Loading methods

The preferred path to get a lot of data into the database is using the COPY command. This is the fastest way to insert a set of rows. If that's not practical, and you have to use INSERT instead, you should try to include as many records as possible per commit, wrapping several into a BEGIN/COMMIT block. Most applications find that between 100 and 1000 rows per commit gives the majority of the performance possible in doing batch inserts, but it's still not going to be as fast as COPY.

From slowest to fastest, this is the usual ranking:

1. INSERT a single record at once.
2. INSERT larger blocks of records at one time.
3. Use a single COPY at a time. This is what a standard pg_restore does.
4. Multiple INSERT processes using larger blocks in parallel.
5. Use multiple COPY commands at once. Parallel pg_restore does this.

Note that getting multiple processes doing insert or copy at once can be harder than expected in some programming languages. Process or threading limitations...