Antw: Performance problem with query - Mailing list pgsql-general

now finally after a long time i have the query plan for the whole filled table. I hope somebody can explain me why it
takesso much longer... 
                                                                            QUERY PLAN

--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
-----
Result  (cost=0.09..254643.09 rows=8044000 width=39) (actual time=0.043..0.043
rows=0 loops=1)
  One-Time Filter: ((((split_part(($1)::text, '_'::text, 2))::smallint = 1) IS
NOT TRUE) AND (((split_part(($2)::text, '_'::text, 2))::smallint = 22) IS NOT TR
UE))
  InitPlan
    ->  Limit  (cost=0.00..0.02 rows=1 width=10) (never executed)
          ->  Seq Scan on temp_table  (cost=0.00..194313.00 rows=8044000 width=
10) (never executed)
    ->  Limit  (cost=0.00..0.02 rows=1 width=10) (actual time=0.006..0.006 rows
=1 loops=1)
          ->  Seq Scan on temp_table  (cost=0.00..194313.00 rows=8044000 width=
10) (actual time=0.004..0.004 rows=1 loops=1)
    ->  Limit  (cost=0.00..0.02 rows=1 width=10) (never executed)
          ->  Seq Scan on temp_table  (cost=0.00..194313.00 rows=8044000 width=
10) (never executed)
  ->  Seq Scan on temp_table  (cost=0.00..194313.00 rows=8044000 width=39) (nev
er executed)
Total runtime: 0.238 ms

Result  (cost=0.06..254643.06 rows=8044000 width=39) (actual time=0.056..655772
.273 rows=8044000 loops=1)
  One-Time Filter: ((split_part(($1)::text, '_'::text, 2))::smallint = 1)
  InitPlan
    ->  Limit  (cost=0.00..0.02 rows=1 width=10) (actual time=0.003..0.003 rows
=1 loops=1)
          ->  Seq Scan on temp_table  (cost=0.00..194313.00 rows=8044000 width=
10) (actual time=0.002..0.002 rows=1 loops=1)
    ->  Limit  (cost=0.00..0.02 rows=1 width=10) (actual time=0.006..0.007 rows
=1 loops=1)
          ->  Seq Scan on temp_table  (cost=0.00..194313.00 rows=8044000 width=
10) (actual time=0.004..0.004 rows=1 loops=1)
  ->  Seq Scan on temp_table  (cost=0.00..194313.00 rows=8044000 width=39) (act
ual time=0.002..191672.344 rows=8044000 loops=1)
Total runtime: 62259544.896 ms

Result  (cost=0.06..254643.06 rows=8044000 width=39) (actual time=1.245..1.245
rows=0 loops=1)
  One-Time Filter: ((split_part(($1)::text, '_'::text, 2))::smallint = 22)
  InitPlan
    ->  Limit  (cost=0.00..0.02 rows=1 width=10) (never executed)
          ->  Seq Scan on temp_table  (cost=0.00..194313.00 rows=8044000 width=
10) (never executed)
    ->  Limit  (cost=0.00..0.02 rows=1 width=10) (actual time=0.013..0.014 rows
=1 loops=1)
          ->  Seq Scan on temp_table  (cost=0.00..194313.00 rows=8044000 width=
10) (actual time=0.009..0.009 rows=1 loops=1)
  ->  Seq Scan on temp_table  (cost=0.00..194313.00 rows=8044000 width=39) (nev
er executed)
Total runtime: 22.270 ms
(31 Zeilen)



>>> "Christian Rengstl" <Christian.Rengstl@klinik.uni-regensburg.de> 13.07.06 8.37 Uhr >>>
Good morning list,

the following query takes about 15 to 20 minutes for around 2 million lines in the file myfile.txt, but with 8 million
linesit takes around 5 hours and i just don't understand why there is such a huge discrepancy in performance. 

COPY public.temp_table FROM 'myfile.txt' WITH DELIMITER '\t';

INSERT INTO public.master(pid,smid, val1, val2, chr)
            SELECT pid, smid, val1, val12, CAST(split_part((SELECT chr from public.temp_table LIMIT 1), '_', 2) as
int2)        
           FROM public.temp_table;

INSERT INTO public.values(smid, pos, chr)
        SELECT DISTINCT smid, pos, CAST(split_part((SELECT chr from public.temp_table LIMIT 1), '_', 2) as int2)
        FROM public.temp_table;

I came up with this query, because i wanted to use the COPY command to load huge files into the db, but i don't want to
loadall the columns contained in the file in only one table but copy some of them into one table and some in a second
table.As i found out with logging, the data is loaded into temp_table within 15 minutes, but to transfer it from the
temp_tabletoagain only something like 10 minutes. Can it be that the cast takes up so much more time than when reading
andtransferring 2 million lines? 

Thanks for any advice!

--
Christian Rengstl M.A.
Klinik und Poliklinik für Innere Medizin II
Kardiologie - Forschung
Universitätsklinikum Regensburg
B3 1.388
Franz-Josef-Strauss-Allee 11
93053 Regensburg
Tel.: +49-941-944-7230


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