Re: planner or statistical bug on 8.5

> -----Original Message-----
> From: pgsql-hackers-owner@postgresql.org [mailto:pgsql-hackers-
> owner@postgresql.org] On Behalf Of Pavel Stehule
> Sent: Monday, January 11, 2010 11:55 PM
> To: PostgreSQL Hackers
> Cc: Tom Lane
> Subject: [HACKERS] planner or statistical bug on 8.5
> 
> Hello
> 
> I checked query and I was surprised with very strange plan:
> 
> postgres=# create table a(a int primary key);
> NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index
> "a_pkey" for table "a"
> CREATE TABLE
> postgres=# create table b(b int primary key);
> NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index
> "b_pkey" for table "b"
> CREATE TABLE
> postgres=# create table c(c int primary key);
> NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index
> "c_pkey" for table "c"
> CREATE TABLE
> postgres=# ANALYZE ;
> ANALYZE
> postgres=# explain select  a, b from a,b,c;
>                               QUERY PLAN
> -----------------------------------------------------------------------
>  Nested Loop  (cost=0.00..276595350.00 rows=13824000000 width=8)
>    ->  Nested Loop  (cost=0.00..115292.00 rows=5760000 width=8)
>          ->  Seq Scan on a  (cost=0.00..34.00 rows=2400 width=4)
>          ->  Materialize  (cost=0.00..82.00 rows=2400 width=4)
>                ->  Seq Scan on b  (cost=0.00..34.00 rows=2400 width=4)
>    ->  Materialize  (cost=0.00..82.00 rows=2400 width=0)
>          ->  Seq Scan on c  (cost=0.00..34.00 rows=2400 width=0)
> (7 rows)

You have no join columns, so it is a simple product.

Perhaps you meant something like this:
EXPLAIN SELECT a.a, b.b, c.c FROM a a, b b, c c WHERE a.a = b.b AND a.a = c.c