VALUES clause memory optimization (was: Values list-of-targetlists patch...)

Tom Lane wrote:
> I think we could safely list_free the input list in transformInsertRow
> as your patch suggests, which would buy back the 144M part. But I don't
> believe it's safe at all to free the raw_parser output --- the grammar
> sometimes makes multiple links to the same subtree, eg in BETWEEN.

In transformExpr the comment implies that it should be safe to reapply
to an already transformed expression. What if we free the raw_parser
expression list/cells/nodes and replace it with the as-transformed one?

Joe