Question

I have arrival column of type timestamp in table reservations ( I’m using postgres ).
How would I select all dates within this year for example?

I know I could do something like this:

select * FROM reservations WHERE extract(year from arrival) = 2012;

But I’ve ran analyze and it looks like it require a sequence scan.
Is there a better option?

P.S. 1 Hmm. both ways seem to require seq. scan. But the one by wildplasser produces results faster – why?

cmm=# EXPLAIN ANALYZE select * FROM reservations WHERE extract(year from arrival) = 2010;
                                                  QUERY PLAN                                                   
---------------------------------------------------------------------------------------------------------------
 Seq Scan on vrreservations  (cost=0.00..165.78 rows=14 width=4960) (actual time=0.213..4.509 rows=49 loops=1)
   Filter: (date_part('year'::text, arrival) = 2010::double precision)
 Total runtime: 5.615 ms
(3 rows)

cmm=# EXPLAIN ANALYZE SELECT * from reservations WHERE arrival > '2010-01-01 00:00:00' AND arrival < '2011-01-01 00:00:00';
                                                                  QUERY PLAN                                                                   
-----------------------------------------------------------------------------------------------------------------------------------------------
 Seq Scan on reservations  (cost=0.00..165.78 rows=51 width=4960) (actual time=0.126..2.491 rows=49 loops=1)
   Filter: ((arrival > '2010-01-01 00:00:00'::timestamp without time zone) AND (arrival < '2011-01-01 00:00:00'::timestamp without time zone))
 Total runtime: 3.144 ms
(3 rows)

** P.S. 2 – After I have created index on arrival column second way got even faster – since it looks like query uses index. Mkey – I guess I’ll stik with this one. **

                                                                       QUERY PLAN                                                                        
---------------------------------------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on reservations  (cost=4.77..101.27 rows=51 width=4960) (actual time=0.359..0.791 rows=49 loops=1)
   Recheck Cond: ((arrival > '2010-01-01 00:00:00'::timestamp without time zone) AND (arrival < '2011-01-01 00:00:00'::timestamp without time zone))
   ->  Bitmap Index Scan on arrival_idx  (cost=0.00..4.76 rows=51 width=0) (actual time=0.177..0.177 rows=49 loops=1)
         Index Cond: ((arrival > '2010-01-01 00:00:00'::timestamp without time zone) AND (arrival < '2011-01-01 00:00:00'::timestamp without time zone))
 Total runtime: 1.265 ms

Answer 1

SELECT * 
FROM reservations 
WHERE arrival >= '2012-01-01'
AND arrival < '2013-01-01'
   ;

BTW if the distribution of values indicates that an index scan will not be the worth (for example if all the values are in 2012), the optimiser could still choose a full table scan. YMMV. Explain is your friend.