Postgis Raster merge geometry

Question

I have a raster table and a geometry table in postgis. My goal is to create a single raster merging elements from both:-

WITH geom_raster AS (

    SELECT wkb_geometry, ST_AsRaster(wkb_geometry, 200,200,ARRAY['8BUI', '8BUI', '8BUI'], ARRAY[118,154,118], ARRAY[0,0,0]) as rast FROM geometry_table
),
raster AS (

    SELECT ST_Union(rast) from raster_table,geom_raster where wkb_geomtry && rast
)
   SELECT ............

What is the last step to merge the two into a single raster so I see the geometry on top of the raster? I tried ST_Union but get an error about alignment which I suspect means the grids or SRIDS or something else are not in unison?

Answer 1

Answer was staring me in the face after a more detailed read of documentation:-

SELECT ST_AsRaster(ST_Buffer(wkb_geometry, 50), 
                  rast,
                  ARRAY['8BUI'], 
                  ARRAY[118]
                  )         
          as rast FROM  raster,geometry_table