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From: Nikolay Mihaylov <nmmm@nmmm.nu>
Date: Wed, 7 May 2014 22:31:34 +0300
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Subject: Re: Avoiding email duplicates when registering users
To: user@cassandra.apache.org
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the real question is - if you want the email to be unique, why use
"surrogate" primary key as UUID.

I wonder what UUID gives you at all?

If you want to have non email primary key, why not use md5(email) ?


On Wed, May 7, 2014 at 2:19 AM, Tyler Hobbs <tyler@datastax.com> wrote:

>
> On Mon, May 5, 2014 at 10:27 AM, Ignacio Martin <natx.mc@gmail.com> wrote:
>
>>
>> When a user registers, the server generates a UUID and performs an INSERT
>> ... IF NOT EXISTS into the email_to_UUID table. Immediately after, perform
>> a SELECT from the same table and see if the read UUID is the same that the
>> one we just generated. If it is, we are allowed to INSERT the data in the
>> user table, knowing that no other will be doing it.
>>
>
> INSERT ... IF NOT EXISTS is the correct thing to do here, but you don't
> need to SELECT afterwards.  If the row does exist, the query results will
> show that the insert was not applied and the existing row will be returned.
>
>
> --
> Tyler Hobbs
> DataStax <http://datastax.com/>
>

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<div dir=3D"ltr">the real question is - if you want the email to be unique,=
 why use &quot;surrogate&quot; primary key as UUID.<div><br></div><div>I wo=
nder what UUID gives you at all?</div><div><br></div><div>If you want to ha=
ve non email primary key, why not use md5(email) ?</div>

<div><br></div><div><br></div></div><div class=3D"gmail_extra"><br><br><div=
 class=3D"gmail_quote">On Wed, May 7, 2014 at 2:19 AM, Tyler Hobbs <span di=
r=3D"ltr">&lt;<a href=3D"mailto:tyler@datastax.com" target=3D"_blank">tyler=
@datastax.com</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 dir=3D"ltr"><div class=3D"gmail_extra">=
<div class=3D""><br><div class=3D"gmail_quote">On Mon, May 5, 2014 at 10:27=
 AM, Ignacio Martin <span dir=3D"ltr">&lt;<a href=3D"mailto:natx.mc@gmail.c=
om" target=3D"_blank">natx.mc@gmail.com</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><br></div><div>When a user registers, t=
he server generates a UUID and performs an INSERT ... IF NOT EXISTS into th=
e email_to_UUID table. Immediately after, perform a SELECT from the same ta=
ble and see if the read UUID is the same that the one we just generated. If=
 it is, we are allowed to INSERT the data in the user table, knowing that n=
o other will be doing it.</div>


<div></div></blockquote></div><br></div>INSERT ... IF NOT EXISTS is the cor=
rect thing to do here, but you don&#39;t need to SELECT afterwards.=C2=A0 I=
f the row does exist, the query results will show that the insert was not a=
pplied and the existing row will be returned.<span class=3D"HOEnZb"><font c=
olor=3D"#888888"><br>


<br clear=3D"all"><br>-- <br><font color=3D"#888888">Tyler Hobbs<span></spa=
n><br>
<a href=3D"http://datastax.com/" target=3D"_blank">DataStax</a><br></font>
</font></span></div></div>
</blockquote></div><br></div>

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