"append" takes a lot of time in a query

Hello,

I have a strange performance problem with postgresql 8.3 (shipped with ubuntu
hardy) and a query that seems very simple:

explain analyze
    SELECT * FROM (part LEFT OUTER JOIN part_lang ON part.id = part_lang.id)
    WHERE  part.parent = 49110;

query plan here: http://front7.smartlounge.be/~kervel/queryplan.txt

the query does not return a single row

the table "part" and "part_lang" have a whole lot of tables inheriting them,
most of the inheriting tables only contain a few rows.

this turns this query in an append of a whole lot of seq scan/ index scan's.
These scans are predictably quick, but the "append" takes 5 seconds (and the
numbers of the scans do not add up to the append actual time)

if i leave out the "outer join" performance is okay:
 SELECT * FROM part  WHERE  part.parent = 49110;

if i then add a "order by sequence number" the performance is bad again:
SELECT * FROM part  WHERE  part.parent = 49110 order by sequencenumber;

I'm a bit stuck with this problem, and i don't know how to continue finding
out why.

Does someone have an explanation / possible solution for this performance ?

We use a similar scheme on a lot of other projects without problems (but this
time, the number of tables inheriting from part is a bit bigger).

Thanks a lot in advance,
greetings,
Frank

--

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Frank Dekervel
frank.dekervel@smartlounge.be
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Smartlounge
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