Re: Insert performance

joël Winteregg wrote:
> Hi Richard,
>
>>> Here is my problem. With some heavy insert into a simple BD (one
>>> table, no indexes) i can't get better perf than 8000 inserts/sec. I'm
>>> testing it using a simple C software which use libpq and which use:
>>> - Insert prepared statement (to avoid too many request parsing on the
>>> server)
>>> - transaction of 100000 inserts
>> Are each of the INSERTs in their own transaction?
>>
>
> No, as said above transactions are made of 100000 inserts...

Hmm - I read that as just meaning "inserted 100000 rows". You might find
that smaller batches provide peak performance.

>> If so, you'll be limited by the speed of the disk the WAL is running on.
>>
>> That means you have two main options:
>> 1. Have multiple connections inserting simultaneously.
>
> Yes, you're right. That what i have been testing and what provide the
> best performance ! I saw that postgresql frontend was using a lot of CPU
> and not both of them (i'm using a pentium D, dual core). To the opposit,
> the postmaster process use not much resources. Using several client,
> both CPU are used and i saw an increase of performance (about 18000
> inserts/sec).
>
> So i think my bottle neck is more the CPU speed than the disk speed,
> what do you think ?

Well, I think it's fair to say it's not disk. Let's see - the original
figure was 8000 inserts/sec, which is 0.125ms per insert. That sounds
plausible to me for a round-trip to process a simple command - are you
running the client app on the same machine, or is it over the network?

Two other things to bear in mind:
1. If you're running 8.2 you can have multiple sets of values in an INSERT
http://www.postgresql.org/docs/8.2/static/sql-insert.html

2. You can do a COPY from libpq - is it really not possible?

--
   Richard Huxton
   Archonet Ltd