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From: Ali Akhtar <ali.rac200@gmail.com>
Date: Sun, 13 Nov 2016 17:42:26 +0500
Message-ID: <CAKiMtbexaYipVbfAwkTJ=tVADKLF=jQNFeTC7vTS9jB45qkfNA@mail.gmail.com>
Subject: Re: Consistency when adding data to collections concurrently?
To: user@cassandra.apache.org
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archived-at: Sun, 13 Nov 2016 12:42:33 -0000

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Yeah, except I guess there's a minor debate left on whether it'd be more
performant to store the labels in their own table, and do a read query each
time when the parent item is fetched.

Or if they should be kept as a set<label> on the parent item and take the
penalty when updating / deleting labels. (Which will be rare, by the way.)

On Sun, Nov 13, 2016 at 5:38 PM, DuyHai Doan <doanduyhai@gmail.com> wrote:

> So problem solved!
>
> On Sun, Nov 13, 2016 at 1:37 PM, Ali Akhtar <ali.rac200@gmail.com> wrote:
>
>> Yeah, I am using set<label> (not set<text> though)
>>
>> On Sun, Nov 13, 2016 at 5:36 PM, DuyHai Doan <doanduyhai@gmail.com>
>> wrote:
>>
>>> Yes you'd have to know the UDT values since it's part of the primary key
>>> to query your data.
>>>
>>> If I were you I would stick to using a set<text> and use UPDATE my_table
>>> SET labels = labels + <new_label>;
>>>
>>> It does work well with concurrent updates.
>>>
>>> On Sun, Nov 13, 2016 at 1:32 PM, Ali Akhtar <ali.rac200@gmail.com>
>>> wrote:
>>>
>>>> But then how would you query it? You'd need to know all the values of
>>>> the udt, right?
>>>>
>>>> On Sun, Nov 13, 2016 at 5:30 PM, DuyHai Doan <doanduyhai@gmail.com>
>>>> wrote:
>>>>
>>>>> "Also can you make a UDT a clustered key?" --> yes if it's frozen
>>>>>
>>>>> On Sun, Nov 13, 2016 at 1:25 PM, Ali Akhtar <ali.rac200@gmail.com>
>>>>> wrote:
>>>>>
>>>>>> If I wanted to get all values for an item, including its labels, how
>>>>>> would that be done in the above case?
>>>>>>
>>>>>> Also can you make a UDT a clustered key?
>>>>>>
>>>>>> On Sun, Nov 13, 2016 at 4:33 AM, Manoj Khangaonkar <
>>>>>> khangaonkar@gmail.com> wrote:
>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> Instead of using a collection, consider making label a clustered
>>>>>>> column.
>>>>>>>
>>>>>>> With this each request will essentially append a column (label) to
>>>>>>> the partition.
>>>>>>>
>>>>>>> To get all labels would be a simple query
>>>>>>>
>>>>>>> select label from table where partitionkey = "value".
>>>>>>>
>>>>>>> In general , read + update  of a column is an anti pattern in
>>>>>>> cassandra - which is what you are doing. What I suggesting
>>>>>>> above is appending more columns and not updating existing columns.
>>>>>>>
>>>>>>> regards
>>>>>>>
>>>>>>> regards
>>>>>>>
>>>>>>> On Sat, Nov 12, 2016 at 2:34 AM, Ali Akhtar <ali.rac200@gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> I have a table where each record contains a list<string> of labels.
>>>>>>>>
>>>>>>>> I have an endpoint which responds to new labels being added to a
>>>>>>>> record by the user.
>>>>>>>>
>>>>>>>> Consider the following scenario:
>>>>>>>>
>>>>>>>> - Record X, labels = []
>>>>>>>> - User selects 2 labels, clicks a button, and 2 http requests are
>>>>>>>> generated.
>>>>>>>> - The server receives request for Label 1 and Label 2 at the same
>>>>>>>> time.
>>>>>>>> - Both requests see the labels as empty, add 1 label to the
>>>>>>>> collection, and send it.
>>>>>>>> - Record state as label 1 request sees it: [1], as label 2 sees it:
>>>>>>>> [2]
>>>>>>>>
>>>>>>>> How will the above conflict be resolved? What can I do so I end up
>>>>>>>> with [1, 2] instead of either [1] or [2] after both requests have been
>>>>>>>> processed?
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> http://khangaonkar.blogspot.com/
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>

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<div dir=3D"ltr">Yeah, except I guess there&#39;s a minor debate left on wh=
ether it&#39;d be more performant to store the labels in their own table, a=
nd do a read query each time when the parent item is fetched.<div><br></div=
><div>Or if they should be kept as a set&lt;label&gt; on the parent item an=
d take the penalty when updating / deleting labels. (Which will be rare, by=
 the way.)</div></div><div class=3D"gmail_extra"><br><div class=3D"gmail_qu=
ote">On Sun, Nov 13, 2016 at 5:38 PM, DuyHai Doan <span dir=3D"ltr">&lt;<a =
href=3D"mailto:doanduyhai@gmail.com" target=3D"_blank">doanduyhai@gmail.com=
</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin=
:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr">S=
o problem solved!</div><div class=3D"HOEnZb"><div class=3D"h5"><div class=
=3D"gmail_extra"><br><div class=3D"gmail_quote">On Sun, Nov 13, 2016 at 1:3=
7 PM, Ali Akhtar <span dir=3D"ltr">&lt;<a href=3D"mailto:ali.rac200@gmail.c=
om" target=3D"_blank">ali.rac200@gmail.com</a>&gt;</span> wrote:<br><blockq=
uote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc =
solid;padding-left:1ex"><div dir=3D"ltr">Yeah, I am using set&lt;label&gt; =
(not set&lt;text&gt; though)</div><div class=3D"m_4817437728375607835HOEnZb=
"><div class=3D"m_4817437728375607835h5"><div class=3D"gmail_extra"><br><di=
v class=3D"gmail_quote">On Sun, Nov 13, 2016 at 5:36 PM, DuyHai Doan <span =
dir=3D"ltr">&lt;<a href=3D"mailto:doanduyhai@gmail.com" target=3D"_blank">d=
oanduyhai@gmail.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quo=
te" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"=
><div dir=3D"ltr">Yes you&#39;d have to know the UDT values since it&#39;s =
part of the primary key to query your data.<div><br></div><div>If I were yo=
u I would stick to using a set&lt;text&gt; and use UPDATE my_table SET labe=
ls =3D labels + &lt;new_label&gt;;=C2=A0</div><div><br></div><div>It does w=
ork well with concurrent updates.</div></div><div class=3D"m_48174377283756=
07835m_-2718654145488312461HOEnZb"><div class=3D"m_4817437728375607835m_-27=
18654145488312461h5"><div class=3D"gmail_extra"><br><div class=3D"gmail_quo=
te">On Sun, Nov 13, 2016 at 1:32 PM, Ali Akhtar <span dir=3D"ltr">&lt;<a hr=
ef=3D"mailto:ali.rac200@gmail.com" target=3D"_blank">ali.rac200@gmail.com</=
a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0=
 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr">But=
 then how would you query it? You&#39;d need to know all the values of the =
udt, right?</div><div class=3D"m_4817437728375607835m_-2718654145488312461m=
_8201408373775353179HOEnZb"><div class=3D"m_4817437728375607835m_-271865414=
5488312461m_8201408373775353179h5"><div class=3D"gmail_extra"><br><div clas=
s=3D"gmail_quote">On Sun, Nov 13, 2016 at 5:30 PM, DuyHai Doan <span dir=3D=
"ltr">&lt;<a href=3D"mailto:doanduyhai@gmail.com" target=3D"_blank">doanduy=
hai@gmail.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" st=
yle=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div =
dir=3D"ltr">&quot;<span style=3D"font-size:12.8px">Also can you make a UDT =
a clustered key?&quot; --&gt; yes if it&#39;s frozen</span></div><div class=
=3D"m_4817437728375607835m_-2718654145488312461m_8201408373775353179m_39178=
64506403686114HOEnZb"><div class=3D"m_4817437728375607835m_-271865414548831=
2461m_8201408373775353179m_3917864506403686114h5"><div class=3D"gmail_extra=
"><br><div class=3D"gmail_quote">On Sun, Nov 13, 2016 at 1:25 PM, Ali Akhta=
r <span dir=3D"ltr">&lt;<a href=3D"mailto:ali.rac200@gmail.com" target=3D"_=
blank">ali.rac200@gmail.com</a>&gt;</span> wrote:<br><blockquote class=3D"g=
mail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-l=
eft:1ex"><div dir=3D"ltr">If I wanted to get all values for an item, includ=
ing its labels, how would that be done in the above case?<div><br></div><di=
v>Also can you make a UDT a clustered key?</div></div><div class=3D"m_48174=
37728375607835m_-2718654145488312461m_8201408373775353179m_3917864506403686=
114m_3094397286298696524HOEnZb"><div class=3D"m_4817437728375607835m_-27186=
54145488312461m_8201408373775353179m_3917864506403686114m_30943972862986965=
24h5"><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Sun, Nov=
 13, 2016 at 4:33 AM, Manoj Khangaonkar <span dir=3D"ltr">&lt;<a href=3D"ma=
ilto:khangaonkar@gmail.com" target=3D"_blank">khangaonkar@gmail.com</a>&gt;=
</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .=
8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr"><div><div=
><div><div><div>Hi,<br><br></div>Instead of using a collection, consider ma=
king label a clustered column.<br><br></div>With this each request will ess=
entially append a column (label) to the partition.<br><br></div>To get all =
labels would be a simple query<br><br></div>select label from table where p=
artitionkey =3D &quot;value&quot;.<br><br></div><div>In general , read + up=
date=C2=A0 of a column is an anti pattern in cassandra - which is what you =
are doing. What I suggesting<br></div><div>above is appending more columns =
and not updating existing columns.<br><br></div><div>regards<br></div><div>=
<br></div>regards<br></div><div class=3D"gmail_extra"><div><div class=3D"m_=
4817437728375607835m_-2718654145488312461m_8201408373775353179m_39178645064=
03686114m_3094397286298696524m_3891923555445220798h5"><br><div class=3D"gma=
il_quote">On Sat, Nov 12, 2016 at 2:34 AM, Ali Akhtar <span dir=3D"ltr">&lt=
;<a href=3D"mailto:ali.rac200@gmail.com" target=3D"_blank">ali.rac200@gmail=
.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"ma=
rgin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"lt=
r">I have a table where each record contains a list&lt;string&gt; of labels=
.<div><br></div><div>I have an endpoint which responds to new labels being =
added to a record by the user.</div><div><br></div><div>Consider the follow=
ing scenario:</div><div><br></div><div>- Record X, labels =3D []</div><div>=
- User selects 2 labels, clicks a button, and 2 http requests are generated=
.</div><div>- The server receives request for Label 1 and Label 2 at the sa=
me time.</div><div>- Both requests see the labels as empty, add 1 label to =
the collection, and send it.</div><div>- Record state as label 1 request se=
es it: [1], as label 2 sees it: [2]</div><div><br></div><div>How will the a=
bove conflict be resolved? What can I do so I end up with [1, 2] instead of=
 either [1] or [2] after both requests have been processed?</div></div>
</blockquote></div><br><br clear=3D"all"><br></div></div><span class=3D"m_4=
817437728375607835m_-2718654145488312461m_8201408373775353179m_391786450640=
3686114m_3094397286298696524m_3891923555445220798HOEnZb"><font color=3D"#88=
8888">-- <br><div class=3D"m_4817437728375607835m_-2718654145488312461m_820=
1408373775353179m_3917864506403686114m_3094397286298696524m_389192355544522=
0798m_-3346782449632582646gmail_signature" data-smartmail=3D"gmail_signatur=
e"><a href=3D"http://khangaonkar.blogspot.com/" target=3D"_blank">http://kh=
angaonkar.blogspot.co<wbr>m/</a></div>
</font></span></div>
</blockquote></div><br></div>
</div></div></blockquote></div><br></div>
</div></div></blockquote></div><br></div>
</div></div></blockquote></div><br></div>
</div></div></blockquote></div><br></div>
</div></div></blockquote></div><br></div>
</div></div></blockquote></div><br></div>

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