Thread: Indexes not used for "min()"

Your name               : Patrick=20
Your email address      : Valsecchi


System Configuration
---------------------
  Architecture (example: Intel Pentium)         : Intel Pentium

  Operating System (example: Linux 2.0.26 ELF)  : Linux 2.4.20

  PostgreSQL version (example: PostgreSQL-7.3.3): PostgreSQL-7.3.3

  Compiler used (example:  gcc 2.95.2)          : gcc 3.2


Please enter a FULL description of your problem:
------------------------------------------------

When doing the following query, it's obvious that postgres should use
the index:

stats=3D# explain select min(time) from call;
                               QUERY PLAN
------------------------------------------------------------------------
 Aggregate  (cost=3D49779.82..49779.82 rows=3D1 width=3D8)
   ->  Seq Scan on stb_call  (cost=3D0.00..44622.06 rows=3D2063106 width=3D=
8)
(2 rows)

stats=3D# \d call
            Table "public.call"
 Column  |           Type           | Modifiers
---------+--------------------------+-----------
 a       | integer                  | not null
 b       | integer                  | not null
 time    | timestamp with time zone | not null
 d       | character varying(4)     |
 e       | character varying(4)     |
 f       | character varying(4)     |
 g       | character varying(15)    | not null
 h       | character varying(7)     |
 i       | smallint                 | not null
Indexes: call_time btree ("time")

stats=3D# select count(*) from call;
  count
---------
 2063106
(1 row)

If you have any question or comment, please contact me directly, I'm not
suscribed to the list.

On Tue, Jul 29, 2003 at 09:48:37 -0600,
  "Valsecchi, Patrick" <patrick.valsecchi@nagrastar.com> wrote:
>
> When doing the following query, it's obvious that postgres should use
> the index:
>
> stats=# explain select min(time) from call;

This has been discussed on the mailing lists numerous times. If you are
interested in details you can search the archives. If you just want a faster
equivalent query use:
select time from call order by time limit 1;