Unparsing only a SqlNode sub-tree
During the process of unparsing a SqlNode tree, is there a way to unparse a
subtree to a String then cache its value?
I was thinking I could spawn another SqlWriter from the SqlWriter object
supplied to unparse(), then pull the SQL string fragment from it. But the
SqlWriter isn't cloneable, so there isn't a guaranteed way to ensure the
new SqlWriter is created the same way as the original.