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Hi GB Team, We run experiment analysis with ~5 metrics in Clickhouse, and we have out of memory erro...
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w
Hi GB Team, We run experiment analysis with ~5 metrics in Clickhouse, and we have out of memory errors. It seems that multiple queries are being executed at the same time. Is there a way to run these queries sequentially, and not in parallel? This way we think that there will be enough memory to handle each one of them.
f
You can use fact tables which run as one query
not sure about queuing -
is there a missing index? how much data are you scanning?
w
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+--------------------------------+-----------+----------+-----------------+
|table                           |total_rows |size      |size_uncompressed|
+--------------------------------+-----------+----------+-----------------+
|12go.visit_log_ex               |570134337  |64.47 GiB |274.93 GiB       |
|12go.event_logs                 |703375698  |22.39 GiB |411.06 GiB       |
|12go.mv_log_checkout            |240325231  |20.17 GiB |238.48 GiB       |
|12go.experiment_log_new         |565249790  |17.79 GiB |118.68 GiB
To give the rough idea
f
that's not crazy
what is running out of memory? the query?
w
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500: Code: 241. DB::Exception: Memory limit (total) exceeded: would use 50.89 GiB (attempt to allocate chunk of 12582912 bytes), maximum: 49.43 GiB. OvercommitTracker decision: Query was selected to stop by OvercommitTracker.: While executing JoiningTransform. (MEMORY_LIMIT_EXCEEDED) (version 23.7.4.5 (official build))
While calculating one of the metrics for analysis
We're trying to overcome it now by queuing up the requests at HAproxy level
f
hrmm
thats a huge amount of memory
how many metrics do you have?
5?
I think the queries might need some optimizing
w
I’m being told by our DB guys that clickhouse can’t efficiently execute this kind of queries
f
ya, we know that clickhouse doesn't have great inbuilt optimizers
we know some folks there, if you need some help optimizing
w
Now I’m out of office. I’ll provide the details on Monday, ok? Many thanks for the response
f
sure thing
w
Also the query for the Health tab is a heavy one
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