翻訳と辞書 Words near each other ・ Reverse electron flow ・ Reverse engineering ・ Reverse Expo ・ Reverse factoring ・ Reverse ferret ・ Reverse flow ・ Reverse freedom rides ・ Reverse Gainer ・ Reverse genetics ・ Reverse geocoding ・ Reverse glass painting ・ Reverse graffiti ・ Reverse greenshoe ・ Reverse hierarchy ・ Reverse image search ・ Reverse index ・ Reverse innovation ・ Reverse jigsaw ・ Reverse Krebs cycle ・ Reverse leakage current ・ Reverse learning ・ Reverse Logic ・ Reverse logistics ・ Reverse logistics network modelling ・ Reverse lookup ・ Reverse marketing ・ Reverse Marranos ・ Reverse mathematics ・ Reverse migration ・ Reverse migration (birds) Dictionary Lists mini英和辞書 mini和英辞書 Webster 1913 Latin-English FOLDOC Wikipedia English ウィキペディア

翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Reverse index ： ウィキペディア英語版 Reverse index Database management systems provide multiple types of indexes to improve performance and data integrity across diverse application. Index types include b-trees, bitmaps, and r-trees. In database management systems, a reverse key index strategy reverses the key value before entering it in the index.〔http://richardfoote.wordpress.com/2008/01/14/introduction-to-reverse-key-indexes-part-i/〕 E.g., the value 24538 becomes 83542 in the index. Reversing the key value is particularly useful for indexing data such as sequence numbers, where each new key value is greater than the prior value, i.e., values monotonically increase. Reverse key indexes have become particularly important in high volume transaction processing systems because they reduce contention for index blocks. ==Creating data== Reversed key indexes use b-tree structures, but preprocess key values before inserting them. Simplifying, b-trees place similar values on a single index block, e.g., storing 24538 on the same block as 24539. This makes them efficient both for looking up a specific value and for finding values within a range. However if the application inserts values in sequence, each insert must have access to the newest block in the index in order to add the new value. If many users attempt to insert at the same time, they all must write to that block and have to get in line, slowing down the application. This is particularly a problem in clustered databases, which may require the block to be copied from one computer's memory to another's to allow the next user to perform their insert. Reversing the key spreads similar new values across the entire index instead of concentrating them in any one leaf block. This means that 24538 appears on the same block as 14538 while 24539 goes to a different block, eliminating this cause of contention. (Since 14538 would have been created long before 24538, their inserts don't interfere with each other.) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Reverse index」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.