Hello I have the following problem:
I created a grid in QGIS. For some unknown reason QGIS doesn't tesselate the plane correctly. Sometimes there are polygons with different "id" that represents the same portion of the area. I loaded the Shapefile into postgis (without noticing this) and began to have troubles in queries. When I look for the problem I saw that sometimes 2 or even 4 polygons represent exactly the same region. How could I delete those repeating polygons?