What happens if I revoke access to general pool for an users ?

davidvilladavidvilla Registered User
edited May 25 in Vertica Forum

I have an user which is by default configured to a dedicated high concurrency resource pool. Sometimes request has borrowed memory from general pool as well(GENERAL_MEMORY_BORROWED_KB).

Need to understand what happens if I revoke access to general pool for this user? Would it still continue to borrow memory from general pool?

Answers

  • Jim_KnicelyJim_Knicely Employee, Registered User, VerticaExpert

    Hi,

    Even if you revoke the USAGE privilege on the GENERAL POOL, the "dedicated high concurrency resource pool" can still barrow memory from the GP.

    Example:

    dbadmin=> CREATE USER some_user;
    CREATE USER
    
    dbadmin=> CREATE RESOURCE POOL high_concurreny_pool;
    CREATE RESOURCE POOL
    
    dbadmin=> ALTER RESOURCE POOL high_concurreny_pool MEMORYSIZE '1K' PLANNEDCONCURRENCY 32;
    ALTER RESOURCE POOL
    
    dbadmin=> GRANT USAGE ON RESOURCE POOL high_concurreny_pool TO some_user;
    GRANT PRIVILEGE
    
    dbadmin=> GRANT SELECT ON big_varchar_table TO some_user;
    GRANT PRIVILEGE
    
    dbadmin=> REVOKE USAGE ON RESOURCE POOL general FROM some_user;
    REVOKE PRIVILEGE
    
    dbadmin=> \c - some_user
    You are now connected as user "some_user".
    
    dbadmin=> SHOW resource_pool;
         name      | setting
    ---------------+---------
     resource_pool | general
    (1 row)
    
    dbadmin=> PROFILE SELECT COUNT(*) FROM public.big_varchar_table;
    NOTICE 4788:  Statement is being profiled
    HINT:  Select * from v_monitor.execution_engine_profiles where transaction_id=45035996277124325 and statement_id=2;
    ERROR 8186:  User lacks privileges on resource pool 'general'
    HINT:  Please contact the administrator to receive privileges on the assigned pool or switch to a pool you already have privileges on, using SET SESSION RESOURCE POOL <poolname>
    
    dbadmin=> SET SESSION RESOURCE POOL high_concurreny_pool;
    SET
    
    dbadmin=> SHOW resource_pool;
         name      |       setting
    ---------------+----------------------
     resource_pool | high_concurreny_pool
    (1 row)
    
    dbadmin=> PROFILE SELECT COUNT(*) FROM public.big_varchar_table;
    NOTICE 4788:  Statement is being profiled
    HINT:  Select * from v_monitor.execution_engine_profiles where transaction_id=45035996277124325 and statement_id=5;
    NOTICE 3557:  Initiator memory for query: [on pool high_concurreny_pool: 6916 KB, minimum: 6916 KB]
    NOTICE 5077:  Total memory required by query: [6916 KB]
       COUNT
    ------------
     1000000000
    (1 row)
    

    Note that the query needed 7 KB to run, but the high_concurreny_pool resource pool only has 1 KB, so it borrowed 6 KB from the GP.

  • Jim_KnicelyJim_Knicely Employee, Registered User, VerticaExpert
    edited May 25

    If you do not want the "dedicated high concurrency resource pool" to borrow from the GP, set its MAXMEMORYSIZE to be the same as its MEMORYSIZE.

    Example:

    dbadmin=> \c - dbadmin
    You are now connected as user "dbadmin".
    
    dbadmin=> ALTER RESOURCE POOL high_concurreny_pool MAXMEMORYSIZE '1K';
    ALTER RESOURCE POOL
    
    dbadmin=> SELECT memorysize, maxmemorysize FROM  resource_pools WHERE name = 'high_concurreny_pool';
     memorysize | maxmemorysize
    ------------+---------------
     1K         | 1K
    (1 row)
    
    dbadmin=> \c - some_user
    You are now connected as user "some_user".
    
    dbadmin=> SET SESSION RESOURCE POOL high_concurreny_pool;
    SET
    
    dbadmin=> PROFILE SELECT COUNT(*) FROM public.big_varchar_table;
    NOTICE 4788:  Statement is being profiled
    HINT:  Select * from v_monitor.execution_engine_profiles where transaction_id=45035996277124381 and statement_id=2;
    NOTICE 3557:  Initiator memory for query: [on pool high_concurreny_pool: 6916 KB, minimum: 6916 KB]
    ERROR 3587:  Insufficient resources to execute plan on pool high_concurreny_pool [Request Too Large:Threads Exceeded: Requested = 5, Free = 0 (Limit = 0, Used = 0); File Handles Exceeded: Requested = 2, Free = 0 (Limit = 0, Used = 0); Memory(KB) Exceeded: Requested = 6916, Free = 1 (Limit = 1, Used = 0)]
    

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