Checks one mapping of a rename against the input schema, stopping at its
first problem (spec §7.5's five checks, then the collision fix of PLAN
Appendix A): the old column is named and in the input; the new name is
given, is a valid column name (isValidColumnName) and differs from the old
one; neither name appears in another mapping, so a swap or a chain is
refused and the renames can run in any order; no other mapping gives a new
name that differs from it only in case; and the new name is not a column the
input keeps, in any case either (foldColumnName): SQL Server, MemSQL and
DuckDB take order_id and ORDER_ID for one column. A column's own new
case (ORDER_ID to order_id) is fine. Exported so an editor can mark
each row.
Checks one mapping of a rename against the input schema, stopping at its first problem (spec §7.5's five checks, then the collision fix of PLAN Appendix A): the old column is named and in the input; the new name is given, is a valid column name (
isValidColumnName) and differs from the old one; neither name appears in another mapping, so a swap or a chain is refused and the renames can run in any order; no other mapping gives a new name that differs from it only in case; and the new name is not a column the input keeps, in any case either (foldColumnName): SQL Server, MemSQL and DuckDB takeorder_idandORDER_IDfor one column. A column's own new case (ORDER_IDtoorder_id) is fine. Exported so an editor can mark each row.