跟大部分容器一样,b_plus_tree也有迭代器;而这里的index_iterator是为了实现对叶节点的遍历,IndexScanExecutor是一个执行遍历的类,在真正执行的时候会调用b_plus_tree去遍历,但由于应对大量数据查询避免内存过大的考虑,数据库不会希望一次性全部给出数据,所以要使用迭代器记录当前移动位置; 由于支持多线程并发,对页面...
The B+ Tree is a variation of the B tree that supports additional efficient insertion, deletion and operations beyond those of the B tree. Each element in the B+ tree has three operations Searching associated with it: Insertion, Deletion, and Balancing. To remove a node, we first search fo...
高效:SELECT * FROM EMP WHERE DEPTNO >=4 低效: SELECT * FROM EMP WHERE DEPTNO >3 两者的区别在于,前者DBMS将直接跳到第一个DEPT等于4的记录而后者将首先定位到DEPTNO=3的记录并且向前扫描到第一个DEPT大于3的记 录。 (24)用UNION替换OR (适用于索引列): 通常情况下,用UNION替换WHERE子句中的OR将会起...
(5) 在SQL*Plus , SQL*Forms和Pro*C中重新设置ARRAYSIZE参数, 可以增加每次数据库访问的检索数据量 ,建议值为200 (6) 使用DECODE函数来减少处理时间: 使用DECODE函数可以避免重复扫描相同记录或重复连接相同的表. (7) 整合简单,无关联的数据库访问:
In this paper, we propose a novel multi-version B^+-tree index structure, called block-based multi-version B^+-tree ( BbMVBT), for indexing multi-versions ... Wang,Jiantao,Lam,... - 《IEEE Transactions on Computers》 被引量: 4发表: 2015年 Flash-Optimized B plus -Tree With the rap...
Most Server Manager scripts should work in a SQL*Plus environment, but some scripts may need to be modified. xxxiii xxxiv 1 Oracle Database Architecture on Windows This chapter describes how Oracle Database architecture takes advantage of some of the more advanced services in Windows operating ...
While B+Tree is the most important index structure for disk-based database management systems (DBMS), T*-Tree is optimized for main memory access and widely used for in memory database system (IMDB). however, the prior researches made performance evaluation between T*-Tree and B+Tree on ...
In theSTARTWITHclause, you specify a condition that identifies the root of the tree. You specify the direction in which the query walks the tree (down from the root or up from the branches) with thePRIORoperator. ROWID ROWIDreturns the rowid (binary address) of a row in a database table...
import { ElMessage } from 'element-plus'; import DbSelectTree from '@/views/ops/db/component/DbSelectTree.vue'; Expand Down 6 changes: 5 additions & 1 deletion 6 mayfly_go_web/src/views/ops/db/api.ts Show comments View file Edit file Delete file This file contains bidirectional ...
DBMS MySQL 5.7.x Thelog_bin_trust_function_creatorsoption must be enabled. MariaDB 10.1.x Thelog_bin_trust_function_creatorsoption must be enabled. Postgres 9.x MS-SQL 201x Supported client web-browsers: Firefox Internet Explorer 9.x or greater ...