Mystery: functions are slow with group by, but...

Hi there. I appear to have much quicker performance by asking for more work!

First of all, though: can I see the definition of a function in psql?
\df total_live_a4_properties( text )
just gives me the args, return type etc. Hox can I see the AS '...' clause?

Q2:
I have a big performance problem using a function:

create function total_live_a4_properties( text )
returns int4
as
'select count(*) from properties where
status<>''sold'' and status<>''suspended''
and a4 = $1'
language 'sql';

This takes 5-10 _minutes_ :

select a4, total_live_a4_properties( a4 )
from properties group by a4;

There are 5132 records in the properties table, and 64 distinct a4 values.

Explain gives

NOTICE: QUERY PLAN:

Group ( cost=411.70 rows=5112 width=12) -> Sort ( cost=411.70 rows=5112 width=12)   -> Seq Scan on Properties (
cost=411.70rows=5112 width=12)
 

However this next one is < 3 _seconds_!

select a4, count(*), (100*count(*)/total_live_a4_properties( a4 )) as percentage
from properties group by a4;

Explain gives

NOTICE: QUERY PLAN:

Aggregate ( cost=411.70 rows=5112 width=12) Group ( cost=411.70 rows=5112 width=12)   -> Sort ( cost=411.70 rows=5112
width=12)    -> Seq Scan on Properties ( cost=411.70 rows=5112 width=12)
 

Can anyone tell me what's going on?
thanks, al.

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