Aggregate tables and symmetric aggregation

[kuopaz]

https://docs.looker.com/data-modeling/learning-lookml/aggregate_awareness

I have an aggregate table that is built successfully, but isn’t being used in a query when I would expect it to be.

This is the message in the SQL: “The query contains the following measures that cannot roll up.”

I think this is the issue: “Also, if your Explore has joins, verify that your measures aren’t converted to distinct measures (symmetric aggregates) through fanned out joins..”

The section “Symmetric aggregates for Explores with joins” isn’t that clear to me - but implies that the aggregate table won’t be used if the measure is on the one-end table and has used symmetric aggregation to create count distinct, sum distinct or average distinct.

For my case:

If the query results table contains *all* the dimensions in the aggregate table, it will be used and the generated SQL is only a SELECT from the aggregate table.

If the query results table contains only *some* of the dimensions in the aggregate table, it will not be used. In this case the generated SQL would need to include a GROUP BY , as I have seen on other explores and aggregate tables I have.

After all that(!), my questions are:

Am I correct in the above?

If yes, isn’t this quite a big restriction on aggregate awareness as symmetric aggregation on fanouts are commonplace?