Re: v7.2.3 versus v7.3 -> huge performance penalty for JOIN with UNION

(Should probably be in [SQL] by now....)

I've changed my table declarations to agree on the datatypes and only one
simular problem with an update-query doesn't seem to be solved.

(see plan below)

* the concatenation in the lbar select can't be avoided, it's just the way the
data is => this does result in a resulting type 'text', AFAIK

* the aux_address.old_id is also of type 'text'


Still, the planner does a nested loop here against large costs... ;(


Any hints on this (last) one....?



TIA,





Frank.



trial=# explain update address set region_id = lbar.region_id from
    (select debtor_id || '-' || address_seqnr as id, region_id from
        list_base_regions) as lbar, aux_address aa
    where lbar.id = aa.old_id and address.id = aa.id;
                                                      QUERY PLAN
----------------------------------------------------------------------------------------------------------------------
 Merge Join  (cost=1.07..65.50 rows=3 width=253)
   Merge Cond: ("outer".id = "inner".id)
   ->  Nested Loop  (cost=0.00..643707.03 rows=3980 width=28)
         Join Filter: (((("inner".debtor_id)::text || '-'::text) ||
("inner".address_seqnr)::text) = "outer".old_id)
         ->  Index Scan using aux_address_idx2 on aux_address aa
(cost=0.00..81.88 rows=3989 width=16)
         ->  Seq Scan on list_base_regions  (cost=0.00..71.80 rows=3980
width=12)
   ->  Sort  (cost=1.07..1.08 rows=3 width=225)
         Sort Key: address.id
         ->  Seq Scan on address  (cost=0.00..1.05 rows=3 width=225)
               Filter: ((id = 1) IS NOT TRUE)
(10 rows)