Re: COPY FROM - to avoid WAL generation

On 8/21/18 9:00 AM, Ravi Krishna wrote:

> In a recent thread of mine I learned something very interesting. If a 
> table is created and data is loaded via COPY FROM within the same 
> transaction, then PG will be smart enough to not generate WAL logs 
> because all it needs to do is to track the status of the transaction 
> and let the data load go to the new data file created for the table.  
> If committed, the table is released for other sessions, if rolledback, 
> vaccum will delete the data file later on.
>
> I tested it as follows for a table with 50 milllion rows. No indexes.
>
> Case 1
>   - create the table first.
>   - in a separate transaction load the 50 million rows.
>
> Took 3 min 22 seconds
>
> Case 2
>   - start transaction
>   - create table
>   - load 50 million rows
>   - commit transaction
>
> Took: 3 min 16 seconds.
>
> Am I missing anything?
>
Have you looked into pg_bulkload?

https://github.com/ossc-db/pg_bulkload

Docs are here:

http://ossc-db.github.io/pg_bulkload/index.html

Jeff