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Spatial Indexes Dialog Box (Visual Database Tools)

Use the Spatial Indexes dialog box to create indexes for columns of the geometry or geography data type (spatial columns), which cannot be indexed using the Index/Keys dialog box. Each spatial column can have more than one spatial index, but they must be created one at a time.

For information about restrictions on spatial index creation, see Spatial Indexes Overview.

Selected Spatial Index

Lists existing spatial indexes. Select an index to show its properties. If the list is empty, no spatial indexes have been defined for the table.

Add

Creates a new spatial index.

Delete

Deletes the spatial index selected in the Selected Spatial Index list.

Cells Per Object

Indicates the number of tessellation cells-per-object that can be used for a single spatial object in the index. This number can be any integer between 1 and 8192, inclusive. The default is 16.

If an object covers more cells than specified by n, the indexing uses as many cells as necessary to provide a complete top-level tessellation. In such cases, an object might receive more than the specified number of cells. In this case, the maximum number is the number of cells generated by the top-level grid, which depends on the Level 1 density.

Columns

Indicates the column name and sort order.

IsSpatialIndex

Indicates that a spatial index is selected.

Level 1

Indicates the density of the first-level (top) grid.

Level 2

Indicates the density of the second-level grid.

Level 3

Indicates the density of the third-level grid.

Level 4

Indicates the density of the fourth-level grid.

Tessellation Scheme

Indicates the tessellation scheme:

Geometry column options:

  • Geometry grid for a geometry column

  • Geography grid for a geography column

Type

Indicates that a spatial index is selected.

X-max

Specifies the x-coordinate of the upper-right corner of the bounding box. This property is dimmed if the Tessellation Scheme is Geography grid.

X-min

Specifies the x-coordinate of the lower-left corner of the bounding box. This property is dimmed if the Tessellation Scheme is Geography grid.

Y-max

Specifies the y-coordinate of upper-right corner of the bounding box. This property is dimmed if the Tessellation Scheme is Geography grid.

Y-min

Specifies the y-coordinate of the lower-left corner of the bounding box. This property is dimmed if the Tessellation Scheme is Geography grid.

Identity

When expanded, shows the Name and Description property fields.

(Name)

Shows the name of the spatial index. When a new index is created, it is given a default name based on the table in the active window in Table Designer. You can change the name at any time.

Description

Describes the index. To write a more detailed description, click Description and then click the ellipsis button () that appears to the right of the property field. This provides a larger area in which to write text.

Table Designer Category

When expanded, shows information about the properties of this spatial index.

Fill Specification

When expanded, shows information for Fill Factor and Pad Index.

Fill Factor

Specify what percentage of the index page the system can fill. When a page is full, if new data is added, the system must split the page, which impairs performance.

  • A value of 100 means the pages will be full; this requires the least amount of storage space but is the least efficient. This setting should be used only when there will be no changes to the data, for example, on a read-only table.

  • A lower value leaves more empty space on the data pages, which reduces the need to split data pages as indexes grow. However, it requires more storage space. This setting is more appropriate when there will be changes to the data in the table.

Pad Index

Provides pages in this index the same percentage of empty space (padding) that is specified in Fill Factor.

Page Locks Allowed

Specifies whether page-level locking is allowed on this index. Allowing or disallowing page-level locking affects database performance.

Re-compute Statistics

Specifies whether to compute new statistics when the index is created. Recomputing statistics slows the building of indexes but usually improves query performance.

Row Locks Allowed

Specifies whether row-level locking is allowed on this index. Allowing or disallowing row-level locking affects database performance.

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