performance on insert/update - Mailing list pgsql-sql

I have a big problem of performance, please help me.

it is my work :
first : COPY table1 FROM 'file'        -> 43s,INSERT INTO table2             -> 34s, UPDATE table2                  ->
1mn29s ( =2m 46s : OK)
 

second : COPY table1 FROM 'same file'  -> 1m 10s, INSERT INTO table2            -> 2m 14s, UPDATE table2
-> 5mn 20s ( =8m 44s )
 

third  : COPY table1 FROM 'same file'  -> 1m,  INSERT INTO table2            -> 2m 20s,  UPDATE table2
->7mn 30s ( =10m 50s )
 
...


EXPLAIN UPDATE table2 (first, second and third) :

Merge Join  (cost=0.00..8425.71 rows=1 width=102)
-> Index Scan using index2 on table2(cost=0.00..8320.70 rows=1000
width=42)     SubPlan     ->  Index Scan using table1_pkey on table1  (cost=0.00..8.26
rows=1 width=46)
->  Index Scan using index2 on table2  (cost=0.00..60.00 rows=1000
width=60)
SubPlan ->  Index Scan using index2 on table2  (cost=0.00..10.28 rows=1
width=42)     SubPlan     ->  Aggregate  (cost=8.26..8.26 rows=1 width=4)           ->  Index Scan using table1_pkey on
table1 (cost=0.00..8.26
 
rows=1 width=4)     ->  Index Scan using table1_pkey on table1  (cost=0.00..8.26
rows=1 width=46) ->  Index Scan using index2 on table2  (cost=0.00..10.28 rows=1
width=42)     SubPlan     ->  Aggregate  (cost=8.26..8.26 rows=1 width=4)           ->  Index Scan using table1_pkey on
table1 (cost=0.00..8.26
 
rows=1 width=4)     ->  Index Scan using table1_pkey on table1  (cost=0.00..8.26
rows=1 width=46)


------------------------------------------------------------------------------

.../bin/postmaster -d2 -D .../data -p 19118 -i -N64 -B1024

CREATE TABLE table1 (f1 VARCHAR(20) NOT NULL, date_conn DATETIME NOT
NULL,
time INT4, PRIMARY KEY(f1, date_conn));
CREATE INDEX index1 ON table1( f1, date_conn ) ;

CREATE TABLE table2 (f1 VARCHAR(20),nb INT4,time INT4,tmc INT4,date
DATE);    
CREATE INDEX index2 ON table2( f1, date ) ;

CREATE VIEW view1 AS SELECT f1, ( SELECT COUNT(*) FROM table1         WHERE table1.f1=table2.f1           AND
table1.date_conn::date=table2.date) AS nb,       ( SELECT SUM(table1.time) FROM table1         WHERE
table1.f1=table2.f1          AND table1.date_conn::date=table2.date ) AS time,         date FROM
 
table2 WHERE exists ( SELECT f1, date_conn FROM table1        WHERE table1.f1=table2.f1           AND
table1.date_conn::date=table2.date);
 

CREATE INDEX index_view1 ON view1( f1, date ) ;

------------------------------------------------------------------------------

I have a file 'file' : 20162 tuples. (f1/date_conn/time)

"COPY table_brut FROM 'file' USING DELIMITERS '/';

INSERT INTO table2 SELECT DISTINCT f1, 0, 0, 0, date_conn::date FROM table1 WHERE not exists (     SELECT table2.f1,
table2.date    FROM table2, table1     WHERE table2.f1=table1.f1       AND table2.date=table1.date_conn::date     );
 

UPDATE table2 SET nb=nb+(     SELECT nb FROM view1         WHERE view1.f1=table2.f1           AND
view1.date=table2.date),           temps=time+(     SELECT time FROM view1         WHERE view1.f1=table2.f1
ANDview1.date=table2.date ) 
 
WHERE table2.f1=view1.f1  AND table2.date=view1.date ;

UPDATE table2 SET tmc=time/nb;
DELETE FROM table1;
------------------------------------------------------------------------------

Sorry for my english, and Thanks in advance.
Jerome.