Обсуждение: Improving SQL performance

Reimer

Carlos H. Reimer wrote:
> Hi,
>
> I know that the problem with the following SQL is the "LOG.CODCEP =
> ENDE.CODCEP||CODLOG" condition, but what can I
> do to improve the performance?
>
I wouldn't say it's the join condition.  There is a nested loop join on
500k+ rows.
Is it possible to put an index on LOG.CODCEP?

That might give you a better plan, as you only have 1 row in the left of
the join.  so index scan would be preferable.

Regards

Russell Smith
> Is there a type of index that could help or is there another way to
> build this SQL?
>
> Thank you in advance!
>
> explain analyze
> SELECT ENDE.* , DEND.DESEND, DEND.USOEND, DEND.DUPEND,
>                to_char('F') as NOVO,
>                LOG.TIPLOG
>           FROM TT_END ENDE LEFT OUTER JOIN TD_END DEND ON DEND.CODTAB
> = ENDE.TIPEND
>                            LEFT OUTER JOIN TT_LOG LOG ON LOG.CODCEP =
> ENDE.CODCEP||CODLOG
>          WHERE ENDE.FILCLI = '001'
>            AND ENDE.CODCLI = ' 19475';
>
>
>                                                             QUERY
> PLAN
>
----------------------------------------------------------------------------------------------------------------------------------
>  Nested Loop Left Join  (cost=0.00..25366.84 rows=1259 width=417)
> (actual time=1901.499..1901.529 rows=1 loops=1)
>    Join Filter: (("inner".codcep)::text = (("outer".codcep)::text ||
> ("outer".codlog)::text))
>    ->  Nested Loop Left Join  (cost=0.00..4.91 rows=1 width=412)
> (actual time=0.117..0.144 rows=1 loops=1)
>          Join Filter: ("inner".codtab = "outer".tipend)
>          ->  Index Scan using pk_end on tt_end ende  (cost=0.00..3.87
> rows=1 width=388) (actual time=0.066..0.078 rows=1 loops=1)
>                Index Cond: ((filcli = '001'::bpchar) AND (codcli = '
> 19475'::bpchar))
>          ->  Seq Scan on td_end dend  (cost=0.00..1.02 rows=2
> width=33) (actual time=0.012..0.018 rows=2 loops=1)
>    ->  Seq Scan on tt_log log  (cost=0.00..12254.24 rows=582424
> width=17) (actual time=0.013..582.521 rows=582424 loops=1)
>  Total runtime: 1901.769 ms
> (9 rows)
>
> \d tt_log
>             Table "TOTALL.tt_log"
>  Column |          Type          | Modifiers
> --------+------------------------+-----------
>  codbai | numeric(5,0)           | not null
>  nomlog | character varying(55)  | not null
>  codcep | character(8)           | not null
>
> \d tt_end
>                           Table "TOTALL.tt_end"
>  Column |         Type          |                Modifiers
> --------+-----------------------+-----------------------------------------
> ...
> ...
> ...
>  codlog | character(3)          |
> ...
> ...
> ...
>  codcep | character(5)          |
> ...
> ...
>
> Reimer
>
>

"Carlos H. Reimer" <carlos.reimer@opendb.com.br> writes:
> I know that the problem with the following SQL is the "LOG.CODCEP =
> ENDE.CODCEP||CODLOG" condition, but what can I
> do to improve the performance?

Seems the problem is not using an index for tt_log.  Do you have an
index on tt_log.codcep?  If so, maybe you need to cast the result of
the concatenation to char(8) to get it to use the index.

            regards, tom lane

Yes, I do have an index on tt_log.codcep.

Indexes I´ve on both tables:

tt_end
Indexes:
    "pk_end" PRIMARY KEY, btree (filcli, codcli, codfil, numend)
    "ak_end_numdoc" UNIQUE, btree (numdoc)
    "i_fk_end_darc" btree (codarc, tiparc)
    "i_fk_end_dend" btree (tipend)
    "i_fk_end_dfil" btree (codfil)
    "i_fk_end_dreg" btree (regiao)
    "i_fk_end_mun" btree (codcid)
tt_log
Indexes:
    "i_fk_log_bai" btree (codbai)
    "i_lc_log_codcep" btree (codcep)

Any clue?

Thanks!

Reimer


> -----Mensagem original-----
> De: Tom Lane [mailto:tgl@sss.pgh.pa.us]
> Enviada em: quinta-feira, 11 de janeiro de 2007 16:31
> Para: carlos.reimer@opendb.com.br
> Cc: pgsql-performance@postgresql.org
> Assunto: Re: [PERFORM] Improving SQL performance
>
>
> "Carlos H. Reimer" <carlos.reimer@opendb.com.br> writes:
> > I know that the problem with the following SQL is the "LOG.CODCEP =
> > ENDE.CODCEP||CODLOG" condition, but what can I
> > do to improve the performance?
>
> Seems the problem is not using an index for tt_log.  Do you have an
> index on tt_log.codcep?  If so, maybe you need to cast the result of
> the concatenation to char(8) to get it to use the index.
>
>             regards, tom lane
>
>

Hi, Carlos,

Wouldn't it be better if you used INT in 'codcep' in both tables (as
CEP/ZIP numbers are [0-9]{8})? Casting as Tom Lane suggested is also a
good alternative, yet I think it'd be much better if you used int in
both columns.

Regards,
Cesar

Let's see the query:

SELECT ENDE.* , DEND.DESEND, DEND.USOEND, DEND.DUPEND,
               to_char('F') as NOVO,
               LOG.TIPLOG
          FROM TT_END ENDE LEFT OUTER JOIN TD_END DEND ON DEND.CODTAB =
ENDE.TIPEND
                           LEFT OUTER JOIN TT_LOG LOG ON LOG.CODCEP =
ENDE.CODCEP||CODLOG
         WHERE ENDE.FILCLI = '001'
           AND ENDE.CODCLI = ' 19475';




Carlos H. Reimer wrote:
> Yes, I do have an index on tt_log.codcep.
>
> Indexes I´ve on both tables:
>
> tt_end
> Indexes:
>     "pk_end" PRIMARY KEY, btree (filcli, codcli, codfil, numend)
>     "ak_end_numdoc" UNIQUE, btree (numdoc)
>     "i_fk_end_darc" btree (codarc, tiparc)
>     "i_fk_end_dend" btree (tipend)
>     "i_fk_end_dfil" btree (codfil)
>     "i_fk_end_dreg" btree (regiao)
>     "i_fk_end_mun" btree (codcid)
> tt_log
> Indexes:
>     "i_fk_log_bai" btree (codbai)
>     "i_lc_log_codcep" btree (codcep)
>
> Any clue?
>
> Thanks!
>
> Reimer
>
>
>
>> -----Mensagem original-----
>> De: Tom Lane [mailto:tgl@sss.pgh.pa.us]
>> Enviada em: quinta-feira, 11 de janeiro de 2007 16:31
>> Para: carlos.reimer@opendb.com.br
>> Cc: pgsql-performance@postgresql.org
>> Assunto: Re: [PERFORM] Improving SQL performance
>>
>>
>> "Carlos H. Reimer" <carlos.reimer@opendb.com.br> writes:
>>
>>> I know that the problem with the following SQL is the "LOG.CODCEP =
>>> ENDE.CODCEP||CODLOG" condition, but what can I
>>> do to improve the performance?
>>>
>> Seems the problem is not using an index for tt_log.  Do you have an
>> index on tt_log.codcep?  If so, maybe you need to cast the result of
>> the concatenation to char(8) to get it to use the index.
>>
>>             regards, tom lane
>>
>>
>>
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 6: explain analyze is your friend
>
>

Yes, casting the result improved the time response a lot.

Thank you!

Reimer



> -----Mensagem original-----
> De: pgsql-performance-owner@postgresql.org
> [mailto:pgsql-performance-owner@postgresql.org]Em nome de Tom Lane
> Enviada em: quinta-feira, 11 de janeiro de 2007 16:31
> Para: carlos.reimer@opendb.com.br
> Cc: pgsql-performance@postgresql.org
> Assunto: Re: [PERFORM] Improving SQL performance
>
>
> "Carlos H. Reimer" <carlos.reimer@opendb.com.br> writes:
> > I know that the problem with the following SQL is the "LOG.CODCEP =
> > ENDE.CODCEP||CODLOG" condition, but what can I
> > do to improve the performance?
>
> Seems the problem is not using an index for tt_log.  Do you have an
> index on tt_log.codcep?  If so, maybe you need to cast the result of
> the concatenation to char(8) to get it to use the index.
>
>             regards, tom lane
>
> ---------------------------(end of broadcast)---------------------------
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