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From: aaron morton <aaron@thelastpickle.com>
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Subject: Re: Changing bloom filter false positive ratio
Date: Fri, 14 Sep 2012 21:08:02 +1200
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I have a hunch that the SSTable selection based on the Min and Max keys =
in ColumnFamilyStore.markReferenced() means that a higher false positive =
has less of an impact.=20

it's just a hunch, i've not tested it.=20

Cheers

-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 14/09/2012, at 4:52 AM, Peter Schuller <peter.schuller@infidyne.com> =
wrote:

>> changing it on some of them.  Can I just change that value through =
the
>> cli and restart or are there any concerns I should have before trying
>> to tweak that parameter?
>=20
> You can change it, you don't have to restart. It will take effect on
> new sstables - flushed and compacted, not on pre-existing sstables.
>=20
> Keep in mind that you can get to about half the size of the default
> (iirc with about 10% fp chance). Beyond that you have extremely
> diminishing returns.
>=20
> --=20
> / Peter Schuller (@scode, http://worldmodscode.wordpress.com)


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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Dus-ascii"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">I =
have a hunch that the SSTable selection based on the Min and Max keys in =
ColumnFamilyStore.markReferenced() means that a higher false positive =
has less of an impact.&nbsp;<div><br></div><div>it's just a hunch, i've =
not tested =
it.&nbsp;</div><div><br></div><div>Cheers</div><div><br><div><div =
apple-content-edited=3D"true">
<span class=3D"Apple-style-span" style=3D"border-collapse: separate; =
color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; =
font-variant: normal; font-weight: normal; letter-spacing: normal; =
line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: =
0px; text-transform: none; white-space: normal; widows: 2; word-spacing: =
0px; -webkit-border-horizontal-spacing: 0px; =
-webkit-border-vertical-spacing: 0px; =
-webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span =
class=3D"Apple-style-span" style=3D"border-collapse: separate; color: =
rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: =
normal; font-weight: normal; letter-spacing: normal; line-height: =
normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: =
normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: =
0px; -webkit-border-vertical-spacing: 0px; =
-webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div =
style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
-webkit-line-break: after-white-space; "><span class=3D"Apple-style-span" =
style=3D"border-collapse: separate; color: rgb(0, 0, 0); font-family: =
Helvetica; font-style: normal; font-variant: normal; font-weight: =
normal; letter-spacing: normal; line-height: normal; orphans: 2; =
text-indent: 0px; text-transform: none; white-space: normal; widows: 2; =
word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; =
-webkit-border-vertical-spacing: 0px; =
-webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div =
style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
-webkit-line-break: after-white-space; "><span class=3D"Apple-style-span" =
style=3D"border-collapse: separate; color: rgb(0, 0, 0); font-family: =
Helvetica; font-style: normal; font-variant: normal; font-weight: =
normal; letter-spacing: normal; line-height: normal; orphans: 2; =
text-indent: 0px; text-transform: none; white-space: normal; widows: 2; =
word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; =
-webkit-border-vertical-spacing: 0px; =
-webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div =
style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
-webkit-line-break: after-white-space; =
"><div><div>-----------------</div><div>Aaron Morton</div><div>Freelance =
Developer</div><div>@aaronmorton</div><div><a =
href=3D"http://www.thelastpickle.com">http://www.thelastpickle.com</a></di=
v></div></div></span></div></span></div></span></span>
</div>

<br><div><div>On 14/09/2012, at 4:52 AM, Peter Schuller &lt;<a =
href=3D"mailto:peter.schuller@infidyne.com">peter.schuller@infidyne.com</a=
>&gt; wrote:</div><br class=3D"Apple-interchange-newline"><blockquote =
type=3D"cite"><blockquote type=3D"cite">changing it on some of them. =
&nbsp;Can I just change that value through the<br>cli and restart or are =
there any concerns I should have before trying<br>to tweak that =
parameter?<br></blockquote><br>You can change it, you don't have to =
restart. It will take effect on<br>new sstables - flushed and compacted, =
not on pre-existing sstables.<br><br>Keep in mind that you can get to =
about half the size of the default<br>(iirc with about 10% fp chance). =
Beyond that you have extremely<br>diminishing returns.<br><br>-- <br>/ =
Peter Schuller (@scode, <a =
href=3D"http://worldmodscode.wordpress.com">http://worldmodscode.wordpress=
.com</a>)<br></blockquote></div><br></div></div></body></html>=

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