I wouldn't call this behavior buggy, but I found it somewhat surprising.
expression_tree_walker() assumes that the walker has already been
invoked on the current node (the node that a given recursive call of
expression_tree_walker() has been invoked on). Therefore, calling
expression_tree_walker() on a primitive node type, such as a Var, is a
no-op.
---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
