Re: Removing duplicate records from a bulk upload (rationale behind selecting a method)

John McKown wrote
> I don't
> know, myself, why this would be faster. But I'm not any kind of a
> PostgreSQL expert either.

It is faster because PostgreSQL does not have native parallelism.  By using
a%n in a where clause you can start n separate sessions and choose a
different value of n for each one and manually introduce parallelism into
the activity.

Though given this is going to likely be I/O constrained the possible gains
do not scale lineally with the number of sessions - which themselves
effectively max out at the number of cores available to the server.

David J.




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