-- time check
CREATE TABLE timetmp (a time);
\copy timetmp from 'data/time.data'
SET enable_seqscan=on;
SELECT count(*) FROM timetmp WHERE a <  '10:57:11';
 count 
-------
   251
(1 row)

SELECT count(*) FROM timetmp WHERE a <= '10:57:11';
 count 
-------
   252
(1 row)

SELECT count(*) FROM timetmp WHERE a  = '10:57:11';
 count 
-------
     1
(1 row)

SELECT count(*) FROM timetmp WHERE a >= '10:57:11';
 count 
-------
   293
(1 row)

SELECT count(*) FROM timetmp WHERE a >  '10:57:11';
 count 
-------
   292
(1 row)

SELECT a, a <-> '10:57:11' FROM timetmp ORDER BY a <-> '10:57:11' LIMIT 3;
    a     |    ?column?     
----------+-----------------
 10:57:11 | @ 0
 10:57:10 | @ 1 sec
 10:55:32 | @ 1 min 39 secs
(3 rows)

CREATE INDEX timeidx ON timetmp USING gist ( a );
SET enable_seqscan=off;
SELECT count(*) FROM timetmp WHERE a <  '10:57:11'::time;
 count 
-------
   251
(1 row)

SELECT count(*) FROM timetmp WHERE a <= '10:57:11'::time;
 count 
-------
   252
(1 row)

SELECT count(*) FROM timetmp WHERE a  = '10:57:11'::time;
 count 
-------
     1
(1 row)

SELECT count(*) FROM timetmp WHERE a >= '10:57:11'::time;
 count 
-------
   293
(1 row)

SELECT count(*) FROM timetmp WHERE a >  '10:57:11'::time;
 count 
-------
   292
(1 row)

EXPLAIN (COSTS OFF)
SELECT a, a <-> '10:57:11' FROM timetmp ORDER BY a <-> '10:57:11' LIMIT 3;
                          QUERY PLAN                          
--------------------------------------------------------------
 Limit
   ->  Index Only Scan using timeidx on timetmp
         Order By: (a <-> '10:57:11'::time without time zone)
(3 rows)

SELECT a, a <-> '10:57:11' FROM timetmp ORDER BY a <-> '10:57:11' LIMIT 3;
    a     |    ?column?     
----------+-----------------
 10:57:11 | @ 0
 10:57:10 | @ 1 sec
 10:55:32 | @ 1 min 39 secs
(3 rows)