hello, do I understand correctly, that only string columns are indexed and if I want to filter by a number I should set the dimension type as string?

Yes, as top level fields only strings are dictionary encoded and indexed. However within a nested column numeric elements are also indexed.

thanks that helps a lot

I'm unclear on this...

SELECT Success, SUM("count")
FROM ...
WHERE ...
GROUP BY 1

^ If Status is an integer does this perform poorly due to lack of index?

I don't know that the grouping column indexing matters much .. the indexes are used primarily for initial segment scan filtering. Are you seeing a difference? I.e. can you reingest adding a second "SuccessString" column and check the plan and performance?

I'm testing this now...