david@xxxxxxx writes: > however I really don't understand why it is more efficiant to have a 5B > line table that you do a report/query against 0.1% of then it is to have > 1000 different tables of 5M lines each and do a report/query against 100% > of. Essentially what you are doing when you do that is taking the top few levels of the index out of the database and putting it into the filesystem; plus creating duplicative indexing information in the database's system catalogs. The degree to which this is a win is *highly* debatable, and certainly depends on a whole lot of assumptions about filesystem performance. You also need to assume that constraint-exclusion in the planner is pretty doggone cheap relative to the table searches, which means it almost certainly will lose badly if you carry the subdivision out to the extent that the individual tables become small. (This last could be improved in some cases if we had a more explicit representation of partitioning, but it'll never be as cheap as one more level of index search.) I think the main argument for partitioning is when you are interested in being able to drop whole partitions cheaply. regards, tom lane
