Bad performance on RDS MariaDB

Question

I'm migrating an ancient  on-premises 5.5.65 MariaDB to RDS.
The new  RDS MariaDB 10.6 not show CPU, IOPs or Memory problems but the SQLs are too slow.
One complex SELECT cost 0,89 sec on premises and 2,93 using an EC2 in the same VPC.
I have compared the execution plans an are different but probably is because the different versions.

On_premises execution
![On_premises execution](/media/postImages/original/IMJRSsaEmuQnOBhb2tc1fvaw)

EC2 over RDS in the same VPC 
![RDS with EC2](/media/postImages/original/IMHGeRQGjLQ8e65EvruI4SfQ)

I don't know if the differences on the "key" column are relevant to this issue.

Any experience on bad performance with RDS and MariaDB?

Accepted Answer

It seems different optimization was applied. Rowid filtering is an optimization available from MariaDB 10.4.3+, so please disable `rowid_filter` optimizer switch, and re-issue the query.

`SET SESSION optimizer_switch='rowid_filter=off';`, then issue the query.

* https://mariadb.com/kb/en/rowid-filtering-optimization/
* https://mariadb.com/kb/en/server-system-variables/#optimizer_switch

Bad performance on RDS MariaDB

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