FT_Delete#

Summary#

FT_Delete makes the deletion of a spatial object indexed in a spatial index. It returns true if the deletion is successfully performed and false otherwise.

Signatures#

Bool FT_Delete(text index_name, text index_directory, integer pointer, Geometry geom);

Bool FT_Delete(text apath, integer pointer, Geometry geom);

Description#

FT_Delete makes the deletion of a spatial object indexed in a spatial index. It returns true if the deletion is successfully performed and false otherwise.

Note

FT_Delete does not automatically collect statistical data of the deletion. To do this collection, make use of its equivalent atomic operation or construct workloads with auxiliary operations.

FT_Delete has two versions and its parameters are:

index_name is the name of the index file.
index_directory is the directory path that stores the index file.
apath is the absolute path of the index file.
pointer is the primary key value of the spatial object to be deleted. That is, the unique identifier that provides direct access to the register storing the spatial object.
geom is the spatial object (i.e., a PostGIS object) to be deleted.

Caution

The connected user of the database must be permission to read and write in the directory storing the index file. Otherwise, an error is returned.

Warning

It is important to keep the correspondence between the spatial index and its underlying spatial dataset. Hence, make sure that every indexed spatial object also exists in its underlying spatial dataset. This kind of control is out of scope of FESTIval.

Examples#

--using the first version of FT_Delete to delete the rectangular shaped object of the FT_Insert example
SELECT FT_Delete('r-tree', '/opt/festival_indices/', 50, 
    ST_GeomFromText('POLYGON((-6349160.26886151 -751965.038197354,-6349160.26886151 -606557.85245731,-6211936.96741955 -606557.85245731,-6211936.96741955 -751965.038197354,-6349160.26886151 -751965.038197354))', 3857)
    );

--using the second version of FT_Delete to delete a spatial object from a spatial index. The spatial object is obtained from the underlying spatial dataset of the spatial index
SELECT FT_Delete('/opt/festival_indices/rstartree-brazil_points2017', 1000, 
    (SELECT way FROM brazil_points2017 WHERE id = 1000)
    );