explain analyze functionality

Tourtounis Sotiris <tourtoun@csd.uoc.gr> writes:

i have an SQL query of the general type
select att0 from table where 1 <= att0 and att0 < 1000000
to a table of the general format (att0 int4, att1 int4) where there is an
index on att0 and when i run the explain analyze on that question it
returns me the following result:

NOTICE: QUERY PLAN:

Index Scan using index1 on class y (cost=0.00..3662.16 rows=1266 width=4)
(actual time=0.44..4323.38 rows=1000000 loops=1)
Total runtime: 4563.40 msec

doews anyone know each of those two index scans, which are stated there
are unique to which of the two conditions refer: to condition 1 <= att0,
to condition att0 < 1000000 or to the union of those two questions?

It should be using both. As of 7.3 it's possible to tell this from the
EXPLAIN output:

regression=# explain select * from tenk1 where 1 < unique1 and unique1 < 100;
QUERY PLAN
---------------------------------------------------------------------------------
Index Scan using tenk1_unique1 on tenk1 (cost=0.00..353.69 rows=100 width=244)
Index Cond: ((1 < unique1) AND (unique1 < 100))
(2 rows)

but in older releases you have to grovel through EXPLAIN VERBOSE output
if you want to be sure.

regards, tom lane