VerticaTips-通过资源池参数MAXQUERYMEMORYSIZE控制每个查询的最大使用内存

在9.1.1版本中新增了一个资源池参数MAXQUERYMEMORYSIZE，通过这个参数可以控制在该资源池运行的每个查询所能使用的最大内存，如果查询所需内存超过这个参数设定，则会报错退出。

dbadmin=> CREATE USER test;  
CREATE USER  
  
dbadmin=> CREATE RESOURCE POOL limited_by_query MAXQUERYMEMORYSIZE '1K';  
CREATE RESOURCE POOL  
  
dbadmin=> GRANT USAGE ON RESOURCE POOL limited_by_query TO test;  
GRANT PRIVILEGE  
  
dbadmin=> GRANT USAGE ON SCHEMA public TO test;  
GRANT PRIVILEGE  
  
dbadmin=> GRANT SELECT ON public.big_table TO test;  
GRANT PRIVILEGE  
  
dbadmin=> \c - test  
You are now connected as user "test".  
  
dbadmin=> SHOW resource_pool;  
name | setting  
---------------+------------------  
resource_pool | limited_by_query  
(1 row)  
  
dbadmin=> SELECT * FROM public.big_table;  
ERROR 8722: The minimal memory required by the query [9224 KB] exceeds the query cap size [1 KB]  
HINT: Increase MAXQUERYMEMORYSIZE parameter of the 'limited_by_query' resource pool