explain, planner and more..

Hi,

how has the following to be read.. (ie. what is the total cost of the
query)... 4.05, 5.88 or ?

Why does the planner choose not to use numberdomain_pkey as index on
numberdomain ?

The table layout is quite bad (due to a lot of last minute-changes)

<snip>
# explain select c.*, (select count(*) from numberservice ns where
ns.customerid=c.customerid and (exists (select * from numbermail nm
where nm.domainnr = ns.domainnr) or exists(select * from numberdomain
nd where nd.domainnr=ns.domainnr))) as amount from customer c where
c.status=0;
NOTICE:  QUERY PLAN:

Seq Scan on customer c  (cost=0.00..4.05 rows=46 width=200)
  SubPlan
    ->  Aggregate  (cost=5.88..5.88 rows=1 width=0)
          ->  Index Scan using numberservice_customerid_ix on
numberservice ns  (cost=0.00..5.88 rows=1 width=0)
                SubPlan
                  ->  Index Scan using numbermail_pkey on numbermail
nm  (cost=0.00..2.01 rows=1 width=47)
                  ->  Seq Scan on numberdomain nd  (cost=0.00..1.85
rows=1 width=31)

EXPLAIN
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