FT_ADelete#

Summary#

FT_ADelete is the atomic version of FT_Delete. It makes the deletion of a spatial object indexed in a spatial index, and collects and stores related statistical data. It returns the primary key value that corresponds to the identifier of the row inserted into the table Execution.

Signatures#

integer FT_ADelete(text index_name, text index_directory, integer pointer, Geometry geom, integer statistic_option=1, integer loc_stat_data=1, text file=NULL);

integer FT_ADelete(text apath, integer pointer, Geometry geom, integer statistic_option=1, integer loc_stat_data=1, text file=NULL);

Description#

FT_ADelete is the atomic version of FT_Delete. It makes the deletion of a spatial object indexed in a spatial index, and collects and stores related statistical data. It returns the primary key value that corresponds to the identifier of the row inserted into the table Execution.

Note

FT_ADelete is atomic because it executes three SQL functions as a unique operation.

FT_ADelete 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.
statistic_option refers to the type of statistical data to be collected and stored. If statistic_option is equal to 1, its default value, FESTIval collects standard statistical data to be inserted as a new tuple in the table Execution. If statistic_option is equal to 2 or 4, FESTIval collects statistical data related to the structure of the index to be inserted as a new tuple in the table IndexSnapshot. If statistic_option is equal to 3 or 4, FESTIval collects the nodes of the index to be inserted as new tuples in the table PrintIndex. Note that the value 4 indicates, therefore, that all types of statistical data is collected and stored.
loc_stat_data defines where the statistical data should be stored. If its value is equal to 1, its default value, the statistical data is stored directly in the FESTIval’s data schema. If its value is equal to 2, the statistical data is stored in a SQL file that can be latter loaded into the FESTIval’s data schema.
file is the absolute path of the SQL file that will store the statistical data, if loc_stat_data is equal to 2. This file will be created if it does not exist. This parameter is not used if loc_stat_data is equal to 1.

Note

We recommend that you see the FESTIval's data schema in order to understand the types of statistical data that can be managed.
If loc_stat_data is equal to 2, the returning value is invalid since the insertion is not made directly on the table Execution. A valid treatment is performed on the file storing the statistical data.

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.
If loc_stat_data is equal to 2, the connected user of the database must be permission to write in the directory storing this SQL 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_ADelete to delete a rectangular shaped object. It employs the default values of statistical data.
SELECT FT_ADelete('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_ADelete to delete a spatial object from a spatial index. It informs specific information for collecting statistical data
SELECT FT_ADelete('/opt/festival_indices/rstartree-brazil_points2017', 1000, 
    (SELECT way FROM brazil_points2017 WHERE id = 1000),
    2, 2, '/opt/statistical_data.sql'
    );