Re: Differences when calling query inside and outside cursor

Hi,

As we suspected the SELECT inside a cursor is using a different plan than
outside a cursor:

pgipm=# explain analyze 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 ='2013' and MES >'01') or (ANO ='2013' and MES ='01'
and CODFUNC >'0000029602') or (ANO ='2013' and MES ='01' and CODFUNC
='0000029602' and SEQFUNC >'02') or (ANO ='2013' and MES ='01' and
CODFUNC ='0000029602' and SEQFUNC ='02' and TIPOPGTO > (' ')) or (ANO
='2013' and MES ='01' and CODFUNC ='0000029602' and SEQFUNC ='02' and
TIPOPGTO = (' ') and CODPD >'000') order by ANO ASC, MES ASC, CODFUNC
ASC, SEQFUNC ASC, TIPOPGTO ASC, CODPD ASC;

QUERY PLAN

------------------------------------------------------------
------------------------------------------------------------
------------------------------------------------------------
------------------------------------------------------------
------------------------------------------------------------
------------------------------------------------------------
------------------------------------------------------------
------------------------------------------------------------
------------------------------------------------------------
--------------------------------------------------------
Index Scan using pk_cadpag on cadpag (cost=0.00..383580.89 rows=183326
width=62)
Filter: ((ano > 2013::smallint) OR ((ano = 2013::smallint) AND (mes >
1::smallint)) OR ((ano = 2013::smallint) AND (mes = 1::smallint) AND
(codfunc > 29602::bigint)) OR ((ano = 2013::smallint) AND (mes =
1::smallint) AND (codfunc = 29602::bigint) AND (seqfunc > 2::smallint)) OR
((ano = 2013::smallint) AND (mes = 1::smallint) AND (codfunc =
29602::bigint) AND (seqfunc = 2::smallint) AND ((tipopgto)::text > '
'::text)) OR ((ano = 2013::smallint) AND (mes = 1::smallint) AND (codfunc =
29602::bigint) AND (seqfunc = 2::smallint) AND ((tipopgto)::text = '
'::text) AND (codpd > 0::smallint)))
(2 rows)

Should it not be the same inside or outside a cursor?

Thank you in advance!

On Wed, Feb 13, 2013 at 11:21 AM, Carlos Henrique Reimer <
carlos(dot)reimer(at)opendb(dot)com(dot)br> wrote:

> 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=# explain analyze SELECT XMAX, ANO, MES, CODFUNC, SEQFUNC, TIPOPGTO,
> CODPD, HRSPD, VLRPD, MESANO, TIPOCALCFERIAS, VLRBASE FROM fparq.cadpag
> where (ANO >'2013') or (ANO ='2013' and MES >'01') or (ANO ='2013' and
> MES ='01' and CODFUNC >'0000029602') or (ANO ='2013' and MES ='01' and
> CODFUNC ='0000029602' and SEQFUNC >'02') or (ANO ='2013' and MES ='01'
> and CODFUNC ='0000029602' and SEQFUNC ='02' and TIPOPGTO > (' ')) or
> (ANO ='2013' and MES ='01' and CODFUNC ='0000029602' and SEQFUNC ='02'
> and TIPOPGTO = (' ') and CODPD >'000') order by ANO ASC, MES ASC,
> CODFUNC ASC, SEQFUNC ASC, TIPOPGTO ASC, CODPD ASC;
>
> QUERY
> PLAN
>
>
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> Sort (cost=151845.90..152304.21 rows=183322 width=62) (actual
> time=706.676..728.080 rows=32828 loops=1)
> 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=0.00..131521.88
> rows=183322 width=62) (actual time=0.664..614.080 rows=32828 loops=1)
> Index Cond: ((ano > 2013::smallint) OR ((ano = 2013::smallint)
> AND (mes > 1::smallint)) OR ((ano = 2013::smallint) AND (mes = 1::smallint)
> AND (codfunc > 29602::bigint)) OR ((ano = 2013::smallint) AND (mes =
> 1::smallint) AND (codfunc = 29602::bigint) AND (seqfunc > 2::smallint)) OR
> ((ano = 2013::smallint) AND (mes = 1::smallint) AND (codfunc =
> 29602::bigint) AND (seqfunc = 2::smallint) AND ((tipopgto)::text > '
> '::text)) OR ((codfunc = 29602::bigint) AND (seqfunc = 2::smallint) AND
> ((tipopgto)::text = ' '::text) AND (codpd > 0::smallint) AND (ano =
> 2013::smallint) AND (mes = 1::smallint)))
> Filter: ((ano > 2013::smallint) OR ((ano = 2013::smallint) AND
> (mes > 1::smallint)) OR ((ano = 2013::smallint) AND (mes = 1::smallint) AND
> (codfunc > 29602::bigint)) OR ((ano = 2013::smallint) AND (mes =
> 1::smallint) AND (codfunc = 29602::bigint) AND (seqfunc > 2::smallint)) OR
> ((ano = 2013::smallint) AND (mes = 1::smallint) AND (codfunc =
> 29602::bigint) AND (seqfunc = 2::smallint) AND ((tipopgto)::text > '
> '::text)) OR ((ano = 2013::smallint) AND (mes = 1::smallint) AND (codfunc =
> 29602::bigint) AND (seqfunc = 2::smallint) AND ((tipopgto)::text = '
> '::text) AND (codpd > 0::smallint)))
> Total runtime: 755.878 ms
> (6 rows)
>
> ________________________________________________________________________________________________________________________________________________
> Query called inside a cursor:
> pgipm=# select current_time;
> timetz
> --------------------
> 10:51:39.747798-02
> (1 row)
>
> pgipm=# BEGIN WORK;
> BEGIN
> pgipm=# 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 ='2013' and MES >'01') or (ANO ='2013' and MES ='01'
> and CODFUNC >'0000029602') or (ANO ='2013' and MES ='01' and CODFUNC
> ='0000029602' and SEQFUNC >'02') or (ANO ='2013' and MES ='01' and
> CODFUNC ='0000029602' and SEQFUNC ='02' and TIPOPGTO > (' ')) or (ANO
> ='2013' and MES ='01' and CODFUNC ='0000029602' and SEQFUNC ='02' and
> TIPOPGTO = (' ') and CODPD >'000') order by ANO ASC, MES ASC, CODFUNC
> ASC, SEQFUNC ASC, TIPOPGTO ASC, CODPD ASC;
> DECLARE CURSOR
> pgipm=# 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=# select current_time;
> timetz
> --------------------
> 10:51:39.748351-02
> (1 row)
>
> pgipm=# rollback;
> ROLLBACK
> pgipm=# select current_time;
> timetz
> --------------------
> 10:52:13.202640-02
> (1 row)
>
> pgipm=#
>
> Thank you!
>
> Reimer
>
>

--
Reimer
47-3347-1724 47-9183-0547 msn: carlos(dot)reimer(at)opendb(dot)com(dot)br