Обсуждение: Insert performance with composite index

On Mon, Nov 1, 2010 at 14:49, Divakar Singh <dpsmails@yahoo.com> wrote:
> I am trying to tune my libpq program for insert performance.
> When I tried inserting 1M rows into a table with a Primary Key, it took
> almost 62 seconds.
> After adding a composite index of 2 columns, the performance degrades to 125
> seconds.

This sounds a lot like the bottleneck I was hitting. What Linux kernel
version are you running?

If it's 2.6.33 or later, see:
http://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server#wal_sync_method_wal_buffers
http://archives.postgresql.org/pgsql-performance/2010-10/msg00602.php

Regards,
Marti

On Mon, Nov 1, 2010 at 14:56, Divakar Singh <dpsmails@yahoo.com> wrote:
> Thanks for your tips. i will try those.
> I am on Solaris Sparc 5.10

Sorry, I assumed you were running Linux. But still it could be the
same problem as I had.

Be careful changing your wal_sync_method, as it has the potential to
corrupt your database. I have no experience with Solaris.

For what it's worth, Jignesh Shah recommends using
wal_sync_method=fsync on Solaris:
http://blogs.sun.com/jkshah/entry/postgresql_on_solaris_better_use
http://blogs.sun.com/jkshah/entry/postgresql_wal_sync_method_and

Regards,
Marti

2010/11/1 Divakar Singh <dpsmails@yahoo.com>:
> Hi,
> I am trying to tune my libpq program for insert performance.
> When I tried inserting 1M rows into a table with a Primary Key, it took
> almost 62 seconds.
> After adding a composite index of 2 columns, the performance degrades to 125
> seconds.
> I am using COPY to insert all data in 1 transaction.
>
> the table definition is
>
> CREATE TABLE ABC
> (
>   event integer,
>   innodeid character varying(80),
>   innodename character varying(80),
>   sourceid character varying(300),
>   intime timestamp(3) without time zone,
>   outnodeid character varying(80),
>   outnodename character varying(80),
>   destinationid character varying(300),
>   outtime timestamp(3) without time zone,
>   bytes integer,
>   cdrs integer,
>   tableindex integer NOT NULL,
>   noofsubfilesinfile integer,
>   recordsequenceintegerlist character varying(1000),
>   CONSTRAINT tableindex_pkey PRIMARY KEY (tableindex)
> )
>
> the index definition is
>
>
> CREATE INDEX "PK_AT2"
>   ON ABC
>   USING btree
>   (event, tableindex)
> TABLESPACE sample;

Indexing twice the same column is useless. (perhaps move your PK to
the tablespace 'sample' is good too ?)

>
> Any tip to increase the insert performance in this case?

If you create or truncate  table then copy to it, you should create
index after the copy order.

>
> It would also be helpful if someone can send comprehensive libpq programming
> guide for PG 9.x. Online doc of libpq is not much helpful for a newbie like
> me.
>
>
> Best Regards,
> Divakar
>
>



--
Cédric Villemain               2ndQuadrant
http://2ndQuadrant.fr/     PostgreSQL : Expertise, Formation et Support

Hi,

On Monday 01 November 2010 13:49:14 Divakar Singh wrote:
> When I tried inserting 1M rows into a table with a Primary Key, it took
> almost 62 seconds.
> After adding a composite index of 2 columns, the performance degrades to
> 125 seconds.
> I am using COPY to insert all data in 1 transaction.
Without seeing your config its hard to suggest anything here. Did you do basic
tuning of your pg installation?

wal_buffers, shared_buffers, checkpoint_segments, maintenance_work_mem are
likely most relevant for that specific case.

Andres

On Monday 01 November 2010 15:08:10 Divakar Singh wrote:
> here are my parameters:
Which pg version is that?

On Monday 01 November 2010 15:16:49 Divakar Singh wrote:
> I am using 9.0.1
Either thats not true or you cargo culted loads of your config from a
significantly older pg version.

Things like:

#bgwriter_delay = 200            # 10-10000 milliseconds between rounds
bgwriter_lru_percent = 0        # 0-100% of LRU buffers scanned/round
#bgwriter_lru_maxpages = 5        # 0-1000 buffers max written/round
#bgwriter_all_percent = 0.333        # 0-100% of all buffers scanned/round
bgwriter_all_maxpages = 0        # 0-1000 buffers max written/round

make me very suspicious.

As I said, I would check the variables I referenced in my first post...

Andres

On Monday 01 November 2010 15:28:19 Divakar Singh wrote:
> Do you mean these parameters have been removed starting 9.X?
> As I see on
> http://www.network-theory.co.uk/docs/postgresql/vol3/BackgroundWriter.html
> ,these parameters were added starting from 8.0 right?
No, I mean setting to 0 is a bit of a strange value in many situations.

And you have comments like:
#max_fsm_pages = 20000            # min max_fsm_relations*16, 6 bytes each
#max_fsm_relations = 1000        # min 100, ~70 bytes each

Which reference config options which do not exist anymore. And you have
shared_buffers = 81920
Which indicates that you started from 8.1/8.2 or so...

Andres

On Mon, Nov 01, 2010 at 02:57:56PM +0100, Cédric Villemain wrote:
> >   CONSTRAINT tableindex_pkey PRIMARY KEY (tableindex)
> > )
> > the index definition is
> > CREATE INDEX "PK_AT2"
> >   ON ABC
> >   USING btree
> >   (event, tableindex)
> > TABLESPACE sample;
>
> Indexing twice the same column is useless. (perhaps move your PK to
> the tablespace 'sample' is good too ?)

why do you say that?
these are not the same indexes and they serve different purposes.

Best regards,

depesz

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2010/11/2 hubert depesz lubaczewski <depesz@depesz.com>:
> On Mon, Nov 01, 2010 at 02:57:56PM +0100, Cédric Villemain wrote:
>> >   CONSTRAINT tableindex_pkey PRIMARY KEY (tableindex)
>> > )
>> > the index definition is
>> > CREATE INDEX "PK_AT2"
>> >   ON ABC
>> >   USING btree
>> >   (event, tableindex)
>> > TABLESPACE sample;
>>
>> Indexing twice the same column is useless. (perhaps move your PK to
>> the tablespace 'sample' is good too ?)
>
> why do you say that?
> these are not the same indexes and they serve different purposes.

Given that tableindex is the PK column, I really like to now the usage
pattern for having it indexed twice.

>
> Best regards,
>
> depesz
>
> --
> Linkedin: http://www.linkedin.com/in/depesz  /  blog: http://www.depesz.com/
> jid/gtalk: depesz@depesz.com / aim:depeszhdl / skype:depesz_hdl / gg:6749007
>



--
Cédric Villemain               2ndQuadrant
http://2ndQuadrant.fr/     PostgreSQL : Expertise, Formation et Support

On Tue, Nov 02, 2010 at 12:04:42PM +0100, Cédric Villemain wrote:
> 2010/11/2 hubert depesz lubaczewski <depesz@depesz.com>:
> > On Mon, Nov 01, 2010 at 02:57:56PM +0100, Cédric Villemain wrote:
> >> >   CONSTRAINT tableindex_pkey PRIMARY KEY (tableindex)
> >> > )
> >> > the index definition is
> >> > CREATE INDEX "PK_AT2"
> >> >   ON ABC
> >> >   USING btree
> >> >   (event, tableindex)
> >> > TABLESPACE sample;
> >>
> >> Indexing twice the same column is useless. (perhaps move your PK to
> >> the tablespace 'sample' is good too ?)
> >
> > why do you say that?
> > these are not the same indexes and they serve different purposes.
>
> Given that tableindex is the PK column, I really like to now the usage
> pattern for having it indexed twice.

select * from table where event = 123 order by tableindex desc limit 50;

Best regards,

depesz

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2010/11/2 hubert depesz lubaczewski <depesz@depesz.com>:
> On Tue, Nov 02, 2010 at 12:04:42PM +0100, Cédric Villemain wrote:
>> 2010/11/2 hubert depesz lubaczewski <depesz@depesz.com>:
>> > On Mon, Nov 01, 2010 at 02:57:56PM +0100, Cédric Villemain wrote:
>> >> >   CONSTRAINT tableindex_pkey PRIMARY KEY (tableindex)
>> >> > )
>> >> > the index definition is
>> >> > CREATE INDEX "PK_AT2"
>> >> >   ON ABC
>> >> >   USING btree
>> >> >   (event, tableindex)
>> >> > TABLESPACE sample;
>> >>
>> >> Indexing twice the same column is useless. (perhaps move your PK to
>> >> the tablespace 'sample' is good too ?)
>> >
>> > why do you say that?
>> > these are not the same indexes and they serve different purposes.
>>
>> Given that tableindex is the PK column, I really like to now the usage
>> pattern for having it indexed twice.
>
> select * from table where event = 123 order by tableindex desc limit 50;

Correct. Thanks Hubert.

--
Cédric Villemain               2ndQuadrant
http://2ndQuadrant.fr/     PostgreSQL : Expertise, Formation et Support