DBT-3 Query 2 EXPLAIN ANALYZE differences

From: Mark Wong <markw(at)osdl(dot)org>
To: pgsql-hackers(at)postgresql(dot)org
Subject: DBT-3 Query 2 EXPLAIN ANALYZE differences
Date: 2004-10-26 20:52:06
Message-ID: 20041026135206.A9775@osdl.org
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers

I was doing some testing with DBT-3 on our 8-way STP systems and
noticed a significant difference in the execution of Query 2 using
8.0beta3.

Here is the query template we're using:
select s_acctbal, s_name, n_name, p_partkey, p_mfgr, s_address, s_phone,
s_comment
from part, supplier, partsupp, nation, region
where p_partkey = ps_partkey
and s_suppkey = ps_suppkey
and p_size = :1
and p_type like '%:2'
and s_nationkey = n_nationkey
and n_regionkey = r_regionkey
and r_name = ':3'
and ps_supplycost = ( select min(ps_supplycost)
from partsupp, supplier, nation, region
where p_partkey = ps_partkey
and s_suppkey = ps_suppkey
and s_nationkey = n_nationkey
and n_regionkey = r_regionkey
and r_name = ':3'
)
order by s_acctbal desc, n_name, s_name, p_partkey

This first run executes it pretty fast:
http://khack.osdl.org/stp/298338/ 1555.414 ms

This second run executes it relatively slow:
http://khack.osdl.org/stp/298340/ 42532.855 ms

The plans are different and I suspect thats where the differences lie.
For brevity (and readability) I won't copy the plans here but I'll
provide the links. Search for 'PERF1.POWER.Q2' in the file, it's the
second query executed and you'll notice the differences under the
SubPlan:

The first run:
http://khack.osdl.org/stp/298338/results/run/power_query.result

The second run:
http://khack.osdl.org/stp/298340/results/run/power_query.result

I know Jenny has previously presented a problem that was solved by
doing a setseed(0), but I noticed the kit doesn't do that anymore.
Anyone know if this might be the same or related issues?

Thanks,
Mark

Browse pgsql-hackers by date

  From Date Subject
Next Message Hannu Krosing 2004-10-26 20:53:44 Re: plans for bitmap indexes?
Previous Message Hannu Krosing 2004-10-26 20:44:10 Re: