> They will generate a comparable amount of garbage, but I think updating the
> existing records is better than delete + insert, especially if there are also
> foreign key references to those records.

I don't think so.

Unless you are updating every column in the row, the UPDATE will generate a smaller disk footprint, as the new record version will only include the updated fields -- not a full copy of the row.

Then there is the impact on index structures that Vlad has pointed out.


From a performance point of view, it would be *much faster*, if you are able to:
- disable all indexes for the target table,
- delete all rows,
- import new rows and
- reactivate all indexes for the target table

This would likely require that you have near-exclusive access/use of the target table.


Sean