On Jan 6, 2008 11:27 AM, <
tomas@tuxteam.de> wrote:
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On Sun, Jan 06, 2008 at 01:12:32AM +0530, Gokulakannan Somasundaram wrote:
> On Jan 5, 2008 6:15 PM, <
tomas@tuxteam.de> wrote:
>
> >
> > One thought I had back then, with partitioned tables was "gee -- B-tree
> > index is already doing a partition; why do a manual partition on top of
> > that?".
> Can you please explain more on what you are trying to say here?
If you have , say, a table of orders (to use the example upthread) and a
B-tree index on order date, this index partitions your set (at
recursively finer levels).
But the current index scans - Index Scan and Bitmap Index Scan, doesn't provide the exact benefit of partitioning, even if all the columns are covered by the index. It does a lot more disk reads than the partitioning scheme. I think you are looking for something like Block indexes in Multi-dimensional Clusters in DB2. Heikki did something like that in a more subtle way.
Postgresql Clusters, as you may know doesn't maintain the order with inserts. We might go for Index Organized Tables/Clustered indexes. But then, B-tree would give lot of performance problems, if the Index Tuple size increases beyond a certain point.
Thanks,
Gokul.