Re: "two time periods with only an endpoint in common do not overlap" ???

Ron <ronljohnsonjr@gmail.com> writes:
> OP refers to the OVERLAP operator (is it an operator), not the tsrange() 
> function.

Indeed.  SQL92 defines OVERLAP thus:

         6) The result of the <overlaps predicate> is the result of the
            following expression:

              ( S1 > S2 AND NOT ( S1 >= T2 AND T1 >= T2 ) )
              OR
              ( S2 > S1 AND NOT ( S2 >= T1 AND T2 >= T1 ) )
              OR
              ( S1 = S2 AND ( T1 <> T2 OR T1 = T2 ) )

where S1 is the smaller of the first range's endpoints and T1 is the
larger; similarly S2/T2 are the smaller/larger of the second range's.
(I gloss over the question of what to do with NULL endpoints; but the
apparent redundancies in the above seem to be meant to define what
happens with NULLs.)

I submit that our description using half-open ranges is clearer than
the spec's.  Nonetheless, they're equivalent.

            regards, tom lane