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From: Pavel Stehule on 12 Jan 2010 02:55
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)

Regards
Pavel Stehule

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Prev: [HACKERS] Fix for memory leak in dblink
Next: NOT NULL violation and error-message