Creating Postgis Polygon using ST_ConcaveHull from Geometry Points

Question

I have a postgis 2.2 table with 20 columns of type geometry(Point,4326)

I'd like to generate a polygon which covers the outer boundary of the points - it seems like ST_ConcaveHull is a good option, but I can't see how to do it without first converting my points back to text (which seems to be missing the point).

Is st_concavehull the right option, and how do I go about constructing the query?

Answer 1

Some 'ugly but working' resolution on example :

Let's create a table:

create table test_concave (
  point1 geometry, 
  point2 geometry, 
  point3 geometry,
  point4 geometry,
  poly geometry);

Now insert some data into it:

insert into test_concave values (
  ST_GeomFromText('POINT(1 0)'),
  ST_GeomFromText('POINT(0 1)'),
  ST_GeomFromText('POINT(-1 0)'),
  ST_GeomFromText('POINT(0 -1)'),
  null)

Now We'll update column 'poly' with ST_ConcaveHull:

update test_concave set poly = 
  ST_ConcaveHull(
    ST_Collect(
      ST_Collect(
        ST_Collect(point1,point2)
      ,point3)
    ,point4)
  ,1);

The ugly part is that You need as many ST_Colleect functions as many you have geometry columns -1.

Answer as good as good was the question, but maybe it'll help.