Sorry, just caught up with the last couple of day’s email and I feel that this question has already been answered fairly comprehensively. Apologies.
Z From: Peter Marron [mailto:peter.mar...@trilliumsoftware.com] Sent: 04 July 2013 08:37 To: user@hive.apache.org Subject: RE: Partition performance Hi, Just to check that I understand this problem, my reading suggests that the overhead of many partitions is currently unavoidable. Specifically this means that any query on a table that has, let’s say, 10,000 partitions will be significantly slower (than on un-partitioned table with the “same” data) even if the query explicitly specifies a single partition. (I mean I _could_ actually do the experiments myself…) Regards, Z From: Owen O'Malley [mailto:omal...@apache.org] Sent: 02 July 2013 15:52 To: user@hive.apache.org<mailto:user@hive.apache.org> Subject: Re: Partition performance On Tue, Jul 2, 2013 at 2:34 AM, Peter Marron <peter.mar...@trilliumsoftware.com<mailto:peter.mar...@trilliumsoftware.com>> wrote: Hi Owen, I’m curious about this advice about partitioning. Is there some fundamental reason why Hive is slow when the number of partitions is 10,000 rather than 1,000? The precise numbers don't matter. I wanted to give people a ballpark range that they should be looking at. Most tables at 1000 partitions won't cause big slow downs, but the cost scales with the number of partitions. By the time you are at 10,000 the cost is noticeable. I have one customer who has a table with 1.2 million partitions. That causes a lot of slow downs. And the improvements that you mention are they going to be in version 12? Is there a JIRA raised so that I can track them? (It’s not currently a problem for me but I can see that I am going to need to be able to explain the situation.) I think this is the one they will use: https://issues.apache.org/jira/browse/HIVE-4051 -- Owen
