Topology documentation uses unexplained concepts
next_left_edge is mentioned a the docs for
Polygonize in the topology documentation. For instance in https://postgis.net/docs/TopologyPolygonize.html it says "Note: This function does not use nor set the next_left_edge and next_right_edge fields of the edge table."
However there is no documentation of what 'next_left_edge' means and what it does. The user is left without any way of figuring out what the consequences of that note are.