2015-07-24 Nicolas Barbier <nicolas.barb...@gmail.com>: > Especially useful would be to know whether interleaving a small number > of TID ordered streams (as would probably be generated by parallel > scans/processing) would result in an ordering that performs > significantly worse or not. I assume (but cannot prove) that in this > case the OS will understand the read pattern as being multiple streams > and prefetching will work correctly.
OTOH, that is probably only true when there are a large number of duplicate keys. Otherwise the order within each (small) group will appear random, which may or may not result in a significant performance drop. This probably also depends on whether fadvise (or friends) are used. Nicolas -- A. Because it breaks the logical sequence of discussion. Q. Why is top posting bad? -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
