Re: varying pagesize in postgresql

Thanks. Here is what exactly I am doing:

I am working on distributes spatial databases. I am trying to speed up join:

1. I am creating an external r*-tree index on the largest table
2. Then distributing the leaves of the r* tree on different nodes of a cluster(Each node has its own instance of the database) according to some hash function. Each node will ahve a few tuples of the first table and the tuples of the second table which overlap with the corresponding leaves.

3. Then I run Partition Based Spatial Merge Join algorithm on each node, which gives u the candidates for the join.

4. Then I use the distance function of postgis to find the actual join pairs, I run this query on each node and then concatenate the results of all nodes to get the join pairs.

IN the last step, when I am checking with the actual geometry, will there be any performance gain by increasing the pagesize??

My query for the last step would be:

select t1.gid, t2.gid from table1 as t1, table2 as t2 where distance(t1.the_geom, t2,the_geom)=0;

Any other help or ideas for speeding up the process, related to postgresql?

Thanks again,
gayatri.

Alvaro Herrera <alvherre(at)surnet(dot)cl> wrote:
[reformatted for sanity]

> On Mon, Jun 20, 2005 at 11:09:36PM -0700, gayatri ganpaa wrote:

> > How do I change the page size in postgresql? I have the postgresql-7.4.3 version.
> > I am trying to create an r*-tree index on a spatial table with
> > around 100,000 rows. I just want to check if increasing the page
> > size would make the join of two tables faster. Are there any other
> > options I could use to make this faster? Would increasing the page
> > size help?

On Tue, Jun 21, 2005 at 11:58:44AM -0500, Jim C. Nasby wrote:
> pg_dumpall
> Change something in one of the header files (which is docummented
> somewhere...)

BLCKSZ, in src/include/pg_config_manual.h. I doubt it would make the
index faster anyway ... I think you could post the query, schema, and
EXPLAIN ANALYZE to pgsql-performance so that people can give you further
advice. Going forward, rtree is somewhat obsolete -- maybe try setting
up a GiST index instead (not sure if it would be faster than rtree.)

--
Alvaro Herrera ()
"God is real, unless declared as int"

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