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From: Bo Finnerup Madsen <bo.gundersen@gmail.com>
Date: Mon, 11 Apr 2016 06:00:07 +0000
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 <CAHTFYeDfAcg3Us8_-jsLj-gbqd=QpwvWaZK9shq5BxdtFkCZtw@mail.gmail.com>
Subject: Re: Data modelling, including cleanup
To: user@cassandra.apache.org
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Hi Hannu,

Thank you for the pointer. We ended up using materialized views in
cassandra 3.0.3. Seems to do the trick :)


tor. 17. mar. 2016 kl. 11.16 skrev Hannu Kr=C3=B6ger <hkroger@gmail.com>:

> Hi,
>
> That=E2=80=99s how I have done it in many occasions. Nowadays there is th=
e
> possibility use Cassandra 3.0 and materialised views so that you don=E2=
=80=99t need
> to keep two tables up to date manually:
> http://www.datastax.com/dev/blog/new-in-cassandra-3-0-materialized-views
>
> Hannu
>
> On 17 Mar 2016, at 12:05, Bo Finnerup Madsen <bo.gundersen@gmail.com>
> wrote:
>
> Hi,
>
> We are pretty new to data modelling in cassandra, and are having a bit of
> a challenge creating a model that caters both for queries and updates.
>
> Let me try to explain it using the users example from
> http://www.datastax.com/dev/blog/basic-rules-of-cassandra-data-modeling
>
> They define two tables used for reading users, one by username and one by
> email.
> ---------------------------------------------------------------------
> CREATE TABLE users_by_username (
>     username text PRIMARY KEY,
>     email text,
>     age int
> )
>
> CREATE TABLE users_by_email (
>     email text PRIMARY KEY,
>     username text,
>     age int
> )
> ---------------------------------------------------------------------
>
> Now lets pretend that we need to delete a user, and we are given a
> username as a key. Would the correct procedure be:
> 1) Read the email from users_by_username using the username as a key
> 2) Delete from users_by_username using the username as a key
> 3) Delete from users_by_email using the email as a key
>
> Or is there a smarter way of doing this?
>
> Yours sincerely,
>   Bo Madsen
>
>
>

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<div dir=3D"ltr"><div>Hi Hannu,<br><br></div>Thank you for the pointer. We =
ended up using materialized views in cassandra 3.0.3. Seems to do the trick=
 :)<br><br></div><br><div class=3D"gmail_quote"><div dir=3D"ltr">tor. 17. m=
ar. 2016 kl. 11.16 skrev Hannu Kr=C3=B6ger &lt;<a href=3D"mailto:hkroger@gm=
ail.com">hkroger@gmail.com</a>&gt;:<br></div><blockquote class=3D"gmail_quo=
te" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"=
><div style=3D"word-wrap:break-word">Hi,<div><br></div><div>That=E2=80=99s =
how I have done it in many occasions. Nowadays there is the possibility use=
 Cassandra 3.0 and materialised views so that you don=E2=80=99t need to kee=
p two tables up to date manually:<div><a href=3D"http://www.datastax.com/de=
v/blog/new-in-cassandra-3-0-materialized-views" target=3D"_blank">http://ww=
w.datastax.com/dev/blog/new-in-cassandra-3-0-materialized-views</a></div></=
div></div><div style=3D"word-wrap:break-word"><div><div><div><br></div><div=
>Hannu</div></div></div></div><div style=3D"word-wrap:break-word"><div><div=
><div><br><div><blockquote type=3D"cite"><div>On 17 Mar 2016, at 12:05, Bo =
Finnerup Madsen &lt;<a href=3D"mailto:bo.gundersen@gmail.com" target=3D"_bl=
ank">bo.gundersen@gmail.com</a>&gt; wrote:</div><br><div><div dir=3D"ltr"><=
div>Hi,</div><div><br></div><div>We are pretty new to data modelling in cas=
sandra, and are having a bit of a challenge creating a model that caters bo=
th for queries and updates.</div><div><br></div><div>Let me try to explain =
it using the users example from <a href=3D"http://www.datastax.com/dev/blog=
/basic-rules-of-cassandra-data-modeling" target=3D"_blank">http://www.datas=
tax.com/dev/blog/basic-rules-of-cassandra-data-modeling</a></div><div><br><=
/div><div>They define two tables used for reading users, one by username an=
d one by email.</div><div>-------------------------------------------------=
--------------------</div><div>CREATE TABLE users_by_username (</div><div>=
=C2=A0 =C2=A0 username text PRIMARY KEY,</div><div>=C2=A0 =C2=A0 email text=
,</div><div>=C2=A0 =C2=A0 age int</div><div>)</div><div>=C2=A0</div><div>CR=
EATE TABLE users_by_email (</div><div>=C2=A0 =C2=A0 email text PRIMARY KEY,=
</div><div>=C2=A0 =C2=A0 username text,</div><div>=C2=A0 =C2=A0 age int</di=
v><div>)</div><div>--------------------------------------------------------=
-------------</div><div><br></div><div>Now lets pretend that we need to del=
ete a user, and we are given a username as a key. Would the correct procedu=
re be:</div><div>1) Read the email from users_by_username using the usernam=
e as a key</div><div>2) Delete from users_by_username using the username as=
 a key</div><div>3) Delete from users_by_email using the email as a key</di=
v><div><br></div><div>Or is there a smarter way of doing this?</div><div><b=
r></div><div>Yours sincerely,</div><div>=C2=A0 Bo Madsen</div><div><br></di=
v></div>
</div></blockquote></div><br></div></div></div></div></blockquote></div>

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