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Date: Mon, 3 Aug 2015 17:32:42 -0700
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 <CAEDUwd3uYqun4JYucXnTLy_8siFpG9CEtHVUgusgCs4KzTkU=Q@mail.gmail.com>
Subject: Re: "SELECT *..." query times out on a particular table
From: Robert Coli <rcoli@eventbrite.com>
To: "user@cassandra.apache.org" <user@cassandra.apache.org>
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On Mon, Aug 3, 2015 at 2:48 PM, Sid Tantia <sid.tantia@baseboxsoftware.com>
wrote:

> Any select all or select count query on a particular table is timing out
> with "Cassandra::Errors::TimeoutError: Timed out"
>
> A =E2=80=9CSELECT * FROM <table> WHERE <partition key> =3D =E2=80=98<part=
ition key value>=E2=80=99
> on the table works, but a =E2=80=9CSELECT * FROM <table> LIMIT 1; does no=
t work.
> All other tables and queries work.
>
> Any ideas as to why this might be happening?
>

This specific question is getting to be a FAQ...

Briefly :

1) Cassandra operates best when you supply PRIMARY KEY with your request.
2) The worst case scenario is therefore SELECT * FROM Table;
3) While SELECT * FROM Table; is trivial in a non-distributed RDBMS,
Cassandra is ****NOT A NON-DISTRIBUTED RDBMS**** and so it is NOT TRIVIAL
IN CASSANDRA
4) Cassandra is, instead, a distributed data-store in which most operations
default to a timeout of fewer than a single digit number of seconds
5) So if SELECTing * FROM your Table is likely to take longer than that,
what you'll get is a timeout

The stock remediation for this FAQ is :

a) don't use Cassandra for cases where you need to SELECT * FROM Table
b) if you do have to use it for such a case, use a driver with internal
pagination

=3DRob

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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote">On M=
on, Aug 3, 2015 at 2:48 PM, Sid Tantia <span dir=3D"ltr">&lt;<a href=3D"mai=
lto:sid.tantia@baseboxsoftware.com" target=3D"_blank">sid.tantia@baseboxsof=
tware.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"><u></u>
<div><span><div>Any select all or select count query on a particular table =
is timing out with &quot;Cassandra::Errors::TimeoutError: Timed out&quot;</=
div>
<div><br></div>
<div>A =E2=80=9CSELECT * FROM &lt;table&gt; WHERE &lt;partition key&gt; =3D=
 =E2=80=98&lt;partition key value&gt;=E2=80=99 on the table works, but a =
=E2=80=9CSELECT * FROM &lt;table&gt; LIMIT 1; does not work. All other tabl=
es and queries work.=C2=A0</div>
<div><br></div>
<div>Any ideas as to why this might be happening?</div></span></div></block=
quote><div><br></div><div>This specific question is getting to be a FAQ...<=
/div><div><br></div><div>Briefly :=C2=A0</div><div><br></div><div>1) Cassan=
dra operates best when you supply PRIMARY KEY with your request.=C2=A0</div=
><div>2) The worst case scenario is therefore SELECT * FROM Table;</div><di=
v>3) While SELECT * FROM Table; is trivial in a non-distributed RDBMS, Cass=
andra is ****NOT A NON-DISTRIBUTED RDBMS**** and so it is NOT TRIVIAL IN CA=
SSANDRA</div><div>4) Cassandra is, instead, a distributed data-store in whi=
ch most operations default to a timeout of fewer than a single digit number=
 of seconds</div><div>5) So if SELECTing * FROM your Table is likely to tak=
e longer than that, what you&#39;ll get is a timeout</div><div><br></div><d=
iv>The stock remediation for this FAQ is :</div><div><br></div><div>a) don&=
#39;t use Cassandra for cases where you need to SELECT * FROM Table</div><d=
iv>b) if you do have to use it for such a case, use a driver with internal =
pagination</div><div><br></div><div>=3DRob</div><div><br></div></div></div>=
</div>

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