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Date: Tue, 20 Jul 2010 12:58:29 -0700
Message-ID: <AANLkTiloFo8ZBU4mgV3FgrWkHihhEpUcHiK_dKuauQz-@mail.gmail.com>
Subject: more questions on Cassandra ACID properties
From: Alex Yiu <bigcontentflow@gmail.com>
To: user@cassandra.apache.org
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Hi,

I have more questions on Cassandra ACID properties.
Say, I have a row that has 3 columns already: colA, colB and colC

And, if two *concurrent* clients perform a different insert(...) into the
same row,
one insert is for colD and the other insert is for colE.
Then, Cassandra would guarantee both columns will be added to the same row.

Is that correct?

That is, insert(...) of a column does NOT involving reading and rewriting
other existing columns of the same row?
That is, we do not face the following situation:
client X: read colA, colB and colC; then write: colA, colB, colC and colD
client Y: read colA, colB and colC; then write: colA, colB, colC and colE


BTW, it seems to me that insert() API as described in the wiki page:
http://wiki.apache.org/cassandra/API
should handle updating an existing column as well by the replacing the
existing column value.

If that is the case, I guess we should change the wording from "insert" to
"insert or update" in the wiki doc
And, ideally, insert(...) API operation name would be adapted
to update_or_insert(...)


Looking forward to replies that may confirm my understanding.
Thanks!


Regards,
Alex Yiu

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<div><br></div><div><br></div>Hi,<div><br></div><div>I have more questions =
on=A0Cassandra ACID properties.=A0</div><div>Say, I have a row that has 3 c=
olumns already: colA, colB and colC</div><div><br></div><div>And, if two *c=
oncurrent* clients perform a different=A0insert(...) into the same row,</di=
v>
<div>one insert is for colD and the other insert is for colE.=A0</div><div>=
Then, Cassandra would guarantee both columns will be added to the same row.=
</div><div><br></div><div>Is that correct?=A0</div><div><br></div><div>That=
 is, insert(...) of a column does NOT involving reading and rewriting other=
 existing columns of the same row?=A0</div>
<div>That is, we do not face the following situation:</div><div>client X: r=
ead colA, colB and colC; then write: colA, colB, colC and colD</div><div>cl=
ient Y: read colA, colB and colC; then write: colA, colB, colC and colE</di=
v>
<div><br></div><div><br></div><div>BTW, it seems to me that insert() API as=
 described in the wiki page:=A0</div><div><a href=3D"http://wiki.apache.org=
/cassandra/API">http://wiki.apache.org/cassandra/API</a></div><div>should h=
andle updating an existing column as well by the replacing the existing col=
umn value.</div>
<div><br></div><div>If that is the case, I guess we should change the wordi=
ng from &quot;insert&quot; to &quot;insert or update&quot; in the wiki doc<=
/div><div>And, ideally, insert(...) API operation name would be adapted to=
=A0update_or_insert(...)</div>
<div><br></div><div><br></div><div>Looking forward to replies that may conf=
irm my understanding.</div><div>Thanks!</div><div><br></div><div><br></div>=
<div>Regards,</div><div>Alex Yiu</div><div>=A0</div><div><br></div>

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