maria-discuss team mailing list archive

[Federico Razzoli <federico_raz@xxxxxxxx>]

Weird issue. I'm trying to figure out how the connection pool can add an overhead to a single query. The only case I can think is if you use a network storage engine (Federated, Connect, Spider) pointing to tables on localhost. Is this the case?

More likely... are you sure this problem is caused by the connection pool?
* After the first execution, do a SHOW STATUS. Then FLUSH STATUS. Then execute again and, if it takes long time, do another SHOW STATUS. Post your results here, so we can see what happened.
* While the query takes a long time, try a SHOW PROCESSLIST from another client. See if the connection is waiting for a lock.

Regards
Federico



--------------------------------------------
Mar 14/6/16, Stu Smith <stu26code@xxxxxxxxx> ha scritto:

 Oggetto: [Maria-discuss] Odd behavior with query and connection pool
 A: maria-discuss@xxxxxxxxxxxxxxxxxxx
 Data: Martedì 14 giugno 2016, 03:36
 
 Hello,
   Forgive me for reporting this on the behalf of some
 other developers, I will gather more details as needed.
 
 But the basic problem we're having is with a query
 that:
 
    - is always fast the first time ( < 3 seconds
 )
    - is very slow the following time, when using a
 connection pool (~ 30 seconds)
    - is pretty fast the following time, when not
 using a connection pool (5 or 6 seconds)
 
 This is even on a single DB with no other load.
 
 It's a fairly complicated query with sub queries,
 grouping, and such.
 I've been told it creates two temp tables.
 
 I know this is not a whole lot to go one - but
 are there any pointer for connection pool vs no connection
 pool on a lightly loaded DB?
 
 This was actually tried and reproduced with
 multiple connection pools - hikari-db, c3p0, and apache
 connection pool.
 
 Take care,
   -stu
 
 -----Segue allegato-----
 
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