Needs to be a separate class for the impedance matching to work.

Makes it look less intimidating in doxygen-generated html.

Fix resulting warnings.

It was pretty far up perf top.

Drive-by-change: Fix compiler warning.

This should getting rid of queries using USER-DEFINED.

Also enlarge select lists a bit otherwise the queries in the
restricted scope look too degenerated.

This should getting rid of queries using USER-DEFINED.

It's useful in impedance module as well.

The error rate is rather high for a long time so there are frequent
implicit rollback anyway.