连接数(总连接数、活跃连接数、等待连接数) QPS(Queries Per Second)/ TPS(Transactions Per Second) 数据库大小、表/索引大小及膨胀情况 缓存命中率(blks_hit/ (blks_hit+blks_read)) 事务相关(最长事务运行时间、最老XID年龄、复制延迟) 后台进程状态(Autovacuum、Checkpointer
7. WITH Queries (Common Table Expressions) 7.1 语法 WITH子句允许你在查询中定义一个临时表,然后在查询中引用它。 WITHregional_salesAS(SELECTregion,SUM(amount)AStotal_salesFROMordersGROUPBYregion),top_regionsAS(SELECTregionFROMregional_salesWHEREtotal_sales>(SELECTSUM(total_sales)/10FROMregional_sales))...
该例中,使用 WITH 定义了两个 CTE, 对应两张表:regional_sales 和 top_regions ,其结果集就是紧随其后的SELECT: SELECTregion,SUM(amount)AStotal_salesFROMordersGROUPBYregion;--regional_sales 结果集SELECTregionFROMregional_salesWHEREtotal_sales>(SELECTSUM(total_sales)/10FROMregional_sales);--top_regions...
postgresql 主从查看 pg数据库主从 本步骤基于Ubuntu 18.04和 Postgresql 10.10 假设主数据库为 192.168.1.109 从数据库为192.168.1.111主数据库配置创建一个新目录1mkdir /var/lib/postgresql/10/main/pgarchive创建流复制帐号首先需要创建一个数据库用户进行主从同步。创建用户replica,并赋予登录和复制的权限1postgres# ...
8 queries 9 top 10 events 我们下面主要说一下 overview, connections ,checkpoint ,top,event 1 OVERVIEW overview 实际上是对整体的POSTGRESQL 的日志中关于系统的语句的执行状态的一个总结. 从页面上看其中主机的整体语句执行的状态都在global status中. ...
This will be explored further in the “Queries” section below. PostgreSQL Query: SELECT * FROM employees; MySQL Query: SELECT * FROM employees; Data Types Both MySQL and PostgreSQL offer a wide range of supported data types, from traditional ones like Integer, Date, and Timestamp...
Knowing what happens during these stages can help diagnose why a query won’t run or runs slowly, and can help you optimize queries to run faster. The psql command line utility uses this protocol exclusively to process queries. Query processing In PostgreSQL, running a query involves s...
transformTopLevelStmt函数负责在调用transformOptionalSelectInto函数之后,将parseTree中的stmt_localtion和stmt_len复制到查询树Query相应字段中。而transformOptionalSelectInfo函数的作用是在select语句中还有INTO时,将其转换为CREATE TABLE AS。 1Query * transformTopLevelStmt(ParseState *pstate, RawStmt *parseTree){2...
[WITH with_queries] SELECT select_list FROM table_expression [sort_specification] 下面几个小节描述选择列表、表表达式和排序声明的细节。WITH查询等高级特性将在最后讨论。 一个简单类型的查询的形式: SELECT * FROM table1; 假设有一个表叫做table1,这条命令将table1中检索所有行和所有用户定义的列(检索的方...
pg_plan_queries:生成执行计划 PushActiveSnapshot CreateDestReceiver:创建接收器,指定SPI接收器 CreateQueryDesc:给执行器创建执行描述符 _SPI_pquery:DML使用Executor执行查询 ExecutorStart ExecutorRun ExecutorFinish ExecutorEnd 代码语言:javascript 代码运行次数:0 运行 AI代码解释 res = _SPI_execute_plan(&plan...