changefeed.memory.per_changefeed_limit
参数调整,现在通过集群设置,会减少对前台延迟的影响。LEFT JOIN
在对not null
约束的虚拟计算列的表进行操作时导致错误的结果。EXPLAIN
在某些复杂场景下运行语句时索引推荐不佳的情况。RESTORE
在恢复的数据时作业会挂起的情况。IMPORT
任务的导入速度。ORDER BY
和 LIMIT
查询的语句性能。DECIMAL
数据类型的大型数据集的算术和聚合速度。select host('192.168.1.5/24');
host
---------------
192.168.1.5
select exp(1.0);
exp
---------------------
2.7182818284590452354
select trim(both 'x' from 'xTomxx')
trim
--------
Tom
select sign(20);
sign
------
1
select broadcast('192.168.1.5/24');
broadcast
--------------------
192.168.1.255/24
select masklen('192.168.1.5/24');
masklen
-----------
24
select netmask('192.168.1.5/24');
netmask
-----------------
255.255.255.0
select hostmask('192.168.23.20/30');
hostmask
------------
0.0.0.3
SHOW DEFAULT PRIVILEGES
子句SHOW DEFAULT PRIVILEGES IN SCHEMA S;
role for_all_roles object_type grantee privilege_type
testuser false tables testuser2 DROP
testuser false tables testuser2 SELECT
testuser false tables testuser2 UPDATE
SHOW SUPER REGIONS FROM DATABASE
语句SHOW SUPER REGIONS FROM DATABASE ABC;
ABC ca-central-sr {ca-central-1}
ABC test {ap-southeast-2,us-east-1}
ALTER DEFAULT PRIVILEGES GRANT ALL ON TABLES TO foo;
CREATE DATABASE dbname WITH OWNER S;
SHOW GRANTS ON table/type/schema...
语句多了is_grantable
列SHOW GRANTS ON DATABASE dbname;
database_name grantee privilege_type is_grantable
dbname admin ALL true
dbname public CONNECT false
dbname root ALL true
dbname s ALL true
RESET
语句,它会将会话变量的值重置为其默认值。RESET session_name;
default_transaction_quality_of_service
,该变量代表会话中提交的SQL请求控制增加后续 SQL请求的准入控制优先级
SET default_transaction_quality_of_service=critical;
要降低后续 SQL请求的准入控制优先级:
SET default_transaction_quality_of_service=background;
要将准入控制优先级重置为默认会话设置(介于背景和关键之间)
SET default_transaction_quality_of_service=regular;
CREATE TABLE foo();
BEGIN;
ALTER TABLE foo RENAME TO bar;
CREATE TABLE foo();
COMMIT;
select unordered_unique_rowid();
1554671853219610625
sql.cross_db_sequence_references.enabled
启用。set sql.cross_db_sequence_references.enabled=dbname;
with comment
子句;SHOW CONSTRAINTS from t with comment;
show create table
不在展示famlily
项show create table t;
CREATE TABLE public.t (
a INT8 NOT NULL,
CONSTRAINT t_pkey PRIMARY KEY (a ASC)
)