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Date: Mon, 19 Nov 2012 15:12:11 +0800
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Subject: Re: get_range_slice gets no rowcache support?
From: Manu Zhang <owenzhang1990@gmail.com>
To: user@cassandra.apache.org
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yes, https://issues.apache.org/jira/browse/CASSANDRA-1302
thanks


On Wed, Nov 14, 2012 at 2:04 AM, Tyler Hobbs <tyler@datastax.com> wrote:

> As far as I know, the row cache has never been populated by
> get_range_slices(), only normal gets/multigets.  The behavior is this way
> because get_range_slices() is almost exclusively used to page over an
> entire column family, which generally would not fit into the cache and
> would simply a) ruin your cache if used for gets (b) generate a lot of
> extra garbage, and (c) result in nothing but cache misses.
>
> With that said, I'm sure there are still a few use cases where using the
> cache would be beneficial, so I'm sure there's a ticket out there somewhere
> that presents a few options for supporting this.
>
>
> On Thu, Nov 8, 2012 at 8:39 PM, Manu Zhang <owenzhang1990@gmail.com>wrote:
>
>> I did overlook something. get_range_slice will invoke cfs.getRawCachedRow
>> instead of cfs.getThroughCache. Hence, no row will be cached if it's not
>> present in the row cache. Well, this puzzles me further as to that how the
>> range of rows is expected to get stored into the row cache in the first
>> place.
>>
>> Would someone please clarify it for me? Thanks in advance.
>>
>>
>> On Thu, Nov 8, 2012 at 3:23 PM, Manu Zhang <owenzhang1990@gmail.com>wrote:
>>
>>> I've asked this question before. And after reading the source codes, I
>>> find that get_range_slice doesn't query rowcache before reading from
>>> Memtable and SSTable. I just want to make sure whether I've overlooked
>>> something. If my observation is correct, what's the consideration here?
>>
>>
>>
>
>
> --
> Tyler Hobbs
> DataStax <http://datastax.com/>
>
>

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yes,=A0<a href=3D"https://issues.apache.org/jira/browse/CASSANDRA-1302">htt=
ps://issues.apache.org/jira/browse/CASSANDRA-1302</a>=A0<div>thanks</div><d=
iv class=3D"gmail_extra"><br><br><div class=3D"gmail_quote">On Wed, Nov 14,=
 2012 at 2:04 AM, Tyler Hobbs <span dir=3D"ltr">&lt;<a href=3D"mailto:tyler=
@datastax.com" target=3D"_blank">tyler@datastax.com</a>&gt;</span> wrote:<b=
r>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">As far as I know, the row cache has never be=
en populated by get_range_slices(), only normal gets/multigets.=A0 The beha=
vior is this way because get_range_slices() is almost exclusively used to p=
age over an entire column family, which generally would not fit into the ca=
che and would simply a) ruin your cache if used for gets (b) generate a lot=
 of extra garbage, and (c) result in nothing but cache misses.<br>

<br>With that said, I&#39;m sure there are still a few use cases where usin=
g the cache would be beneficial, so I&#39;m sure there&#39;s a ticket out t=
here somewhere that presents a few options for supporting this.<br><div cla=
ss=3D"gmail_extra">
<div><div class=3D"h5">
<br><br><div class=3D"gmail_quote">On Thu, Nov 8, 2012 at 8:39 PM, Manu Zha=
ng <span dir=3D"ltr">&lt;<a href=3D"mailto:owenzhang1990@gmail.com" target=
=3D"_blank">owenzhang1990@gmail.com</a>&gt;</span> wrote:<br><blockquote cl=
ass=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;p=
adding-left:1ex">

I did overlook something. get_range_slice will invoke cfs.getRawCachedRow i=
nstead of cfs.getThroughCache. Hence, no row will be cached if it&#39;s not=
 present in the row cache. Well, this puzzles me further as to that how the=
 range of rows is expected to get stored into the row cache in the first pl=
ace.<div>


<br></div><div>Would someone please clarify it for me? Thanks in advance.</=
div><div><div><div class=3D"gmail_extra"><br><br><div class=3D"gmail_quote"=
>On Thu, Nov 8, 2012 at 3:23 PM, Manu Zhang <span dir=3D"ltr">&lt;<a href=
=3D"mailto:owenzhang1990@gmail.com" target=3D"_blank">owenzhang1990@gmail.c=
om</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">I&#39;ve asked this question before. And aft=
er reading the source codes, I find that get_range_slice doesn&#39;t query =
rowcache before reading from Memtable and SSTable. I just want to make sure=
 whether I&#39;ve overlooked something. If my observation is correct, what&=
#39;s the consideration here?
</blockquote></div><br></div>
</div></div></blockquote></div><br><br clear=3D"all"><br></div></div><span =
class=3D"HOEnZb"><font color=3D"#888888">-- <br><font color=3D"#888888">Tyl=
er Hobbs<span></span><br>
<a href=3D"http://datastax.com/" target=3D"_blank">DataStax</a><br></font><=
br>
</font></span></div>
</blockquote></div><br></div>

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