Spatial Indexes

[JenniferDick]

I'm applying spatial indexes to a few layers that reside in a geodatabase. We are testing the concept of spatial indexing for the purposes of performance improvement.

A few of the layers we would like to put indexing on have for example, (on a point line) over 730,000 points. I've calculated the default spatial grid index using geoprocessing tools and have then used 'Add Spatial Index' tool to apply the grids calculated prior.

Now I'm trying to review the grid sizes and confirm that they were apply correctly using the layer properties. Unfortunately, they aren't listed under the index tab in the properties. Reading about this, it seems like the grid values should be listed here, and I should also have the ability to create, delete, recalculate. Though my only 2 options are 'Create' and 'Delete' and one of those are grayed out.

I'm hoping someone can provide some guidance in this area. I would like to confirm that the values Arc calculated are in fact there.

I've attached a screen shot of the later properties for your reference.

Please help,

Thank You

Jennifer

[VinceAngelo]

I didn't make a distinction for a reason -- Forcing index use when the constraint does not significantly reduce the result set is not likely to improve performance, especially if the table is fragmented with respect to the indexed column(s).  This is why optimizers collect statistics -- to get a sense of whether the index will help or hurt, and which index will help most.

- C

[JenniferDick]

Thanks for your thoughts Vince

[JenniferDick]

Another reason that it may be problematic to apply a spatial or attribute index is when the layer is consistently updated. The layers I speak up are often updated and what I've read is that each time you update a layer that is spatially index, you have to update the index.

[VinceAngelo]

No, once an index is built, additional inserts/updates/deletes are manifested as they should.  It's probably a good idea to periodically refresh the indexes, and you want to be careful on the number of unnecessary indexes with large, frequently updated tables, but it's certainly not necessary with each delta.

- V

[ThomasColson]

Witch Magic, Snake Oil Medicine, and Spatial Index Tuning