title: Calculate length of a shared edge of two polygones in PostGIS
body: <p>I have a database of several polygones. Each polygon has a lot of nodes which define it. Additionally each polygone has at least one neighbour. For a calculation I need to determine the length of the shared edge of two neighboured polygones. In the example picture such a case is shown. The two polygones share the red edges. How can I calculate the length of the red edge with the help of PostGIS? I didn't find a function for that.</p>
  
  <p><a href="https://i.stack.imgur.com/xePr9.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/xePr9.png" alt="Example of two polygones that share two edges"></a></p>