Differences when calling query inside and outside cursor

Hi,

We're facing a weird performance problem in one of our PostgreSQL servers
running 8.0.26.

What can explain the difference between calling same query inside and
outside a cursor? If we run the query outside a cursor we got a response
time of 755ms and 33454ms if we call the same query inside a cursor.

I suspect the query called inside the cursor is using a different plan than
the same query outside a cursor. Is there a way to confirm this suspicion?


Query called outside a cursor:
pgipm=3D# explain analyze SELECT XMAX, ANO, MES, CODFUNC, SEQFUNC, TIPOPGTO=
,
CODPD, HRSPD, VLRPD, MESANO, TIPOCALCFERIAS, VLRBASE FROM fparq.cadpag
where  (ANO >'2013')  or (ANO =3D'2013'  and MES >'01')  or (ANO =3D'2013' =
 and
MES =3D'01'  and CODFUNC >'0000029602')  or (ANO =3D'2013'  and MES =3D'01'=
  and
CODFUNC =3D'0000029602'  and SEQFUNC >'02')  or (ANO =3D'2013'  and MES =3D=
'01'
and CODFUNC =3D'0000029602'  and SEQFUNC =3D'02'  and TIPOPGTO >   (' '))  =
or
(ANO =3D'2013'  and MES =3D'01'  and CODFUNC =3D'0000029602'  and SEQFUNC =
=3D'02'
and TIPOPGTO =3D (' ')  and CODPD >'000')  order by  ANO ASC,  MES ASC,
CODFUNC ASC,  SEQFUNC ASC,  TIPOPGTO ASC,  CODPD ASC;

QUERY
PLAN

---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
------
 Sort  (cost=3D151845.90..152304.21 rows=3D183322 width=3D62) (actual
time=3D706.676..728.080 rows=3D32828 loops=3D1)
   Sort Key: ano, mes, codfunc, seqfunc, tipopgto, codpd
   ->  Index Scan using pagpk_aux_mes, pagpk_aux_mes, pk_cadpag, pk_cadpag,
pk_cadpag, pagchavefunc00 on cadpag  (cost=3D0.00..131521.88 rows=3D183322
width=3D62) (actual time=3D0.664..614.080 rows=3D32828 loops=3D1)
         Index Cond: ((ano > 2013::smallint) OR ((ano =3D 2013::smallint) A=
ND
(mes > 1::smallint)) OR ((ano =3D 2013::smallint) AND (mes =3D 1::smallint)=
 AND
(codfunc > 29602::bigint)) OR ((ano =3D 2013::smallint) AND (mes =3D
1::smallint) AND (codfunc =3D 29602::bigint) AND (seqfunc > 2::smallint)) O=
R
((ano =3D 2013::smallint) AND (mes =3D 1::smallint) AND (codfunc =3D
29602::bigint) AND (seqfunc =3D 2::smallint) AND ((tipopgto)::text > '
'::text)) OR ((codfunc =3D 29602::bigint) AND (seqfunc =3D 2::smallint) AND
((tipopgto)::text =3D ' '::text) AND (codpd > 0::smallint) AND (ano =3D
2013::smallint) AND (mes =3D 1::smallint)))
         Filter: ((ano > 2013::smallint) OR ((ano =3D 2013::smallint) AND
(mes > 1::smallint)) OR ((ano =3D 2013::smallint) AND (mes =3D 1::smallint)=
 AND
(codfunc > 29602::bigint)) OR ((ano =3D 2013::smallint) AND (mes =3D
1::smallint) AND (codfunc =3D 29602::bigint) AND (seqfunc > 2::smallint)) O=
R
((ano =3D 2013::smallint) AND (mes =3D 1::smallint) AND (codfunc =3D
29602::bigint) AND (seqfunc =3D 2::smallint) AND ((tipopgto)::text > '
'::text)) OR ((ano =3D 2013::smallint) AND (mes =3D 1::smallint) AND (codfu=
nc =3D
29602::bigint) AND (seqfunc =3D 2::smallint) AND ((tipopgto)::text =3D '
'::text) AND (codpd > 0::smallint)))
 Total runtime: 755.878 ms
(6 rows)
___________________________________________________________________________=
_____________________________________________________________________
Query called inside a cursor:
pgipm=3D# select current_time;
       timetz
--------------------
 10:51:39.747798-02
(1 row)

pgipm=3D# BEGIN WORK;
BEGIN
pgipm=3D# DECLARE CUR1 CURSOR FOR
pgipm-# SELECT XMAX, ANO, MES, CODFUNC, SEQFUNC, TIPOPGTO, CODPD, HRSPD,
VLRPD, MESANO, TIPOCALCFERIAS, VLRBASE FROM fparq.cadpag    where  (ANO
>'2013')  or (ANO =3D'2013'  and MES >'01')  or (ANO =3D'2013'  and MES =3D=
'01'
and CODFUNC >'0000029602')  or (ANO =3D'2013'  and MES =3D'01'  and CODFUNC
=3D'0000029602'  and SEQFUNC >'02')  or (ANO =3D'2013'  and MES =3D'01'  an=
d
CODFUNC =3D'0000029602'  and SEQFUNC =3D'02'  and TIPOPGTO >   (' '))  or (=
ANO
=3D'2013'  and MES =3D'01'  and CODFUNC =3D'0000029602'  and SEQFUNC =3D'02=
'  and
TIPOPGTO =3D (' ')  and CODPD >'000')  order by  ANO ASC,  MES ASC,  CODFUN=
C
ASC,  SEQFUNC ASC,  TIPOPGTO ASC,  CODPD ASC;
DECLARE CURSOR
pgipm=3D# FETCH FORWARD 2 FROM CUR1;
 xmax | ano  | mes | codfunc | seqfunc | tipopgto | codpd | hrspd  |
vlrpd  | mesano | tipocalcferias | vlrbase
------+------+-----+---------+---------+----------+-------+--------+-------=
--+--------+----------------+---------
    0 | 2013 |   1 |   29602 |       2 | R        |     0 | 220.00 |
1743.28 |  12013 |                |    0.00
    0 | 2013 |   1 |   29602 |       2 | R        |    53 |  14.67 |
116.22 |  12013 |                |    0.00
(2 rows)

pgipm=3D# select current_time;
       timetz
--------------------
 10:51:39.748351-02
(1 row)

pgipm=3D# rollback;
ROLLBACK
pgipm=3D# select current_time;
       timetz
--------------------
 10:52:13.202640-02
(1 row)

pgipm=3D#

Thank you!

Reimer