It turns out you cannot EXPLAIN on CREATE TABLE AS, but it seems to work
fine if I extend the grammar as below:
ExplainableStmt: SelectStmt | InsertStmt | UpdateStmt | DeleteStmt | DeclareCursorStmt
+ | CreateAsStmt | ExecuteStmt /* by default all are $$=$1 */ ;
It's the same as SELECT INTO after all, which already works. Should
this be added?
