Обсуждение: problem with slow select

hi 

I have two tables:

table:    XXXX
idcode varchar(15) -->references (idcode) table YYYY
latitude float
longitude float
time timestamp
p_a char(1)
barcode....
address....
idprog serial... -->primary key
flag boolean

table YYYY
idfact numeric(7,0) --->references .....
idcode varchar(15) --->primary key
name varchar(20)

I want to exctract the last operation of table XXXX for each idcode of
table YYYY where idfact=123

I HAVE THIS QUERY BUT IT IS TOO SLOW (10 SECONDS):

select XXXX.*,YYYY.name from YYYY,XXXX  join (select
XXXX.idcode,max(XXXX.tempo) as tempo from XXXX,YYYY where
YYYY.idfact=123 and XXXX.idcode=YYYY.idcode  group by XXXX.idcode)
temptable on (temptable.tempo=XXXX.tempo and
temptable.idcode=XXXX.idcode) where YYYY.idfact=123 and
XXXX.idcode=YYYY.idcode order by YYYY.name;

PLEASE HELP ME



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On Wed, 2004-04-21 at 11:00, francescosaf wrote:
> hi 
> 
> I have two tables:

Please send results of EXPLAIN ANALYZE for the query in question.

Thanks

thank you for answer and excuse me for later

this is query plan:



QUERY PLAN                                          

---------------------------------------------------------------------------------------------------------------------------------------------------------------
Nested Loop  (cost=10564.42..10853.74 rows=1 width=150) (actual
time=11626.89..12060.36 rows=6 loops=1)
->  Merge Join  (cost=10564.42..10820.69 rows=6 width=131) (actual
time=11626.45..12058.84 rows=6 loops=1)
Merge Cond: (("outer".idcode = "inner".idcode) AND
("outer".time = "inner".time))
->  Sort  (cost=7550.07..7675.40 rows=50134 width=104) (actual
time=8910.91..9031.23 rows=49293 loops=1)
Sort Key: XXXX.idcode, XXXX.time
->  Seq Scan on XXXX  (cost=0.00..1586.34 rows=50134
width=104) (actual time=0.10..852.78 rows=50515 loops=1)
->  Sort  (cost=3014.35..3017.11 rows=1102 width=31) (actual
time=2419.43..2419.45 rows=6 loops=1)
Sort Key: temptable.idcode, temptable.time
->  Subquery Scan temptable  (cost=2876.08..2958.70
rows=1102 width=31) (actual time=2154.84..2419.15 rows=6 loops=1)
->  Aggregate  (cost=2876.08..2958.70 rows=1102
width=31) (actual time=2154.83..2419.10 rows=6 loops=1)
->  Group  (cost=2876.08..2931.16 rows=11016
width=31) (actual time=2066.58..2389.91 rows=19486 loops=1)
->  Sort  (cost=2876.08..2903.62
rows=11016 width=31) (actual time=2066.55..2106.39 rows=19486 loops=1)
Sort Key: XXXX.idcode
->  Hash Join 
(cost=36.50..2136.54 rows=11016 width=31) (actual time=3.41..765.49
rows=19486 loops=1)
Hash Cond: ("outer".idcode
= "inner".idcode)
->  Seq Scan on XXXX 
(cost=0.00..1586.34 rows=50134 width=21) (actual time=0.12..301.87
rows=50515 loops=1)
->  Hash 
(cost=36.48..36.48 rows=7 width=10) (actual time=3.10..3.10 rows=0
loops=1)
->  Seq Scan on YYYY
(cost=0.00..36.48 rows=7 width=10) (actual time=0.13..3.04 rows=6
loops=1)
Filter:
((idazien = 8::numeric) OR (idazien = 1019::numeric))
->  Index Scan using YYYY_pkey on YYYY  (cost=0.00..5.46 rows=1
width=19) (actual time=0.17..0.18 rows=1 loops=6)
Index Cond: (YYYY.idcode = "outer".idcode)
Filter: ((idazien = 8::numeric) OR (idazien = 1019::numeric))
Total runtime: 12065.05 msec
(23 rows)



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