Newsgroups: comp.databases.oracle.server From: hjp-usenet@hjp.at (Peter J. Holzer) Subject: Re: index rebuilding... References: <3EXZ9.53855$GX4.2199677@news2.east.cox.net> <3E39A86C.3143C919@exesolutions.com> <69f6c1c8.0301301921.143657e6@posting.google.com> <998d28f7.0301310721.3c724ec@posting.google.com> <3E3AAC94.B8B6073C@exesolutions.com> <6By_9.37587$jM5.94689@newsfeeds.bigpond.com> Message-ID: User-Agent: slrn/0.9.7.0 (Linux) Date: Sun, 2 Feb 2003 09:32:25 +0100 NNTP-Posting-Host: teal.hjp.at X-Trace: 2 Feb 2003 09:00:00 GMT, teal.hjp.at Lines: 28 Path: news.easynews.com!newsfeed1.easynews.com!easynews.com!easynews!newshosting.com!news-xfer2.atl.newshosting.com!news-hub.siol.net!newscore.univie.ac.at!aconews-feed.univie.ac.at!news.wsr.ac.at!hjp-usenet Xref: newsfeed1.easynews.com comp.databases.oracle.server:174499 X-Received-Date: Sun, 02 Feb 2003 01:59:24 MST (news.easynews.com) On 2003-01-31 17:52, Howard J. Rogers wrote: > I don't know whether it's just a myth or not, but Oracle refers to its > indexes as "B*Tree" structures, not 'b-tree' ones. And that's because the > 'b' doesn't stand for 'binary', but 'balanced'. Not quite. B-trees aren't binary, either. They have basically the same node layout with n-1 keys and n pointers/data items[1], and they are also always balanced. What they do not have is the distinction between branch nodes and leaf nodes. Each node can contain both pointers to other nodes and data. B+trees push all the data down to the leaf nodes and keep only pointers to other nodes in the higher level nodes. B*trees are like b+trees, but use a modified split algorithm to keep the nodes at least 2/3 filled. hp [1] In the case of an index separate from the table, the "data" are pointers into the table. -- _ | Peter J. Holzer | To a database person, |_|_) | Sysadmin WSR | every nail looks like a thumb. | | | hjp@hjp.at | __/ | http://www.hjp.at/ | -- Jamie Zawinski