I did not checked myself but if postgres does snaphost isolation as indicated in wikipedia - there should be no issue and then no lock is needed...
http://en.wikipedia.org/wiki/Isolation_%28database_systems%29
http://en.wikipedia.org/wiki/Snapshot_isolation
But sill probably my suggestion would be correct - for example this would avoid consistency issue when a user interaction spans multiple transactions - aka a wizard
I did not checked myself but if postgres does snaphost isolation as indicated in wikipedia - there should be no issue and then no lock is needed...
http:// en.wikipedia. org/wiki/ Isolation_ %28database_ systems% 29
http:// en.wikipedia. org/wiki/ Snapshot_ isolation
But sill probably my suggestion would be correct - for example this would avoid consistency issue when a user interaction spans multiple transactions - aka a wizard