You can analyze the query execution plan output to decide whether or not this is necessary. 您可以分析查询执行计划(QEP)输出,以确定这是否是必需的。
Section explains and section actuals are very powerful features to investigate problems with a query execution plan. 在研究查询执行计划(QEP)的问题时,片段解释和片段实绩是非常强大的特性。
Like other relational database management systems such as Oracle and SQL Server, Informix has its internal optimizer, which is responsible for selecting the best query execution plan. 与Oracle和SQLServer等其他关系数据库管理系统一样,Informix也有内部优化器,负责选择最佳的查询执行计划(QEP)。
This file is cumulative, in other words, if you have multiple SQL queries after SET EXPLAIN ON statement, each query execution plan and its costs would be appended to this file until it is removed. 该文件是累积的,换言之,如果SETEXPLAINON语句之后有多个SQL查询,每个查询的执行计划及其成本都会被追加到文件中,直到将之删除。
When an application submits a query to the federated system, the federated server identifies the relevant data sources, and develops a query execution plan for obtaining the requested data. 当应用程序向联邦系统提交一个查询时,联邦服务器识别相关数据源,并生成一个用于获得被请求数据的查询执行计划(QEP)。