I am about to rip out the code that supports multiple indexscans for OR
conditions inside a single IndexScan plan node. As best I can tell,
the new-style bitmap-OR code is as fast or faster than the old way
even in fully cached test cases (ie, with no allowance for improved
efficiency of disk access). So there's no percentage in maintaining
support for the old way, and getting rid of it will allow simplification
of code and data structures in the planner.
regards, tom lane