Oracle8i Spatial User's Guide and Reference
Release 8.1.5

A67295-01

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6
Tuning Functions and Procedures for Object-Relational Model

This chapter contains descriptions of the tuning functions and procedures shown in Table 6-1.

Table 6-1 Tuning Functions and Procedures
Function/Procedure  Description 

SDO_TUNE.AVERAGE_MBR  

Calculates the average minimum bounding rectangle for geometries in a layer.  

SDO_TUNE.ESTIMATE_INDEX_PERFORMANCE  

Estimates the spatial index selectivity.  

SDO_TUNE.ESTIMATE_TILING_LEVEL  

Determines an appropriate tiling level for creating fixed-size index tiles.  

SDO_TUNE.ESTIMATE_TILING_TIME  

Estimates the tiling time for a layer, in seconds.  

SDO_TUNE.EXTENT_OF  

Determines the minimum bounding rectangle of the data in a layer.  

SDO_TUNE.HISTOGRAM_ANALYSIS  

Calculates statistical histograms for a spatial layer.  

SDO_TUNE.MIX_INFO  

Calculates geometry type information for a spatial layer, such as the percentage of each geometry type.  


SDO_TUNE.AVERAGE_MBR

Purpose

This function calculates the average minimum bounding rectangle (MBR) for all geometries in a column of type SDO_GEOMETRY.

Syntax

SDO_TUNE.AVERAGE_MBR (table_name, column_name, width, height)

Keywords and Parameters

table_name  

Specifies the name of the geometry table to examine.
Data type is VARCHAR2.  

column_name  

Specifies the name of the geometry object column to examine.
Data type is VARCHAR2.  

width  

Returns the width of the average MBR.
Data type is OUT NUMBER.  

height  

Returns the height of the average MBR.
Data type is OUT NUMBER.  

Returns

The function returns the width and height of the average MBR for all geometries in a geometry table.

Data types for height and width are NUMBER.

Usage Notes

This function calculates the average MBR by keeping track of the maximum and
minimum X and Y values for all geometries in a geometry table.


SDO_TUNE.ESTIMATE_INDEX_PERFORMANCE

Purpose

This function estimates the spatial index performance such as query selectivity and window query time for a column of type SDO_GEOMETRY.

Syntax

SDO_TUNE.ESTIMATE_INDEX_PERFORMANCE (table_name, column_name, sample_ratio,
tiling_level, num_tiles, window_object, tiling_time, filter_time, query_time
)

Keywords and Parameters

table_name  

Specifies the name of the geometry table to examine.
Data type is VARCHAR2.  

column_name  

Specifies the name of the geometry object column to examine.
Data type is VARCHAR2.  

sample_ratio  

Specifies the size ratio between the original layer and the sample layer to be generated.
Data type is INTEGER.
Default is 20.  

tiling_level  

Specifies the spatial index level at which the layer is to be tessellated.
Data type is INTEGER.  

num_tiles  

Specifies the number of tiles for variable or hybrid tessellation.
Data type is INTEGER.  

window_object  

Specifies the name of the spatial layer in which the query window is stored.
Data type is VARCHAR2.  

tiling_time  

Returns the estimated tiling time in seconds.
Data type is OUT NUMBER.  

filter_time  

Returns the estimated spatial index filter time in seconds.
Data type is OUT NUMBER.  

query_time  

Returns the estimated query window time in seconds.
Data type is OUT NUMBER.  

Returns

The function returns a number between 0.0 and 1.0 representing estimated spatial index selectivity. Data type is NUMBER.

The function also returns the estimated tiling time, filter time, and query time. Data type for these variables is NUMBER.

Usage Notes


SDO_TUNE.ESTIMATE_TILING_LEVEL

Purpose

This function estimates the appropriate sdo_level to use when indexing with hybrid or fixed-size tiles.

Syntax

MDSYS.SDO_TUNE.ESTIMATE_TILING_LEVEL (table_name, column_name, maxtiles,
type_of_estimate)

Keywords and Parameters

table_name  

Specifies the name of the geometry table.
Data type is VARCHAR2.  

column_name  

Specifies the name of the geometry column to examine.
Data type is VARCHAR2.  

maxtiles  

Specifies the maximum number of tiles that can be used to index the rectangle defined by the type_of_estimate parameter.
Data type is INTEGER.  

type_of_estimate  

Indicates by keyword one of three different models. Specify the type of estimate with one of the following keywords:LAYER_EXTENT -- Use the rectangle defined by your coordinate system. ALL_GID_EXTENT -- Use the minimum bounding rectangle that encompasses all the geometric objects in the column. This estimate is recommended for most applications with a maxtiles of 10,000.AVG_GID_EXTENT -- Use a rectangle representing the average size of the individual geometric objects within the column. This option performs the most analysis of the three types.

Data type is VARCHAR2.  

Returns

The function returns an integer representing the level to use when creating a spatial index for the specified layer. The function returns NULL if the data is inconsistent.

Usage Notes

None.

Related Topics


SDO_TUNE.ESTIMATE_TILING_TIME

Purpose

This function provides the estimated time to tessellate a column of type
SDO_GEOMETRY.

Syntax

SDO_TUNE.ESTIMATE_TILING_TIME (table_name, column_name, sample_ratio, tiling_level,
num_tiles
)

Keywords and Parameters

table_name  

Specifies the name of the geometry table to examine.
Data type is VARCHAR2.  

column_name  

Specifies the name of the geometry object column to examine.
Data type is VARCHAR2.  

sample_ratio  

Specifies the size ratio between the original layer and the sample layer to be generated.
Data type is INTEGER.
Default is 20.  

tiling_level  

Specifies the spatial index level at which the layer is to be tessellated.
Data type is INTEGER.  

num_tiles  

Specifies the number of tiles for variable or hybrid tessellation.
Data type is INTEGER.  

Returns

This function returns the estimated tiling time in seconds. A return of 0 indicates an error.

Data type is NUMBER.

Usage Notes

None.


SDO_TUNE.EXTENT_OF

Purpose

This function determines the extent of all geometries in a column of type
SDO_GEOMETRY.

Syntax

SDO_TUNE.EXTENT_OF (table_name, column_name)

Keywords and Parameters

table_name  

Specifies the name of the geometry table.
Data type is VARCHAR2.  

column_name  

Specifies the name of the geometry column to examine.
Data type is VARCHAR2.  

Returns

This function returns a geometry object representing the minimum bounding rectangle for all geometric data in a column. The function returns NULL if the data is inconsistent.

Usage Notes

None.

Related Topics

SDO_TUNE.ESTIMATE_TILING_LEVEL() function


SDO_TUNE.HISTOGRAM_ANALYSIS

Purpose

This procedure generates statistical histograms based on columns of type
SDO_GEOMETRY.

Syntax

SDO_TUNE.HISTOGRAM_ANALYSIS (table_name, column_name, result_table, type_of_histogram,
max_value, intervals
)

Keywords and Parameters

table_name  

Specifies the name of the geometry table to examine.
Data type is VARCHAR2.  

column_name  

Specifies the name of the geometry column to examine.
Data type is VARCHAR2.  

result_table  

Specifies the name of the result table where the histogram will be stored.
Data type is VARCHAR2.  

type_of_histogram  

Specifies one of three types of histograms:TILES_VS_LEVEL (default)GEOMS_VS_AREAGEOMS_VS_VERTICES

Data type is VARCHAR2.  

max_value  

Specifies the upper limit of the histogram.
Data type is NUMBER.  

intervals  

Specifies the number of intervals between 0 and max_value.
Data type is INTEGER.  

Returns

The procedure populates the result table with statistical histograms for a geometry table.

Usage Notes


SDO_TUNE.MIX_INFO

Purpose

This procedure provides the number of geometries of each type stored in a column of type SDO_GEOMETRY.

Syntax

SDO_TUNE.MIX_INFO (table_name, column_name)

Keywords and Parameters

table_name  

Specifies the name of the geometry table to examine.
Data type is VARCHAR2.  

column_name  

Specifies the name of the geometry column to examine.
Data type is VARCHAR2.  

Returns

The procedure calculates geometry type information for the table. It calculates the number of geometries of different types, as well as the percentages of points, line strings, polygons, and complex geometries.

Usage Notes

None.




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