SQL: Get the angles of segment breaks of a line table

lines.sql

with 
 -- dump the geometries
dumps as (
  select cartodb_id, 
         st_dumppoints(the_geom) as dp
    from ne_50m_rivers_lake_centerlines 
), 
-- get the points
points as ( 
     select cartodb_id,
            (dumps.dp).geom point ,
            (dumps.dp).path
       from dumps
   order by cartodb_id, (dumps.dp).path
), 
-- get the azimuths of a point against the previous and the next point
-- you may also want to get the distance between them
azimuths as ( 
  select
    cartodb_id, 
    path,  
    st_azimuth(
      lag(point) over (partition by cartodb_id order by path),
      point
    ) az_lag,  
    st_azimuth(
      point,
      lead(point) over (partition by cartodb_id order by path)
    ) az_lead
  from points
)
-- difference the azimuths, here you can start filtering by a threshold in radians or whatever
select cartodb_id, 
       path,
       case when az_lead is not null and az_lag is not null 
            then az_lead - az_lag 
            else null 
       end as az_diff
  from azimuths