On 03.06.2011 14:02, Alexander Korotkov wrote:
> Hackers,
>
> WIP patch of fast GiST index build is attached. Code is dirty and comments
> are lacking, but it works. Now it is ready for first benchmarks, which
> should prove efficiency of selected technique. It's time to compare fast
> GiST index build with repeat insert build on large enough datasets (datasets
> which don't fit to cache). There are following aims of testing:
> 1) Measure acceleration of index build.
> 2) Measure change in index quality.
> I'm going to do first testing using synthetic datasets. Everybody who have
> interesting real-life datasets for testing are welcome.
I did some quick performance testing of this. I installed postgis 1.5,
and loaded an extract of the OpenStreetMap data covering Finland. The
biggest gist index in that data set is the idx_nodes_geom index on nodes
table. I have maintenance_work_mem and shared_buffers both set to 512
MB, and this laptop has 4GB of RAM.
Without the patch, reindexing the index takes about 170 seconds and the
index size is 321 MB. And with the patch, it takes about 150 seconds,
and the resulting index size is 319 MB.
The nodes table is 618MB in size, so it fits in RAM. I presume the gain
would be bigger if it doesn't, as the random I/O to update the index
starts to hurt more. But this shows that even when it does, this patch
helps a little bit, and the resulting index size is comparable.
-- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com