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Date: Thu, 9 Oct 2014 17:21:41 -0700
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 <CAEDUwd2c0umnPG7Tpbnq9tj_VJQyGW9bsXm_52TBDrR3n5o-KA@mail.gmail.com>
Subject: Re: Deleting counters
From: Robert Coli <rcoli@eventbrite.com>
To: "user@cassandra.apache.org" <user@cassandra.apache.org>
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On Thu, Oct 9, 2014 at 3:29 PM, Robert Wille <rwille@fold3.com> wrote:

> What is the bad thing that happens (or can possibly happen) when a counter
> is deleted?
>

You get totally wacky counter state if you, later, re-create and use it.

https://issues.apache.org/jira/browse/CASSANDRA-6532
and
https://issues.apache.org/jira/browse/CASSANDRA-7346

Have some good discussion.

Is it safe to delete an entire row of counters?


Not unless :
a) you will never use that particular counter row again
OR
b) gc_grace_seconds has passed and you have repaired and run a major
compaction on every node, such that 100% of such tombstones have been
removed


> Is there any 2.0.x version of Cassandra in which it is safe to delete
> counters?


See above, 2.0 is the same as any other version for this behavior.

Is there an access pattern in which it is safe to delete counters in 2.0.x?
>

The summary of the above is that, in practice, it is only safe to delete
counters if you plan to never use that particular counter row again.

=Rob

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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote">On T=
hu, Oct 9, 2014 at 3:29 PM, Robert Wille <span dir=3D"ltr">&lt;<a href=3D"m=
ailto:rwille@fold3.com" target=3D"_blank">rwille@fold3.com</a>&gt;</span> w=
rote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8e=
x;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-styl=
e:solid;padding-left:1ex">What is the bad thing that happens (or can possib=
ly happen) when a counter is deleted?<br></blockquote><div><br></div><div><=
div>You get totally wacky counter state if you, later, re-create and use it=
.</div><div><br></div><div><a href=3D"https://issues.apache.org/jira/browse=
/CASSANDRA-6532">https://issues.apache.org/jira/browse/CASSANDRA-6532</a></=
div><div>and</div><div><a href=3D"https://issues.apache.org/jira/browse/CAS=
SANDRA-7346">https://issues.apache.org/jira/browse/CASSANDRA-7346</a><br></=
div><div>=C2=A0<br></div></div><div>Have some good discussion.</div><div><b=
r></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex=
;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style=
:solid;padding-left:1ex"> Is it safe to delete an entire row of counters? <=
/blockquote><div>=C2=A0</div><div>Not unless :</div><div>a) you will never =
use that particular counter row again<br></div><div>OR</div><div>b) gc_grac=
e_seconds has passed and you have repaired and run a major compaction on ev=
ery node, such that 100% of such tombstones have been removed</div><div>=C2=
=A0<br></div><div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px=
 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-=
left-style:solid;padding-left:1ex">Is there any 2.0.x version of Cassandra =
in which it is safe to delete counters?</blockquote></div><div><br></div><d=
iv>See above, 2.0 is the same as any other version for this behavior.</div>=
<div><br></div><div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0=
px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);borde=
r-left-style:solid;padding-left:1ex">Is there an access pattern in which it=
 is safe to delete counters in 2.0.x?<br></blockquote></div><div><br></div>=
<div>The summary of the above is that, in practice, it is only safe to dele=
te counters if you plan to never use that particular counter row again.</di=
v><div><br></div><div>=3DRob</div><div><br></div><div><br></div><div><br></=
div></div></div></div>

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