Execution plan changed after upgrade from 7.3.9 to 8.2.3

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Subject: Execution plan changed after upgrade from 7.3.9 to 8.2.3
Date: ,
Msg-id: 45F65EA3.1030706@leroymerlin.fr
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Responses: Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Michael Fuhr)
List: pgsql-performance

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Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )
 Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Michael Fuhr, )
  Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )
   Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Richard Huxton, )
    Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )
     Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  ("Dave Dutcher", )
      Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )
       Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  ("Dave Dutcher", )
     Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Richard Huxton, )
   Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Alvaro Herrera, )
    Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )
     Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Alvaro Herrera, )
      Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )
       Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Tom Lane, )
        Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )

Hello,


I have upgraded from 7.3.9 to 8.2.3 and now the application that is
using Postgres is really slow.
Using pgfouine, I was able to identify a SQL select statement that was
running in 500 ms before and now that is running in more than 20 seconds !

The reason is that the execution plan is different from the 2 versions.
The difference is the order the tables are joined :

For 8.2.3 :
Seq Scan on lm05_t_tarif_panneau g (cost=0.00..2977.08 rows=18947
width=43) (actual time=0.006..65.388 rows=4062 loops=280)

For 7.3.9 :
Seq Scan on lm05_t_tarif_panneau g  (cost=0.00..90.00 rows=692
width=190) (actual time=0.03..206.23 rows=4062 loops=1)

Is there an option in the 8.2.3 to change in order to have the same
execution plan than before ?
I have compared the 2 postgresql.conf files and there are no differences
as far as I know.

Thanks for your help.

Best Regards,
Vincent Moreau


For 7.3.9 :

Unique  (cost=232.48..232.51 rows=1 width=497) (actual
time=524.49..543.00 rows=140 loops=1)
....

                                                  ->  Seq Scan on
lm05_t_tarif_panneau g  (cost=0.00..90.00 rows=692 width=190) (actual
time=0.03..206.23 rows=4062 loops=1)
                                                        Filter:
(((lrg_min < 1000) AND (lrg_max >= 1000)) OR ((lrg_min < 500) AND
(lrg_max >= 500)) OR (((
lrg_min)::numeric < 333.333333333333) AND ((lrg_max)::numeric >=
333.333333333333)) OR ((lrg_min < 250) AND (lrg_max >= 250)) OR
((lrg_min < 200) AND (lrg_
max >= 200)) OR (((lrg_min)::numeric < 166.666666666667) AND
((lrg_max)::numeric >= 166.666666666667)) OR (((lrg_min)::numeric <
142.857142857143) AND ((lr
g_max)::numeric >= 142.857142857143)) OR ((lrg_min < 125) AND (lrg_max
 >= 125)) OR (((lrg_min)::numeric < 111.111111111111) AND
((lrg_max)::numeric >= 111.
111111111111)) OR ((lrg_min < 100) AND (lrg_max >= 100)))
                                                  ->  Hash
(cost=32.35..32.35 rows=1 width=8) (actual time=19.07..19.07 rows=0
loops=1)
                                                        ->  Nested Loop
(cost=0.00..32.35 rows=1 width=8) (actual time=17.99..19.07 rows=1 loops=1)
                                                              ->  Seq
Scan on cm_gestion_modele_ca h  (cost=0.00..27.50 rows=1 width=4)
(actual time=0.09..17.35 rows=165 loops=1)

Filter: ((idmagasin = '011'::character varying) AND (idoav =
'PC_PLACARD'::character varying) AND (autorise = 1))
                                                              ->  Index
Scan using lm05_t_modele_cod_modele_key on lm05_t_modele a
(cost=0.00..4.83 rows=1 width=4) (actual time=0.01..0.01 rows=0 loops=165)

Index Cond: ("outer".cod_modele = a.cod_modele)

Filter: ((cod_type_ouverture = 'OUV_COU'::character varying) AND
(cod_type_panneau = 'PAN_MEL'::character varying) AND (cod_fournisseur =
5132) AND (cod_gamme_prof = 'Design Xtra'::character varying))




For 8.2.3 :

Unique (cost=5278.93..5278.95 rows=1 width=32) (actual
time=27769.435..27771.863 rows=140 loops=1)

...

-> Hash Join (cost=6.31..3055.59 rows=115 width=47) (actual
time=58.096..67.787 rows=48 loops=280)

Hash Cond: (g.cod_modele = a.cod_modele)

-> Seq Scan on lm05_t_tarif_panneau g (cost=0.00..2977.08 rows=18947
width=43) (actual time=0.006..65.388 rows=4062 loops=280)

Filter: (((lrg_min < 1000) AND (lrg_max >= 1000)) OR ((lrg_min < 500)
AND (lrg_max >= 500)) OR (((lrg_min)::numeric < 333.333333333333) AND
((lrg_max)::numeric >= 333.333333333333)) OR ((lrg_min < 250) AND
(lrg_max >= 250)) OR ((lrg_min < 200) AND (lrg_max >= 200)) OR
(((lrg_min)::numeric < 166.666666666667) AND ((lrg_max)::numeric >=
166.666666666667)) OR (((lrg_min)::numeric < 142.857142857143) AND
((lrg_max)::numeric >= 142.857142857143)) OR ((lrg_min < 125) AND
(lrg_max >= 125)) OR (((lrg_min)::numeric < 111.111111111111) AND
((lrg_max)::numeric >= 111.111111111111)) OR ((lrg_min < 100) AND
(lrg_max >= 100)))

-> Hash (cost=6.30..6.30 rows=1 width=4) (actual time=0.135..0.135
rows=1 loops=1)

-> Seq Scan on lm05_t_modele a (cost=0.00..6.30 rows=1 width=4) (actual
time=0.053..0.124 rows=1 loops=1)

Filter: (((cod_type_ouverture)::text = 'OUV_COU'::text) AND
((cod_type_panneau)::text = 'PAN_MEL'::text) AND (cod_fournisseur =
5132) AND ((cod_gamme_prof)::text = 'Design Xtra'::text))

-> Seq Scan on mag_gestion_modele_mag i (cost=0.00..8.78 rows=165
width=4) (actual time=0.053..0.214 rows=165 loops=1120)

Filter: (((idmagasin)::text = '011'::text) AND ((idoav)::text =
'PC_PLACARD'::text) AND (selection = 1))



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Subject: Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3
From: "Dave Dutcher"
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Subject: Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3