maintenence_work_mem to help vacuuming
24 Aug 2014
Jeff Janes posted this to the PostgreSQL general maling list, and I did not want to forget it:
"Vacuum can only memorize one dead tuple for every 6 bytes of maintenance_work_mem. If there are more dead tuples than that, it needs to make multiple passes over the indexes.
"Increase maintenance_work_mem to improve the efficiency."