Tom Lane <[EMAIL PROTECTED]> writes: > Global indexes would seriously reduce the performance of both vacuum and > cluster for a single partition, and if you want seq scans you don't need > an index for that at all. So the above doesn't strike me as a strong > argument for global indexes ...
I think he means some sort of plan for queries like select * from invoices where customer_id = 1 where customer 1 only did business with us for two years. One could imagine some kind of very coarse grained bitmap index that just knows which partitions customer_id=1 appears in, and then does a sequential scan of those partitions. But I think you can do nearly as well without using global indexes of any type. Assuming you had local indexes on customer_id for each partition and separate histograms for each partition the planner could conclude that it needs sequential scans for some partitions and a quick index lookup expecting 0 records for other partitions. Not as good as pruning partitions entirely but if you're doing a sequential scan the performance hit of a few index lookups isn't a problem. -- greg ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
