On Sat, Mar 10, 2018 at 6:37 AM, Robert Haas <robertmh...@gmail.com> wrote: > On Mon, Jan 15, 2018 at 11:35 AM, David Fetter <da...@fetter.org> wrote: >> - We follow the SQL standard and make SERIALIZABLE the default >> transaction isolation level, and > > The consequences of such a decision would include: > > - pgbench -S would run up to 10x slower, at least if these old > benchmark results are still valid: > > https://www.postgresql.org/message-id/ca+tgmozog1wfbyrqzjukilsxw5sdujjguey0c2bqsg-tcis...@mail.gmail.com > > - pgbench without -S would fail outright, because it doesn't have > provision to retry failed transactions. > > https://commitfest.postgresql.org/16/1419/ > > - Many user applications would probably also experience similar difficulties. > > - Parallel query would no longer work by default, unless this patch > gets committed: > > https://commitfest.postgresql.org/17/1004/ > > I think a good deal of work to improve the performance of serializable > would need to be done before we could even think about making it the > default -- and even then, the fact that it really requires the > application to be retry-capable seems like a pretty major obstacle.
Also: - It's not available on hot standbys. Experimental patches have been developed based on the read only safe snapshot concept, but some tricky problems remain unsolved. - Performance is terrible (conflicts are maximised) if you use any index type except btree, unless some of these get committed: https://commitfest.postgresql.org/17/1172/ https://commitfest.postgresql.org/17/1183/ https://commitfest.postgresql.org/17/1466/ -- Thomas Munro http://www.enterprisedb.com
