Memory activities to monitor in statistics collector?

I am sorry if this question was asked before.
My postgresql is running on Azure database for Postgresql (ver 12) which runs on cloud platform.

My goal is to observe memory statistics to see if there are any memory suspicious statistics that might be the reason for query OOM .

https://pganalyze.com/docs/log-insights/server/S5

The guide Microsoft has is too general to detect query OOM.

https://azure.microsoft.com/ja-jp/blog/best-practices-for-alerting-on-metrics-with-azure-database-for-postgresql-monitoring/

Thus I was thinking if there are any statistics I can monitor.

"/proc/*/smaps" seems to be one option but it's not a choice for me.

https://www.depesz.com/2012/06/09/how-much-ram-is-postgresql-using/

Would there be any statistics or any combination of stat items which can lead to query OOM ?

https://www.postgresql.org/docs/12/monitoring-stats.html

Best Regards,
Yu Watanabe
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