Query profiling on mysql cluster
Hi,
we have installed mysql cluster using the configurator (2 nodes with sql and mgt services and other two nodes with ndb sevice) and we have also installed cmon to monitor it.
After some months of production usage now even simple query are very slow and we don't now what's is going wrong.
We now that mysql cluster performs well on simple query and that it's not optimized for complex query (eg bi) but is it normal that we have a time of 8 seconds for a simple query like this "select DISTINCT cp.campaignID from CAMPAIGN_PLAY cp" when the tables contains 60000 rows ?
According to CMON we are not using disk ad every things is in RAM but query with distinct or group by are very slow and when performed sql node is 100 CPU.
Best regards,
Fabio
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Autoreplay...
The problem was the theaded version ndbmtd which is definetely not an good option when using hyper-v virtual machine (even if each vm has 4 vcore). I don't know if iit's a good option when using vmware hypervisor.
We switched to the single threaded version and now the queries whith distinct and group by are again very fast!
The system was setup with the multithreaded version since day one... so I don't understand why the problem starts only after some months of activities
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Hi,
Thanks for letting us know. THere is probably due to contention. Also, is there anything else running on the physical host. Sometimes, if there are many VMs and many vCores sharing the same physical CPUs then you can get this behavior.
How many cores you run on the physical hosts? How many vcores (summed up on all vms) do you have on the physical host)?
THanks
Johan
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