KingbaseES 时间函数分类

KingbaseES 时间函数有两大类：返回事务开始时间和返回语句执行时的时间。具体函数看以下例子：

test=# select now(),sys_sleep(1),now();
now | sys_sleep | now
-------------------------------+-----------+-------------------------------
2021-09-13 17:00:20.608055+08 | | 2021-09-13 17:00:20.608055+08
(1 row)

test=# select current_time ,sys_sleep(1),current_time;
current_time | sys_sleep | current_time
--------------------+-----------+--------------------
17:00:21.613050+08 | | 17:00:21.613050+08
(1 row)

test=# select transaction_timestamp(),sys_sleep(1),transaction_timestamp();
transaction_timestamp | sys_sleep | transaction_timestamp
-------------------------------+-----------+-------------------------------
2021-09-13 17:00:22.626277+08 | | 2021-09-13 17:00:22.626277+08
(1 row)

test=# select clock_timestamp(),sys_sleep(1),clock_timestamp();
clock_timestamp | sys_sleep | clock_timestamp
-------------------------------+-----------+-------------------------------
2021-09-13 17:00:24.644381+08 | | 2021-09-13 17:00:25.645639+08
(1 row)

test=# select timeofday(),sys_sleep(1),timeofday();
timeofday | sys_sleep | timeofday
-------------------------------------+-----------+-------------------------------------
Mon Sep 13 17:00:25.647681 2021 CST | | Mon Sep 13 17:00:26.650114 2021 CST
(1 row)

clock_timestamp ，timeofday 返回的是函数 执行时刻的时间；而 now, current_time , transaction_timestamp 返回的都是事务开始的时间。

statement_timestamp  比较特殊：

test=# select statement_timestamp(),sys_sleep(1),statement_timestamp();
statement_timestamp | sys_sleep | statement_timestamp
-------------------------------+-----------+-------------------------------
2021-09-13 17:00:23.635612+08 | | 2021-09-13 17:00:23.635612+08
(1 row)

test=# begin;
BEGIN
test=# select statement_timestamp();
      statement_timestamp      
-------------------------------
 2021-09-13 17:04:14.442012+08
(1 row)

test=# select statement_timestamp();
      statement_timestamp      
-------------------------------
 2021-09-13 17:04:20.638240+08
(1 row)

test=# commit;