TJ O'Donnell wrote: > > If I have two threads modifying the same "bit" field: > > thread1=> update table set bf=bf | '01000' > > thread2=> update table set bf=bf | '10000' > > Will this operation always be safe (e.g. result in bf='11000')? Or > > Won't this always result in bf='11xxx', depending on the > original values of bf?
Not even. Consider: thread1=> update table set bf=bf | '01000' thread3=> update table set bf=bf & '10111' thread2=> update table set bf=bf | '10000' Now you get bf=10xxx. They're thread safe in that all transformations will be applied as-if serially, so no bit sets or unsets will be lost, but you can't guarantee that another client won't interfere with the results. ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
