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CREATE TABLE geoms (geom geometry);
-- Create 20x20 square polygons
WITH coords AS (SELECT * FROM generate_series(0, 19) AS x, generate_series(0, 19) AS y)
INSERT INTO geoms
SELECT ST_Square(1.0, x, y, ST_MakePoint(0, 0))
FROM coords;
WITH u AS (SELECT ST_Union(geom) AS g FROM geoms)
SELECT ST_Area(g), ST_XMin((g)), ST_YMin(g), ST_XMax(g), ST_YMax(g) from u;
-- NOTE: using gridSize > 0 requires GEOS-3.9 or higher
WITH u AS (SELECT ST_Union(geom, -1.0) AS g FROM geoms)
SELECT ST_Area(g), ST_XMin((g)), sT_YMin(g), ST_XMax(g), ST_YMax(g) from u;
TRUNCATE TABLE geoms;
-- Empty table
SELECT ST_Union(geom) IS NULL FROM geoms;
-- NULLs
INSERT INTO geoms (geom) VALUES (NULL), (NULL), (NULL), (NULL), (NULL);
SELECT ST_Union(geom) IS NULL FROM geoms;
-- Add empty point
INSERT INTO geoms SELECT ST_GeomFromText('POINT EMPTY') AS geom;
SELECT ST_AsText(ST_Union(geom)) FROM geoms;
-- Add empty polygon
INSERT INTO geoms SELECT ST_GeomFromText('POLYGON EMPTY') AS geom;
SELECT ST_AsText(ST_Union(geom)) FROM geoms;
-- Test in parallel mode
TRUNCATE TABLE geoms;
SET force_parallel_mode = on;
SET parallel_setup_cost = 0;
SET parallel_tuple_cost = 0;
SET min_parallel_table_scan_size = 0;
SET max_parallel_workers_per_gather = 4;
WITH coords AS (SELECT * FROM generate_series(0, 19) AS x, generate_series(0, 19) AS y)
INSERT INTO geoms
SELECT ST_Square(1.0, x, y, ST_MakePoint(0, 0))
FROM coords;
WITH u AS (SELECT ST_Union(geom) AS g FROM geoms)
SELECT ST_Area(g), ST_XMin((g)), ST_YMin(g), ST_XMax(g), ST_YMax(g) from u;
WITH u AS (SELECT ST_Union(geom, -1.0) AS g FROM geoms)
SELECT ST_Area(g), ST_XMin((g)), sT_YMin(g), ST_XMax(g), ST_YMax(g) from u;
TRUNCATE TABLE geoms;
SELECT ST_Union(geom) IS NULL FROM geoms;
INSERT INTO geoms (geom) VALUES (NULL), (NULL), (NULL), (NULL), (NULL);
SELECT ST_Union(geom) IS NULL FROM geoms;
INSERT INTO geoms SELECT ST_GeomFromText('POINT EMPTY') AS geom;
SELECT ST_AsText(ST_Union(geom)) FROM geoms;
INSERT INTO geoms SELECT ST_GeomFromText('POLYGON EMPTY') AS geom;
SELECT ST_AsText(ST_Union(geom)) FROM geoms;
DROP TABLE geoms;
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