* UPDATE tab SET col.fld1.subfld1 = x, col.fld2.subfld2 = y
* The two expressions produced by the parser will look like
* FieldStore(col, fld1, FieldStore(placeholder, subfld1, x))
- * FieldStore(col, fld2, FieldStore(placeholder, subfld2, x))
+ * FieldStore(col, fld2, FieldStore(placeholder, subfld2, y))
* However, we can ignore the substructure and just consider the top
* FieldStore or ArrayRef from each assignment, because it works to
* combine these as
* FieldStore(FieldStore(col, fld1,
* FieldStore(placeholder, subfld1, x)),
- * fld2, FieldStore(placeholder, subfld2, x))
+ * fld2, FieldStore(placeholder, subfld2, y))
* Note the leftmost expression goes on the inside so that the
* assignments appear to occur left-to-right.
*