sql: remove unnecessary scratch resets
sql: remove unnecessary scratch resets

`scratch = encoding[:0]` reset need only once per outer loop iteration,
this patch addresses that.

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