In a comment I read
Just as a side note, it\'s sometimes faster to drop the indices of your table and recreate them after the bulk insert operation.
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One thing you should consider when dropping and recreating indexes is that it should only be done on automated processes that run during the low volumne periods of database use. While the index is dropped it can't be used for other queries that other users might be riunning at the same time. If you do this during production hours ,your users will probably start complaining of timeouts.