nested queries with IN statement

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POSTGRESQL BUG REPORT
============================================================================

Your name : Vladimir N.Silyaev
Your email address : vns(at)delta(dot)odessa(dot)ua

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

Operating System (example: Linux 2.0.26 ELF) : FreeBSD 4.0-CURRENT

PostgreSQL version (example: PostgreSQL-6.4.2) : PostgreSQL-6.4.2

Compiler used (example: gcc 2.8.0) : gcc 2.7.2

Please enter a FULL description of your problem:
------------------------------------------------
Very weak execute query with IN statement.

Please describe a way to repeat the problem. Please try to provide a
concise reproducible example, if at all possible:
----------------------------------------------------------------------
1. Create empty database.

2. Create sample table.
create table test1 (
id1 integer primary key,
val1 integer not null
);
create index test1_val1 on test1(val1);

create table test2 (
id2 integer primary key,
val2 varchar(16)
);
create index test2_val2 on test2(val2);

insert into test1 VALUES (1,'1');
insert into test1 VALUES (2,'1');
insert into test1 VALUES (3,'1');
insert into test1 VALUES (4,'1');
insert into test1 VALUES (5,'1');
insert into test1 VALUES (6,'1');
insert into test1 VALUES (7,'1');
insert into test1 VALUES (8,'1');
insert into test1 VALUES (9,'1');
insert into test1 VALUES (10,'1');
insert into test1 VALUES (11,'1');
insert into test1 VALUES (12,'1');
insert into test1 VALUES (13,'1');
insert into test1 VALUES (14,'1');
insert into test1 VALUES (15,'1');
insert into test1 VALUES (16,'1');
insert into test1 VALUES (17,'1');
insert into test1 VALUES (18,'1');
insert into test1 VALUES (19,'1');
insert into test1 VALUES (20,'1');
insert into test1 VALUES (21,'1');
insert into test1 VALUES (22,'1');
insert into test1 VALUES (23,'1');
insert into test1 VALUES (24,'1');
insert into test1 VALUES (25,'1');
insert into test1 VALUES (26,'1');
insert into test1 VALUES (27,'1');
insert into test1 VALUES (28,'1');
insert into test1 VALUES (29,'1');
insert into test1 VALUES (30,'1');
insert into test1 VALUES (31,'1');
insert into test1 VALUES (32,'1');
insert into test1 VALUES (33,'1');
insert into test1 VALUES (34,'1');
insert into test1 VALUES (35,'1');
insert into test1 VALUES (36,'1');
insert into test1 VALUES (37,'1');
insert into test1 VALUES (38,'1');
insert into test1 VALUES (39,'1');
insert into test1 VALUES (40,'1');

insert into test2 VALUES (1,'1');
insert into test2 VALUES (2,'1');
insert into test2 VALUES (3,'1');
insert into test2 VALUES (4,'1');
insert into test2 VALUES (5,'1');
insert into test2 VALUES (6,'1');
insert into test2 VALUES (7,'1');
insert into test2 VALUES (8,'1');
insert into test2 VALUES (9,'1');
insert into test2 VALUES (10,'1');
insert into test2 VALUES (11,'1');
insert into test2 VALUES (12,'1');
insert into test2 VALUES (13,'1');
insert into test2 VALUES (14,'1');
insert into test2 VALUES (15,'1');
insert into test2 VALUES (16,'1');
insert into test2 VALUES (17,'1');
insert into test2 VALUES (18,'1');
insert into test2 VALUES (19,'1');
insert into test2 VALUES (20,'1');
insert into test2 VALUES (21,'1');
insert into test2 VALUES (22,'1');
insert into test2 VALUES (23,'1');
insert into test2 VALUES (24,'1');
insert into test2 VALUES (25,'1');
insert into test2 VALUES (26,'1');
insert into test2 VALUES (27,'1');
insert into test2 VALUES (28,'1');
insert into test2 VALUES (29,'1');
insert into test2 VALUES (30,'1');
insert into test2 VALUES (31,'1');
insert into test2 VALUES (32,'1');
insert into test2 VALUES (33,'1');
insert into test2 VALUES (34,'1');
insert into test2 VALUES (35,'1');
insert into test2 VALUES (36,'1');
insert into test2 VALUES (37,'1');
insert into test2 VALUES (38,'1');
insert into test2 VALUES (39,'1');
insert into test2 VALUES (40,'1');

3. Execute test query.

select id1 from test1 where id1 in (select id1 from test1 where val1 in (select id2 from test2 where val2='0'));

The time of processing this query is not acceptable.

With best regards,
V.Silyaev.