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From: =?ISO-8859-1?Q?V=EDctor_Hugo_Oliveira_Molinar?= <vhmolinar@gmail.com>
Date: Wed, 20 Mar 2013 00:01:36 -0300
Message-ID: 
 <CA+eqZAxOHzipMPm-vets7zQa_91oTBtqhCxCJRJvS=ADQXGAJg@mail.gmail.com>
Subject: Re: Truncate behaviour
To: user@cassandra.apache.org, Wei Zhu <wz1975@yahoo.com>
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Hum, my bad.

Thank you!

On Tue, Mar 19, 2013 at 11:55 PM, Wei Zhu <wz1975@yahoo.com> wrote:

> There is setting in the cassandra.yaml file which controls that.
>
>
> # Whether or not a snapshot is taken of the data before keyspace truncati=
on
> # or dropping of column families. The STRONGLY advised default of true
> # should be used to provide data safety. If you set this flag to false,
> you will
> # lose data on truncation or drop.
> auto_snapshot: true
>
>
> ----- Original Message -----
> From: "V=EDctor Hugo Oliveira Molinar" <vhmolinar@gmail.com>
> To: user@cassandra.apache.org
> Sent: Tuesday, March 19, 2013 11:50:35 AM
> Subject: Truncate behaviour
>
> Hello guys!
> I'm researching the behaviour for truncate operations at cassandra.
>
>
> Reading the oficial wiki page( http://wiki.apache.org/cassandra/API ) we
> can understand it as:
>
> "Removes all the rows from the given column family."
>
>
> And reading the DataStax page(
> http://www.datastax.com/docs/1.0/references/cql/TRUNCATE ) we can
> understand it as:
> " A TRUNCATE statement results in the immediate, irreversible removal of
> all data in the named column family."
>
>
> But I think there is a missing and important point about truncate
> operations.
> At least at 1.2.0 version, whenever I run a truncate operation, C*
> automatically creates a snapshot file of the column family, resulting in =
a
> fake free disk space.
>
> I'm intentionally mentioning 'fake free disk space' because I only figure=
d
> it out when the machine disk space was at high usage.
>
>
>
>
> - Is it a security C* behaviour of creating snapshots for each CF before
> truncate operation?
> - In my scenario I need to purge my column family data every day.
> I thought that truncate could handle it based at the docs. But it doesnt.
> And since I dont want to manually delete those snapshots, I'd like to kno=
w
> if there is a safe and practical way to perform a daily purge of this CF
> data.
>
>
>
> Thanks in advance!
>

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Hum, my bad.<div><br></div><div>Thank you!<br><div><br><div class=3D"gmail_=
quote">On Tue, Mar 19, 2013 at 11:55 PM, Wei Zhu <span dir=3D"ltr">&lt;<a h=
ref=3D"mailto:wz1975@yahoo.com" target=3D"_blank">wz1975@yahoo.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">There is setting in the cassandra.yaml file =
which controls that.<br>
<br>
<br>
# Whether or not a snapshot is taken of the data before keyspace truncation=
<br>
# or dropping of column families. The STRONGLY advised default of true<br>
# should be used to provide data safety. If you set this flag to false, you=
 will<br>
# lose data on truncation or drop.<br>
auto_snapshot: true<br>
<div class=3D"im"><br>
<br>
----- Original Message -----<br>
From: &quot;V=EDctor Hugo Oliveira Molinar&quot; &lt;<a href=3D"mailto:vhmo=
linar@gmail.com">vhmolinar@gmail.com</a>&gt;<br>
To: <a href=3D"mailto:user@cassandra.apache.org">user@cassandra.apache.org<=
/a><br>
Sent: Tuesday, March 19, 2013 11:50:35 AM<br>
Subject: Truncate behaviour<br>
<br>
Hello guys!<br>
I&#39;m researching the behaviour for truncate operations at cassandra.<br>
<br>
<br>
</div>Reading the oficial wiki page( <a href=3D"http://wiki.apache.org/cass=
andra/API" target=3D"_blank">http://wiki.apache.org/cassandra/API</a> ) we =
can understand it as:<br>
<div class=3D"im"><br>
&quot;Removes all the rows from the given column family.&quot;<br>
<br>
<br>
</div>And reading the DataStax page( <a href=3D"http://www.datastax.com/doc=
s/1.0/references/cql/TRUNCATE" target=3D"_blank">http://www.datastax.com/do=
cs/1.0/references/cql/TRUNCATE</a> ) we can understand it as:<br>
<div class=3D"HOEnZb"><div class=3D"h5">&quot; A TRUNCATE statement results=
 in the immediate, irreversible removal of all data in the named column fam=
ily.&quot;<br>
<br>
<br>
But I think there is a missing and important point about truncate operation=
s.<br>
At least at 1.2.0 version, whenever I run a truncate operation, C* automati=
cally creates a snapshot file of the column family, resulting in a fake fre=
e disk space.<br>
<br>
I&#39;m intentionally mentioning &#39;fake free disk space&#39; because I o=
nly figured it out when the machine disk space was at high usage.<br>
<br>
<br>
<br>
<br>
- Is it a security C* behaviour of creating snapshots for each CF before tr=
uncate operation?<br>
- In my scenario I need to purge my column family data every day.<br>
I thought that truncate could handle it based at the docs. But it doesnt.<b=
r>
And since I dont want to manually delete those snapshots, I&#39;d like to k=
now if there is a safe and practical way to perform a daily purge of this C=
F data.<br>
<br>
<br>
<br>
Thanks in advance!<br>
</div></div></blockquote></div><br></div></div>

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