PostgreSQL天然集群,多个集群可以组成集簇,有点类似军队的连、团、旅这样的组织规则。对于我们日常学习使用的单节点则是单个集簇单个集群,自己就是集群。 PostgreSQL如何管理这种集群规则?答案是通过一个无符号4个字节的标识进行管理,一个对象就是集群里的一个数据库。 1.2 数据库对象和对象符号标识 数据库对象和对象...
如下 : session_replication_role (enum) Controls firing of replication-related triggers and rules for the current session. Setting this variable requires superuser privilege and results in discarding any previously cached query plans. Possible values are origin (the default), replica and local....
Variables in PostgreSQL are declared using the DECLARE keyword within the DO block or CREATE FUNCTION. Here's the basic syntax: DO $$ DECLARE variable_name data_type [DEFAULT value]; BEGIN -- Statements using the variable END $$; Example 1: Declaring and Using a Variable Code: -- Use an...
\e [FILE] [LINE] edit the query buffer (or file) with external editor \ef [FUNCNAME [LINE]] edit function definition with external editor \p show the contents of the query buffer \r reset (clear) the query buffer \s [FILE] display history or save it to file \w FILE write query ...
Because the query planner does not always choose the optimal join order, advanced users can elect to temporarily set this variable to 1, and then specify the join order they desire explicitly. For more information see Section 14.3.Setting this value to geqo_threshold or more may trigger use ...
上式中的可选项target表示a record variable, a row variable, or a comma-separated list of simple variables and record/row fields。如果要返回结果集,那么需要用到RETURN QUERY的一个变形:RETURN QUERY EXECUTE command-string [ USING expression [, ... ] ]; 参数表达式可以通过USING插入到计算查询字符串中...
define variable for use by custom script -v vacuum all four standard tables before tests,一般测试的时候为了去除上次测试的结果影响,需要vacuum一下pgbench的数据库。 报告说明: transaction type 表明本次测试所使用的测试类型 scaling factor 表明pgbench在初始化时设置的数据量的比例因子 ...
/*** Queryoptimizerentry point** To support loadable plugins that monitor or modify planner behavior,* we provide a hook variable that lets a plugin get control before and* after the standard planning process. The plugin would normally call* standard_planner().** Note to plugin authors: stand...
The default port is indicated by the PGPORT environment variable or the compiled-in default. 4.6.1.3. Performing an SQL dump using pg_dumpall Copy link To dump each database in a given database cluster and to preserve cluster-wide data, ...
mysql> create database one;Query OK, 1 row affected (0.01 sec) mysql> use one; Database changed mysql> create table test_table(id int, name varchar(32)); Query OK, 0 rows affected (0.08 sec) mysql> show tables; +---+ | Tables_in_one | +---+ | one_table | +---+ 1 row...