Path: news.cambrium.nl!textnews.cambrium.nl!feeder3.cambriumusenet.nl!feed.tweaknews.nl!87.79.20.101.MISMATCH!newsreader4.netcologne.de!news.netcologne.de!feeder.erje.net!eu.feeder.erje.net!newsfeed.datemas.de!weretis.net!feeder1.news.weretis.net!news.solani.org!.POSTED!not-for-mail From: Alexander Langer Newsgroups: comp.databases.theory Subject: Re: Query cost Date: Mon, 11 Nov 2013 18:31:09 +0100 Organization: solani.org Lines: 14 Message-ID: References: <96157010-f9eb-414a-a3b7-2b86ef34573b@googlegroups.com> <959f2f3b-19a1-4cdb-8eac-af53cd89468d@googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Trace: solani.org 1384191068 18174 eJwFwYEBwCAIA7CXRGgZ58iw/59gAqfxzyAYEOTdg0WVNPkZ2WFxxm6yj2Pl3epy+V4Y1jwlShE3 (11 Nov 2013 17:31:08 GMT) X-Complaints-To: abuse@news.solani.org NNTP-Posting-Date: Mon, 11 Nov 2013 17:31:08 +0000 (UTC) User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 X-User-ID: eJwFwYEBwDAEBMCVfHhiHFL2H6F3VIe/MKcbl2uaefykq3QMp498gWWVNEL7skghNHAcMBtgb+a897VN/R+JFJU= In-Reply-To: <959f2f3b-19a1-4cdb-8eac-af53cd89468d@googlegroups.com> Cancel-Lock: sha1:XYfMFcvUQx/yAacNEidffc5lsFY= X-NNTP-Posting-Host: eJwFwQkRADAIAzBL4ytMDoyrfwlLwiB46Qh4MEgX8VvILPXuc1qvTXnDKhdJfSvDXk4abD4DXxDV Xref: news.cambrium.nl > yes it is projection (sorry about the font!) > I just wanted a simple approach; like for join br+br*bs using block nested loop join (b=number of blocks) > Does it use sort merge or hash functions cause there is set difference? I suggest to define the runtime of the operations Π, -, x. Think about the data set and about the operands / arguments. For ΠR−S we should have ((rn*rb)-(sn*nb)) costs. So what about the - operator ? If you find an known algorithm for that you can use his runtime.