Let's say there is a table 'polygon_a' and a table 'polygon_b'. Each table contains three polygon features. The polygon features are spatially equal.
CREATE TABLE polygon_a ( gid serial NOT NULL, geom geometry(polygon, your_SRID), CONSTRAINT polygon_a_pkey PRIMARY KEY (gid) ); CREATE TABLE polygon_b ( gid serial NOT NULL, geom geometry(polygon, your_SRID), CONSTRAINT polygon_b_pkey PRIMARY KEY (gid) );
Now I've created a view 'equals_false' to select all features from table 'polygon_a' where ST_Equals(polygon_a.geom, polygon_b.geom) is false. After using the QGIS 'Split features' tool to split a feature from table 'polygon_a' the view 'equals_false' returns two results.
CREATE VIEW equals_false AS SELECT polygon_a.gid, polygon_a.geom FROM polygon_a LEFT JOIN polygon_b ON ST_Equals(polygon_a.geom, polygon_b.geom) WHERE polygon_b.gid IS NULL;
But after using the 'Merge selected features' tool to merge the splitted features 'equals false' still returns a result. What's the reason of this behaviour?