GeoJsonWrite

Signatures

GeoJsonWrite(VARCHAR path, VARCHAR tableName);
GeoJsonWrite(VARCHAR path, VARCHAR tableName, BOOLEAN deleteTable);

Description

Writes the contents of table tableName to a GeoJSON file located at path.

tableName can be either:

the name of an existing table,
the result of a query (SELECT instruction which has to be written between simple quote and parenthesis '( )'). Warning: when using text value in the WHERE condition, you have to double the simple quote (different from double quote “”): ... WHERE TextColumn = ''myText''.

The .geojson file may be zipped in a .gz file (in this case, the GeoJsonWrite driver will zip on the fly the .geojson file).

If the deleteTable parameter is true and path file already exists, then path file will be removed / replaced by the new one. Else (no deleteTable parameter or deleteTable equal to false), an error indicating that the path file already exists will be throwned.

Examples

In the following example, we are working with a table named TEST and defined as follow.

CREATE TABLE TEST(ID INT PRIMARY KEY, THE_GEOM GEOMETRY(POINT));
INSERT INTO TEST VALUES (1, 'POINT(0 1)');
INSERT INTO TEST VALUES (2, 'POINT(2 4)');

1. Case with `path` and `tableName`

-- Write a spatial table to a GeoJSON file:
CALL GeoJsonWrite('/home/user/test.geojson', 'TEST');

-- Read it back:
CALL GeoJsonRead('/home/user/test.geojson', 'TEST2');
SELECT * FROM TEST2;

Answer:

ID	THE_GEOM
1	POINT(0 1)
2	POINT(2 4)

If you want to compress your resulting .geojson file into a .gz file, just execute

CALL GeoJsonWrite('/home/user/test.geojson.gz', 'TEST');

As a result, you will obtain a test.geojson.gz file in which there is the test.geojson resulting file.

2. Case where `tableName` is the result of a selection

CALL GeoJsonWrite('/home/user/test.geojson', 
                  '(SELECT * FROM TEST WHERE ID<2 )');
-- Read it back:
CALL GeoJsonRead('/home/user/test.geojson', 'TEST2');
SELECT * FROM TEST2;