> > However, for small operations it's a net loss - you avoid writing a WAL > record, but you have to fsync() the heap instead. If you only modify a few > rows, the extra fsync (or fsyncs if there are indexes too) is more expensive > than writing the WAL. > > We'd need a heuristic to decide whether to write WAL or fsync at the end. > For regular INSERTs, UPDATEs and DELETEs, you have the planner's estimate of > number of rows affected. Another thing we should do is move the fsync call > from the end of COPY (and other such operations) to the end of transaction. > That way if you do e.g one COPY followed by a bunch of smaller INSERTs or > UPDATEs, you only need to fsync the files once.
Have you thought about recovery, especially when the page size is greater than the disk block size( > 4K ). With WAL, there is a way to restore the pages to the original state, during recovery, if there are partial page writes. Is it possible to do the same with direct fsync without WAL? Gokul.
