How can I make buffer with ST_Buffer in PostGIS

Question

I am trying to make a buffer(0) as a fix-geometry process in PostGIS 2.2.2. It like this:

SELECT ST_Buffer(ST_GeomFromText('POINT(100 90)'),0,4);

I am using sources from this man-page. It creates an output that goes like this:

  ----------------------
  010300000000000000000
  (1 row)

But I am not sure if I am actually just simulating the creation of a buffer in PostGIS or I am actually making a buffer on database#scheme.table

What I would like to is to make an ST_Buffer of all the geometries (polygon) in the table. Seems like getting something wrong. The syntax is foreign to me though.

I have experienced that it isn't like: ST_Buffer(scheme.table, 0) but how am I to understand these examples?

Answer 1

What you want is:

SELECT ST_Buffer(geometry_column, 0) FROM scheme.table

Where geometry_column is the column within your table (scheme.table) that contains your geometry.

You current result of:

  ----------------------
  010300000000000000000
  (1 row)

Looks correct, that is the well known binary version of the geometry, or how PostgreSQL sees it. For human readable try:

SELECT ST_AsText(ST_Buffer(ST_GeomFromText('POINT(100 90)'),0,4));

Result:

POLYGON EMPTY

Obviously a 0 unit buffer of a point will result in an empty polygon.

While that is one way to fix geometries. A better solution would be ST_MakeValid.