Major performance problem after upgrade from 8.3 to 8.4

Hello,

I just upgraded with pg_dump/restore from PostgreSQL 8.3.11 to 8.4.4 but
I'm having major performance problems with a query with many left joins.
Problem is that costs are now very, very, very high (was ok in 8.3).
Analyze has been done. Indexes are of course there.

   ->  Merge Left Join
(cost=1750660.22..4273805884876845789194861338991916289697885665127154313046252183850255795798561612107149662486528.00
rows=238233578115856634454073334945297075430094545596765511255148896328828230572227215727052643001958400
width=16)
         Merge Cond: (l.id = d2000903.fk_id)

Details with execution plan can be found at:
http://www.wiesinger.com/tmp/pg_perf_84.txt

I know that the data model is key/value pairs but it worked well in 8.3. I
need this flexibility.

Any ideas?

Thnx.

Ciao,
Gerhard

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