Return-Path: Delivered-To: apmail-cassandra-user-archive@www.apache.org Received: (qmail 12925 invoked from network); 7 May 2010 11:04:26 -0000 Received: from unknown (HELO mail.apache.org) (140.211.11.3) by 140.211.11.9 with SMTP; 7 May 2010 11:04:26 -0000 Received: (qmail 96757 invoked by uid 500); 7 May 2010 11:04:25 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 96644 invoked by uid 500); 7 May 2010 11:04:23 -0000 Mailing-List: contact user-help@cassandra.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@cassandra.apache.org Delivered-To: mailing list user@cassandra.apache.org Received: (qmail 96636 invoked by uid 99); 7 May 2010 11:04:22 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Fri, 07 May 2010 11:04:22 +0000 X-ASF-Spam-Status: No, hits=2.3 required=10.0 tests=AWL,FREEMAIL_FROM,HTML_MESSAGE,RCVD_IN_DNSWL_NONE,SPF_PASS,T_TO_NO_BRKTS_FREEMAIL X-Spam-Check-By: apache.org Received-SPF: pass (athena.apache.org: domain of vineetdaniel@gmail.com designates 209.85.210.194 as permitted sender) Received: from [209.85.210.194] (HELO mail-yx0-f194.google.com) (209.85.210.194) by apache.org (qpsmtpd/0.29) with ESMTP; Fri, 07 May 2010 11:04:17 +0000 Received: by yxe32 with SMTP id 32so1175062yxe.11 for ; Fri, 07 May 2010 04:03:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:received:in-reply-to :references:date:message-id:subject:from:to:content-type; bh=ZkXXRFB41UyEwK3J+jKrc5xbO+RoWkzm4NkW1wKi+Es=; b=XwDJGSFBNjlI4J1ZANTUuE9RGwYZYThfilThHUVR4yJCeX/spdB2D/AoApKHex+GE2 XfANmmxra83DIMvaUP1MM2atGQZ+YtdKTQkXbdMSXczbRoH04kJiv36DWeBZ+eJRYqJS t1hTz8R7sh3Hu80UezdR7Hf8wC+wXiMQg6cUo= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=jJo1gPIn5Y3tOzLPYMKByv9fUs7oPl4Pf09nDyAfqRwfX1YDZih1idZoU8RogIse6N diXC7UJhRyeazraDLTmSIRRZdnBDJHAkg1gkTsz1eb3GJ90dQtbObQKlBBmkkQMlfS7j CJDp8ra7rlsF+c0Y8p2aRGNlmbYlag1NKq0oU= MIME-Version: 1.0 Received: by 10.150.120.18 with SMTP id s18mr3316959ybc.269.1273230236616; Fri, 07 May 2010 04:03:56 -0700 (PDT) Received: by 10.150.229.11 with HTTP; Fri, 7 May 2010 04:03:56 -0700 (PDT) In-Reply-To: <4BE3F260.7050100@fourkitchens.com> References: <4BE3F260.7050100@fourkitchens.com> Date: Fri, 7 May 2010 16:33:56 +0530 Message-ID: Subject: Re: bloom filter From: vineet daniel To: user@cassandra.apache.org Content-Type: multipart/alternative; boundary=000e0cd70f02f887be0485ff03ab --000e0cd70f02f887be0485ff03ab Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 1. Peter said 'without going to disk' so that means bloom filters reside in memory, always or just when request to that particular CF is made. 2. "It is also important for identifying which SSTable files to look inside even when a key is present." - David can you please throw some more light o= n your point, like what are the implications, why do we need to identify etc. _______________________________________ Vineet Daniel _______________________________________ Let your email find you.... On Fri, May 7, 2010 at 4:28 PM, David Strauss wrote= : > On 2010-05-07 10:55, Peter Sch=C3=BCller wrote: > >> what is the benefit of creating bloom filter when cassandra writes dat= a, > how > >> does it helps ? > > > > It allows Cassandra to answer requests for non-existent keys without > > going to disk, except in cases where the bloom filter gives a false > > positive. > > > > See: > > > > > http://spyced.blogspot.com/2009/01/all-you-ever-wanted-to-know-about.html > > It is also important for identifying which SSTable files to look inside > even when a key is present. > > -- > David Strauss > | david@fourkitchens.com > Four Kitchens > | http://fourkitchens.com > | +1 512 454 6659 [office] > | +1 512 870 8453 [direct] > > --000e0cd70f02f887be0485ff03ab Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 1. Peter said 'without going to disk' so that means bloom filters r= eside in memory, always or just when request to that particular CF is made.=
2. "It is also important for identifying which SSTable files to lo= ok inside
even when a key is present." - David can you please throw some more li= ght on your point, like what are the implications, why do we need to identi= fy etc.


_______________________________________ Vineet Daniel
_______________________________________

Let your em= ail find you....


On Fri, May 7, 2010 at 4:28 PM, David St= rauss <david= @fourkitchens.com> wrote:
On 2010-05-07 10:55, Peter Sch=C3=BCller = wrote:
>> what is the benefit of creating bloom filter when cassandra writes= data, how
>> does it helps ?
>
> It allows Cassandra to answer requests for non-existent keys without > going to disk, except in cases where the bloom filter gives a false > positive.
>
> See:
>
> http://spyced.blogspot.com/2009/01/all-yo= u-ever-wanted-to-know-about.html

It is also important for identifying which SSTable files to loo= k inside
even when a key is present.

--
David Strauss
=C2=A0 | david@fourkitchens.com<= /a>
Four Kitchens
=C2=A0 | http://four= kitchens.com
=C2=A0 | +1 512 454 6659 [office]
=C2=A0 | +1 512 870 8453 [direct]


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