COPY invokes all the same logic as INSERT on the server side (rowexclusive locking, transaction log, updating indexes, rules). The difference is that all the rows are inserted as a single transaction. This reduces the number of fsync's on the xlog, which may be a limiting factor for you. You'll want to crank WAL_BUFFERS and CHECKPOINT_SEGMENTS to match, though. One of my streams has 6K records; I run with WB=1000, CS=128.
So what's the difference between a COPY and a batch of INSERT statements. Also, surely, fsyncs only occur at the end of a transaction, no need to fsync before a commit has been issued, right?
I think COPY also has the advantage that for index updates it only grabs the lock once, rather than grabbing and releasing for each row. But I believe you are right that fsync only happens on COMMIT.
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