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ST_EstimatedExtent

ST_EstimatedExtent
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Name

ST_EstimatedExtent — Return the 'estimated' extent of the given spatial table. The estimated is taken from the geometry column's statistics. The current schema will be used if not specified.

Synopsis

box2d ST_EstimatedExtent ( text schema_name , text table_name , text geocolumn_name , boolean parent_ony ) ;

box2d ST_EstimatedExtent ( text schema_name , text table_name , text geocolumn_name ) ;

box2d ST_EstimatedExtent ( text table_name , text geocolumn_name ) ;

Description

Return the 'estimated' extent of the given spatial table. The estimated is taken from the geometry column's statistics. The current schema will be used if not specified. The default behavior is to also use statistics collected from children tables (tables with INHERITS) if available. If 'parent_ony' is set to TRUE, only statistics for the given table are used and children tables are ignored.

For PostgreSQL>=8.0.0 statistics are gathered by VACUUM ANALYZE and resulting extent will be about 95% of the real one.

[Note]

In absence of statistics (empty table or no ANALYZE called) this function returns NULL. Prior to version 1.5.4 an exception was thrown instead.

For PostgreSQL<8.0.0 statistics are gathered by update_geometry_stats() and resulting extent will be exact.

Availability: 1.0.0

Changed: 2.1.0. Up to 2.0.x this was called ST_Estimated_Extent.

This method supports Circular Strings and Curves

Examples 

SELECT ST_EstimatedExtent('ny', 'edges', 'the_geom');
--result--
BOX(-8877653 4912316,-8010225.5 5589284)

SELECT ST_EstimatedExtent('feature_poly', 'the_geom');
--result--
BOX(-124.659652709961 24.6830825805664,-67.7798080444336 49.0012092590332)

See Also

ST_Extent

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