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In-Reply-To: <1d69693.3aba.12cb6bd599b.Coremail.sei_wjx@126.com>
References: <1d69693.3aba.12cb6bd599b.Coremail.sei_wjx@126.com>
From: Brandon Williams <driftx@gmail.com>
Date: Sun, 5 Dec 2010 10:54:48 -0600
Message-ID: <AANLkTin93Wug6y38_iYsbY-UiZiKHsG2V83h4Q_rjeVC@mail.gmail.com>
Subject: Re: index file and KeysCached
To: user@cassandra.apache.org
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2010/12/5 =E9=AD=8F=E9=87=91=E4=BB=99 <sei_wjx@126.com>

> for each sstable, there is an index file, which is loaded in memory to
> locate a particular key's offset efficiently.
>

Index files are not held in memory.


> and for each CF, KeysCached can be set to cache keys' location.
> could you pls tell me the difference between the two?
>

KeysCached are held in memory.


> I'm wondering whether it's necessary to set "KeysCached" for a CF or not.
>

Not necessary, but advantageous.

-Brandon

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<div class=3D"gmail_quote">2010/12/5 =E9=AD=8F=E9=87=91=E4=BB=99 <span dir=
=3D"ltr">&lt;<a href=3D"mailto:sei_wjx@126.com">sei_wjx@126.com</a>&gt;</sp=
an><br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-=
left:1px #ccc solid;padding-left:1ex;">

for each sstable, there is an index file, which is loaded in memory to loca=
te a particular key&#39;s offset efficiently.<br></blockquote><div><br></di=
v><div>Index files are not held in memory.</div><div>=C2=A0</div><blockquot=
e class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc sol=
id;padding-left:1ex;">

and for each CF, KeysCached can be set to cache keys&#39; location.<br>coul=
d you pls tell me the difference between the two?<br></blockquote><div><br>=
</div><div>KeysCached are held in memory.</div><div>=C2=A0</div><blockquote=
 class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc soli=
d;padding-left:1ex;">

I&#39;m wondering whether it&#39;s necessary to set &quot;KeysCached&quot; =
for a CF or not.<br></blockquote><div><br></div><div>Not necessary, but adv=
antageous.=C2=A0</div><div><br></div><div>-Brandon</div></div>

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