Number of grid levels

You can have up to three grid levels.

For each grid level in a spatial grid index, a separate index search is performed during a spatial query. Therefore, if you have more grid levels, your query is less efficient.

If the values in the spatial column are about the same relative size, use a single grid level. However, a typical spatial column does not contain geometries of the same relative size, but geometries in a spatial column can be grouped according to size. You should correspond your grid levels with these geometry groupings.

For example, suppose you have a table of county land parcels with a spatial column that contains groupings of small urban parcels surrounded by larger rural parcels. Because the sizes of the parcels can be grouped into two groups (small urban ones and larger rural ones), you would specify two grid levels for the spatial grid index.