Thanks for you previous help and quick responses. I'm only getting to look at
your suggestions now, however I noticed in PostGIS 2.0 the ST_ConcaveHull()
which is closer to our functionality needs so have started to try and work with
this instead of the convexhull option. Maybe another to-do re aggregate
operations of both these functions. Anyway I started my first test
implementation from your suggestions in the following form: WITH ctsubgroup AS
( SELECT ST_ConcaveHull(ST_Force_2D(ST_Union(local_geom)), 0.9) As geom
FROM lidar_099 GROUP BY ST_SnapToGrid(local_geom, 10,10))SELECT
ST_AsEWKT(ST_ConcaveHull(ST_Union(geom), 0.9))FROM ctsubgroup; The table in
question has 62 million popints and is a small one. The Query is still running
after 6 hours but quite quickly it reported the following:
**************PGADMIN MESSAGE - START**************NOTICE:
geometry_gist_joinsel called with incorrect join type
CONTEXT: SQL statement "SELECT ST_Union(ARRAY(SELECT geom
FROM (
-- fuse near neighbors together
SELECT DISTINCT ON (i) i,
ST_Distance(var_atempgeoms[i],var_atempgeoms[j]),
ST_Buffer(ST_MakeLine(var_atempgeoms[i], var_atempgeoms[j]) , var_buf*5,
'quad_segs=3') As geom
FROM generate_series(1,array_upper(var_atempgeoms, 1)) As i
INNER JOIN generate_series(1,array_upper(var_atempgeoms, 1)) As j
ON (
NOT ST_Intersects(var_atempgeoms[i],var_atempgeoms[j])
AND ST_DWithin(var_atempgeoms[i],var_atempgeoms[j], var_buf*10)
)
UNION ALL
-- catch the ones with no near neighbors
SELECT i, 0, ST_Buffer(var_atempgeoms[i] , var_buf*10, 'quad_segs=3')
As geom
FROM generate_series(1,array_upper(var_atempgeoms, 1)) As i
LEFT JOIN
generate_series(ceiling(array_upper(var_atempgeoms,1)/2)::integer,array_upper(var_atempgeoms,
1)) As j
ON (
NOT ST_Intersects(var_atempgeoms[i],var_atempgeoms[j])
AND ST_DWithin(var_atempgeoms[i],var_atempgeoms[j], var_buf*10)
)
WHERE j IS NULL
ORDER BY 1, 2
) As foo ) )"
PL/pgSQL function "st_concavehull" line 39 at assignment
NOTICE: geometry_gist_joinsel called with incorrect join type
CONTEXT: SQL statement "SELECT ST_Union(ARRAY(SELECT geom
FROM (
-- fuse near neighbors together
SELECT DISTINCT ON (i) i,
ST_Distance(var_atempgeoms[i],var_atempgeoms[j]),
ST_Buffer(ST_MakeLine(var_atempgeoms[i], var_atempgeoms[j]) , var_buf*5,
'quad_segs=3') As geom
FROM generate_series(1,array_upper(var_atempgeoms, 1)) As i
INNER JOIN generate_series(1,array_upper(var_atempgeoms, 1)) As j
ON (
NOT ST_Intersects(var_atempgeoms[i],var_atempgeoms[j])
AND ST_DWithin(var_atempgeoms[i],var_atempgeoms[j], var_buf*10)
)
UNION ALL
-- catch the ones with no near neighbors
SELECT i, 0, ST_Buffer(var_atempgeoms[i] , var_buf*10, 'quad_segs=3')
As geom
FROM generate_series(1,array_upper(var_atempgeoms, 1)) As i
LEFT JOIN
generate_series(ceiling(array_upper(var_atempgeoms,1)/2)::integer,array_upper(var_atempgeoms,
1)) As j
ON (
NOT ST_Intersects(var_atempgeoms[i],var_atempgeoms[j])
AND ST_DWithin(var_atempgeoms[i],var_atempgeoms[j], var_buf*10)
)
WHERE j IS NULL
ORDER BY 1, 2
) As foo ) )"
PL/pgSQL function "st_concavehull" line 39 at assignment
NOTICE: geometry_gist_joinsel called with incorrect join type
CONTEXT: SQL statement "SELECT ST_Union(ARRAY(SELECT geom
FROM (
-- fuse near neighbors together
SELECT DISTINCT ON (i) i,
ST_Distance(var_atempgeoms[i],var_atempgeoms[j]),
ST_Buffer(ST_MakeLine(var_atempgeoms[i], var_atempgeoms[j]) , var_buf*5,
'quad_segs=3') As geom
FROM generate_series(1,array_upper(var_atempgeoms, 1)) As i
INNER JOIN generate_series(1,array_upper(var_atempgeoms, 1)) As j
ON (
NOT ST_Intersects(var_atempgeoms[i],var_atempgeoms[j])
AND ST_DWithin(var_atempgeoms[i],var_atempgeoms[j], var_buf*10)
)
UNION ALL
-- catch the ones with no near neighbors
SELECT i, 0, ST_Buffer(var_atempgeoms[i] , var_buf*10, 'quad_segs=3')
As geom
FROM generate_series(1,array_upper(var_atempgeoms, 1)) As i
LEFT JOIN
generate_series(ceiling(array_upper(var_atempgeoms,1)/2)::integer,array_upper(var_atempgeoms,
1)) As j
ON (
NOT ST_Intersects(var_atempgeoms[i],var_atempgeoms[j])
AND ST_DWithin(var_atempgeoms[i],var_atempgeoms[j], var_buf*10)
)
WHERE j IS NULL
ORDER BY 1, 2
) As foo ) )"
PL/pgSQL function "st_concavehull" line 39 at assignment**************PGADMIN
MESSAGE - END************** Is this a significant issue as the Query still
seems to be running. Cheers, Paul _______________________________________________
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