Update and delete operations in Clickhouse of data warehouse series

Test data

select count(*) from system.columns where table='test_update';
select count(*) from test_update;

Specific deletion & Update implementation

 grammar   as follows ：
ALTER TABLE <table_name> DELETE WHERE <filter>;
ALTER TABLE <table_name> UPDATE col1 = expr1, ... WHERE <filter>;

ALTER TABLE test_update UPDATE event_status_key=0 where event_status_key=22;

 The command is executed asynchronously , You can view the table  system.mutations  To check whether the command has been executed .

Clickhouse The update operation has some limitations ：
 Index columns cannot be updated ;
 Distributed tables cannot be updated ;
ALTER TABLE UPDATE/DELETE Distributed... Is not supported DDL, So you need to manually on each node in a distributed environment local To update / Delete data ;
 Not suitable for frequent updates or point Update due to Clickhouse The update operation is very resource intensive , If you update frequently , The cluster may collapse , Please operate carefully .

Reference material ：
http://t.zoukankan.com/wenBlog-p-15745238.html stay clickhouse Update and delete in