When doing database work over the web, especially when many records are on one page, *many* updates get posted to pg that do not change the record. Eg, the page may contain 50 records, the user changes 1, and submits.
I assume that a no-change update takes the same resources as a "real" update, ie, a new block is allocated to write the record, the record written, indicies are rerouted to the new block, and the old block needs to be vacuumed later. Is this true? In SQL, the only way I know to prevent this thrashing is to write the update with an elaborate where clause, eg, "update ... where pk=1 and (c1!='v1' or c2!='v2' or ... )". This adds cost both to the app server and to pg - is the cost justified? Finally, is there anyway to flag pg to ignore no-change updates? This seems to me to me the most efficient way of handling the needless work. thanks chester __________________________________________________ Do you Yahoo!? HotJobs - Search new jobs daily now http://hotjobs.yahoo.com/ ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
