During btvacuumscan(), we lock the index for extension and then wait to acquire a cleanup lock on the last page. Then loop until we find a point where the index has not expanded again during our wait for lock on that last page. On a busy index this can take some time, especially when people regularly access data with the highest values in the index.
The comments there say "It is critical that we visit all leaf pages, including ones added after we start the scan, else we might fail to delete some deletable tuples." What seems strange is that we make no attempt to check whether we have already identified all tuples being removed by the VACUUM. We have the number of dead tuples we are looking for and we track the number of tuples we have deleted from the index, so we could easily make this check early and avoid waiting. Can we avoid scanning all pages once we have proven we have all dead tuples? -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
