DropGeometryColumn

DropGeometryColumn is a PostGIS utility function used to remove a geometry column from a table and clean up the associated metadata in the geometry_columns catalog. It was commonly used in older PostGIS installations to ensure that both the column and its metadata were properly deleted in one operation.

Usage and signature

The function is invoked within SQL as a simple call that specifies the target table and the geometry column to be removed. Typical forms include selecting from the fully qualified table name and column name, such as SELECT DropGeometryColumn('schema.table', 'geom'); in practice, the exact argument form may vary slightly by PostGIS version. The function returns void and performs the removal as a single atomic operation.

Behavior and effects

DropGeometryColumn removes the specified geometry column from the table and also deletes the corresponding entry from the geometry_columns metadata. It may also handle related constraints and dependencies as part of the cleanup process. The operation is destructive and not easily reversible, so it requires appropriate privileges and precautionary backups.

Prerequisites and cautions

Users must have sufficient permissions on the table to drop the column. It is important to verify that no dependent views, functions, or constraints rely on the geometry column before execution. Because the function alters metadata as well as the schema, it should be used only when a geometry column is truly no longer needed.

Modern context

In more recent PostGIS workflows, the standard SQL approach to removing a geometry column—ALTER TABLE table_name DROP COLUMN column_name—may be preferred, with PostGIS metadata updates occurring automatically in many setups. DropGeometryColumn remains available for compatibility with older scripts and workflows.

See also

PostGIS, geometry_columns, spatial_ref_sys.