Group算子用于处理GROUP BY子句(节点),对满足条件的元组做分组处理,对应的代码源文件是“nodeGroup.cpp”。Group算子对应的子节点返回的元组是按照分组属性排列的结果。算子对应的主要函数如表7-27所示。 表7-27 Group算子主要函数 ExecInitGroup函数初始Group状态节点。主要执行流程如下。 (1) 构造Group状态节点。 (...
postgres=# SELECT a.usename,b.locktime,a.usesuper FROM pg_user a FULL JOIN pg_user_status b on a.usesysid=b.roloid; --GROUP BY子句示例:根据查询条件过滤,并对结果进行分组。 postgres=# SELECT r_reason_id, AVG(r_reason_sk) FROM tpcds.reason GROUP BY r_reason_id HAVING AVG(r_reaso...
[ ORDER BY {expression [ [ ASC | DESC | USING operator ] | nlssort_expression_clause ] [ NULLS { FIRST | LAST } ]} [, ...] ] [ LIMIT { [offset,] count | ALL } ] [ OFFSET start [ ROW | ROWS ] ] [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ] [ into...
---切换后的备节点: openGauss=# create table t_delay (id int,instime date); ERROR: cannot execute CREATE TABLE in a read-only transaction openGauss=# select now();create table t_delay (id int,instime date); now --- 2023-07-25 10:29:01.915622+08 (1 row) ERROR: cannot execute CRE...
MATCH FULL:不允许一个多字段外键的字段为NULL,除非全部外键字段都是NULL。 MATCH SIMPLE(缺省):允许任意外键字段为NULL。 MATCH PARTIAL:目前暂不支持。 另外,当被参考表中的数据发生改变时,某些操作也会在新表对应字段的数据上执行。ON DELETE子句声明当被参考表中的被参考行被删除时要执行的操作。ON UPDATE子句...
[ GROUP ]role_name|PUBLIC}[, ...][ WITH GRANT OPTION ]wheregrant_on_sequences_clausecanbe:GRANT{ {SELECT|UPDATE|USAGE|ALTER|DROP|COMMENT}[, ...]|ALL[ PRIVILEGES ]}ONSEQUENCESTO{[ GROUP ]role_name|PUBLIC}[, ...][ WITH GRANT OPTION ]wheregrant_on_functions_clausecanbe:GRANT{ {...
bufferFull.snap_wait) *100 /greatest(bufferAccess.snap_wait,1)as walwrite_nowaitfrom (selectcoalesce(snap_2.snap_wait) -coalesce(snap_1.snap_wait,0)as snap_waitfrom (select snap_waitfrom snapshot.snap_global_wait_eventswhere snapshot_id = %ldand snap_event ='WALBufferFull') snap_1, ...
SELinux policy is loaded.SELINUX=disabled# SELINUXTYPE= can take one of these three values:# targeted - Targeted processes are protected,# minimum - Modification of targeted policy. Only selected processes are protected.# mls - Multi Level Security protection.SELINUXTYPE=targeted[root@localhost ~...
{ echo "enable_numa = false" >> "$PGDATA/mot.conf" } # start socket-only postgresql server for setting up or running scripts # all arguments will be passed along as arguments to `postgres` (via pg_ctl) docker_temp_server_start() { if [ "$1" = 'gaussdb' ]; then shift fi # ...
-- 当开启enable_wdr_snapshot参数时,数据库默认每小时自动执行一次snapshot操作。-- 当然特定情况下,也可以手动使用函数创建snapshot,如:select create_wdr_snapshot();postgres=#select*fromsnapshot.snapshotoffset20; snapshot_id | start_ts | end_ts---+---+---21 | 2021-04-21 05:59:09.337877+...