Re: Spatial Index mysteries

In article <95b60q$2tk$1_at_nnrp1.deja.com>,   ribault_at_my-deja.com wrote:
> Hi,
>
> I have some difficulties understanding the spatial indexes behavior. I
> am using the Object-relational model in 8.1.6.
> First, I looked in the user guide the way to create a spatial index,
> and there is an explaination stating that if you don't put the
> SDO_LEVEL and SDO_NUMTILES parameter values, there will be an error.
> Since I have no clue about what values I should provide, I use the
> SDO_TUNE.ESTIMATE_TILING_LEVEL that gives me a value, and create the
> index from that. It works, until I try to rebuild the index using
 ALTER
> INDEX REBUILD. The error is displayed below:
> ERROR at line 1:
> ORA-29855: error occurred in the execution of ODCIINDEXCREATE routine
> ORA-13209: internal error while reading SDO_INDEX_METADATA table
> ORA-06512: at "MDSYS.SDO_INDEX_METHOD", line 83
> ORA-06512: at line 1
>
> Now, If I try to create the index without parameters, not only it
> works, but the index rebuild also work. And I don't really notice a
> difference in apparent performance.
>
> Am I missing something about the spatial index parameters ?
>
> --
> Pierre-Laurent Ribault
> Shizuoka, Japan
>
> Sent via Deja.com
> http://www.deja.com/
>

You need to be very aware of what version of the documentation you are looking at as compared to the version of Oracle you are running. The SDO_LEVEL and SDO_NUMTILES parameters only apply to Quad-Tree indexes. As of 8.1.6 Oracle included a beta copy of a new indexing scheme for spatial indexes: R-Tree indexes. Depending on the documentation you are looking at, it may or may not even mention anything about R-Tree. Also, the doc's may indicate that R-Tree is "to be released in a future version".

When you created your spatial index without the SDO_LEVEL and SDO_NUMTILES parameters, you implicitly created an R-Tree index instead of a Quad-Tree index. Note that in almost all cases R-Tree's will outperform Quad-Tree's. I'm pretty sure that Quad-Tree's will get desupported sometime in the near future.

Check out the info on R-Tree indexes on OTN at: http://technet.oracle.com/doc/oracle8i_816/inter.816/spatial_rtree/toc.h tm.

HTH. Matt.

Sent via Deja.com
http://www.deja.com/ Received on Thu Feb 01 2001 - 06:16:02 CST