP_pi4g@mail.gmail.com>
Subject: Re: Data Model
From: Soumya Acharya <cse.soumya@gmail.com>
To: user@cassandra.apache.org
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I just started learning Cassandra any suggestion where to start with ??


Thanks
Soumya

On Thu, Sep 13, 2012 at 10:54 AM, Roshni Rajagopal <
roshni_rajagopal@hotmail.com> wrote:

>  I want to learn how we can model a mix of static and dynamic columns in
> a family.
>
> Consider a course_students col family which gives a list of students for a
> course
> with row key- Course Id
> Columns - Name, Teach_Nm, StudID1, StudID2, StudID3
> Values - Maths, Prof. Abc, 20,21,25
> where 20,21,25 are IDs of students.
>
> We have
>
> fixed columns like Course Name, Teacher Name, and a dynamic number of
>
> columns like 'StudID1', 'StudID2' etc, and my thoughts were that we could
>
> look for 'StudID' and get all the columns with the student Ids in Hector.
> But the
>
> question was how would we determine the number for the column, like to add
>
> StudID3 we need to read the row and identify that 2 students are there,
>
> and this is the third one.
>
>
> So we can remove the number in the column name, altogether and keep
>
> columns like Course Name, Teacher Name, Student:20,Student:21, Student:25,
>
> where the second part is the actual student id. However here we run into
>
> the second issue that we cannot have some columns of a composite format
>
> and some of another format, when we use static column families- all
>
> columns would need to be in the format UTF8:integer We may want to treat
>
> it as a composite column key and not use a delimiter- to get sorting,
>
> validate the types of the parts of the key, not have to search for the
>
> delimiter and separate the 2 components  manually etc.
>
>
> A third option is to put only data in the column name for students like
>
> Course Name, Teacher Name, 20,21,25 - it would be difficult to identify
>
> that columns with name 20, 21, 25 actually stand for student names - a bit
>
> unreadable.
>
>
> I hope this is not confusing, and would like to hear your thoughts on this.The
> question is
>
> around when you de-normalize & want to have some static info like name ,
>
> and a dynamic list - whats the best way to model this.
>
>
> Regards,
>
> Roshni
>


-- 
Regards and Thanks
Soumya Kanti Acharya

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I just started learning Cassandra any suggestion where to start with ??<br>=
<br><br>Thanks<br>Soumya <br><br><div class=3D"gmail_quote">On Thu, Sep 13,=
 2012 at 10:54 AM, Roshni Rajagopal <span dir=3D"ltr">&lt;<a href=3D"mailto=
:roshni_rajagopal@hotmail.com" target=3D"_blank">roshni_rajagopal@hotmail.c=
om</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">


<div><div dir=3D"ltr">
<div>I want to learn how we can model a mix of static and dynamic columns i=
n a family.</div><div><br></div><div>Consider a course_students col family =
which gives a list of students for a course</div><div>with row key- Course =
Id</div>
<div>Columns - Name, Teach_Nm, StudID1, StudID2, StudID3</div><div>Values -=
 Maths, Prof. Abc, 20,21,25=A0</div><div>where=A0<span style=3D"font-size:1=
0pt">20,21,25 are IDs of students.</span></div><div><span style=3D"font-siz=
e:10pt"><br>
</span></div><div><span style=3D"font-size:10pt">We have</span></div><div>
<p>fixed columns like Course Name, Teacher Name, and a dynamic number of</p=
>
<p>columns like &#39;StudID1&#39;, &#39;StudID2&#39; etc, and my thoughts w=
ere that we could</p>
<p>look for &#39;StudID&#39; and get all the columns with the student Ids i=
n Hector. But the</p>
<p>question was how would we determine the number for the column, like to a=
dd</p>
<p>StudID3 we need to read the row and identify that 2 students are there,<=
/p>
<p>and this is the third one.</p>
<p><br></p>
<p>So we can remove the number in the column name, altogether and keep</p>
<p>columns like Course Name, Teacher Name, Student:20,Student:21, Student:2=
5,</p>
<p>where the second part is the actual student id. However here we run into=
</p>
<p>the second issue that we cannot have some columns of a composite format<=
/p>
<p>and some of another format, when we use static column families- all</p>
<p>columns would need to be in the format UTF8:integer We may want to treat=
</p>
<p>it as a composite column key and not use a delimiter- to get sorting,</p=
>
<p>validate the types of the parts of the key, not have to search for the</=
p>
<p>delimiter and separate the 2 components=A0=A0manually etc.=A0</p>
<p><br></p>
<p>A third option is to put only data in the column name for students like<=
/p>
<p>Course Name, Teacher Name, 20,21,25 - it would be difficult to identify<=
/p>
<p>that columns with name 20, 21, 25 actually stand for student names - a b=
it</p>
<p>unreadable.</p>
<p><br></p>
<p>I hope this is not confusing, and would like to hear your thoughts on th=
is.<span style=3D"font-size:10pt">The question is</span></p><p>around when =
you de-normalize &amp; want to have some static info like name ,</p><p>and =
a dynamic list - whats the best way to model this.</p>
<p><br></p><p>Regards,</p><p>Roshni</p></div> 		 	   		  </div></div>
</blockquote></div><br><br clear=3D"all"><br>-- <br>Regards and Thanks <br>=
Soumya Kanti Acharya<br>

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