Support is provided in CA ERwin Data Modeler for SQL Server 2008 spatial indexes. A spatial index is an index on a table based on spatial data in the table (using spatial columns). Spatial data uses the new data types, GEOMETRY and GEOGRAPHY, support of which is also included. Different tessellation schemes are used depending on the data type of the spatial column; a spatial column assigned the GEOMETRY data type uses the GEOMETRY_GRID tessellation scheme, while a spatial column assigned the GEOGRAPHIC data type uses the GEOGRAPHY_GRID tessellation scheme.
Use the SQL Server Table Spatial Index Editor to define general options, tessellation options, and boundary box options for your table spatial index.
The table spatial index options provide a way for you to define how the index behaves, such as using index padding, how to store temporary sort results used to build the index, whether distribution statistics are recomputed, allowing row or page locks, and so on.
Tessellation options let you specify the density of the grid at each level of a tessellation scheme and define the number of tessellation cells per object that you can use for a single spatial index object during the tessellation process. There are four levels for which you can specify density, and there are three density values you can select:
Specifies to use the lowest density for the grid. Low equals 16 cells, or a 4x4 grid.
Specifies to use the medium density for the grid at the given level. Medium equals 64 cells, or an 8x8 grid.
Specifies to use the highest possible density for the grid at the given level. High equals 256 cells, or a 16x16 grid.
Use the boundary box options to set the four coordinates of the bounding box when GEOMETRY_GRID is your tessellation scheme.
Note: For more information about spatial indexes, spatial data and its data types, and tessellation and density, see your SQL Server 2008 documentation.
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