sql: misc tracing improvements.
sql: misc tracing improvements.

glycerine/cockroach,vaibhavarora/cockroach,veteranlu/cockroach,petermattis/cockroach,maxlang/cockroach,maxlang/cockroach,glycerine/cockroach,petermattis/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,maxlang/cockroach,cockroachdb/cockroach,paperstreet/cockroach,glycerine/cockroach,cockroachdb/cockroach,petermattis/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,petermattis/cockroach,petermattis/cockroach,cockroachdb/cockroach,maxlang/cockroach,glycerine/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,glycerine/cockroach,maxlang/cockroach,petermattis/cockroach,paperstreet/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,veteranlu/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,paperstreet/cockroach,veteranlu/cockroach,maxlang/cockroach,veteranlu/cockroach,maxlang/cockroach,petermattis/cockroach,vaibhavarora/cockroach,veteranlu/cockroach,glycerine/cockroach,vaibhavarora/cockroach,maxlang/cockroach,glycerine/cockroach,paperstreet/cockroach,paperstreet/cockroach,veteranlu/cockroach,glycerine/cockroach,veteranlu/cockroach,petermattis/cockroach,veteranlu/cockroach