Re: Slowdown problem when writing 1.7million records

43 hours? Ouch, that is quite a long time! I'm no expert by any means, but
here are a few tips that I've picked up on this list that might help out:

1. The COPY command is blazing fast for importing, if you are certain your
input is clean, this is the way to go. Read more about that here:
http://www.postgresql.org/users-lounge/docs/7.0/postgres/sql-copy.htm
2. If you have any indexes, drop them, then do your import, then readd them
after that is complete. Indexes slow inserts down quite a bit.
3. If you are using INSERTs (I can't see a COPY taking more than a few
minutes), make sure that you are wrapping them in an explicit transaction.
Otherwise, each INSERT becomes its own transaction with all that overhead.
4. If you *are* using transactions, break the transactions up into chunks.
Trying to maintain a single transaction over 1.7 million INSERTs will slow
things down. Personally I'd probably go with about 500 at a time.

I'm sure someone else will have another suggestion or three...

Greg

----- Original Message -----
From: "Stephen Livesey" <ste@exact3ex.co.uk>
To: <pgsql-general@postgresql.org>
Sent: Tuesday, February 27, 2001 4:44 AM
Subject: Slowdown problem when writing 1.7million records


> I am very new to PostgreSQL and have installed v7.03 on a Red Hat Linux
> Server (v6.2), I am accessing the files using JDBC from a Windows 2000 PC.
>
> I have created a small file as follows:
> CREATE TABLE expafh (
> postcode CHAR(8) NOT NULL,
> postcode_record_no INT,
> street_name CHAR(30),
> town CHAR(31),
> PRIMARY KEY(postcode) )
>
> I am now writing 1.7million records to this file.
>
> The first 100,000 records took 15mins.
> The next 100,000 records took 30mins
> The last 100,000 records took 4hours.
>
> In total, it took 43 hours to write 1.7million records.
>
> Is this sort of degradation normal using a PostgreSQL database?
>
> I have never experienced this sort of degradation with any other database
> and I have done exactly the same test (using the same hardware) on the
> following databases:
>     DB2 v7 in total took 10hours 6mins
>     Oracle 8i in total took 3hours 20mins
>     Interbase v6 in total took 1hr 41min
>     MySQL v3.23 in total took 54mins
>
>
> Any Help or advise would be appreciated.
>
> Thanks
> Stephen Livesey
>
>
>
>