Re: postmaster core dump

On Mon, Sep 19, 2005 at 03:59:35PM -0400, Tom Lane wrote:
> Patrick Welche  writes:
> > I seem to have an unhappy postgresql:
> 
> Let's see a test case, not a stack trace.

I haven't set up the minimalist test case yet, but the 2 tables involved
are incredibly simple. stats.id is an integer primary key, trans.stats_id
points to it. You just need a query which uses a HashJoin. This time, no
core dump, however:

transatlantic=# set enable_hashjoin=on;
SET
transatlantic=# select timeslice,count(stats_id) from trans,stats where trans.stats_id=stats.id group by timeslice;timeslice | count 
-----------+-------
(0 rows)

transatlantic=# set enable_hashjoin=off;
SET
transatlantic=# select timeslice,count(stats_id) from trans,stats where trans.stats_id=stats.id group by timeslice;     timeslice      | count 
---------------------+-------2005-08-28 00:00:00 |   5862005-08-28 00:00:01 |   3782005-08-28 00:20:00 |   878
...

So, no results with enable_hashjoin=on.

Broken:
                                     QUERY PLAN                                      
--------------------------------------------------------------------------------------GroupAggregate  (cost=326296.78..338449.98 rows=97067 width=12)  ->  Sort  (cost=326296.78..329943.40 rows=1458648 width=12)        Sort Key: stats.timeslice        ->  Hash Join  (cost=4203.88..108728.93 rows=1458648 width=12)              Hash Cond: ("outer".stats_id = "inner".id)              ->  Seq Scan on trans  (cost=0.00..59706.48 rows=1458648 width=4)              ->  Hash  (cost=3292.30..3292.30 rows=123430 width=12)                    ->  Seq Scan on stats  (cost=0.00..3292.30 rows=123430 width=12)

Working:
                                           QUERY PLAN                                             
---------------------------------------------------------------------------------------------------GroupAggregate  (cost=506460.77..518613.97 rows=97067 width=12)  ->  Sort  (cost=506460.77..510107.39 rows=1458648 width=12)        Sort Key: stats.timeslice        ->  Merge Join  (cost=263024.32..288892.93 rows=1458648 width=12)              Merge Cond: ("outer".id = "inner".stats_id)              ->  Index Scan using stats_pkey on stats  (cost=0.00..3688.21 rows=123430 width=12)              ->  Sort  (cost=263024.32..266670.94 rows=1458648 width=4)                    Sort Key: trans.stats_id                    ->  Seq Scan on trans  (cost=0.00..59706.48 rows=1458648 width=4)


I'll make a smaller test case over night..

Cheers,

Patrick