CREATE TABLE s_test(geom geometry); 
		INSERT INTO s_test(geom) VALUES(ST_GeomFromText('MULTIPOINT(
(120 -224), (185 -219), (190 -234), (200 -246), (212 -256), (227 -261), 
(242 -264), (257 -265), (272 -264), (287 -263),(302 -258), (315 -250),
(323 -237), (321 -222), (308 -213), (293 -208), (278 -205), (263 -202),
(248 -199), (233 -196), (218 -193), (203 -190), (188 -185), (173 -180),
(160 -172), (148 -162), (138 -150), (133 -135), (132 -120), (136 -105), 
(146  -92), (158  -82), (171  -74), (186  -69), (201  -65), (216  -62),
(231  -60), (246  -60), (261  -60), (276  -60), (291  -61), (306  -64),
(321  -67), (336  -72), (349  -80), (362  -89), (372 -101), (379 -115),
(382 -130), (314 -134), (309 -119), (298 -108), (284 -102), (269 -100), 
(254  -99), (239 -100), (224 -102), (209 -107), (197 -117), (200 -132), 
(213 -140), (228 -145), (243 -148), (258 -151), (273 -154), (288 -156), 
(303 -159), (318 -163), (333 -167), (347 -173), (361 -179), (373 -189), 
(383 -201), (389 -215), (391 -230), (390 -245), (384 -259), (374 -271), 
(363 -282), (349 -289), (335 -295), (320 -299), (305 -302), (290 -304),
(275 -305), (259 -305), (243 -305), (228 -304), (213 -302), (198 -300), 
(183 -295), (169 -289), (155 -282), (143 -272), (133 -260), (126 -246), 
(136 -223), (152 -222), (168 -221), (365 -131), (348 -132), (331 -133), 
(251 -177), (183 -157), (342  -98), (247  -75), (274 -174), (360 -223),
(192  -85), (330 -273), (210 -283), (326  -97), (177 -103), (315 -188),
(175 -139), (366 -250), (321 -204), (344 -232), (331 -113), (162 -129), 
(272  -77), (292 -192), (144 -244), (196 -272), (212  -89), (166 -236), 
(238 -167), (289 -282), (333 -187), (341 -249), (164 -113), (238 -283),
(344 -265), (176 -248), (312 -273), (299  -85), (154 -261), (265 -287),
(359 -111), (160 -150), (212 -169), (351 -199), (160  -98), (228  -77),
(376 -224), (148 -120), (174 -272), (194 -100), (292 -173), (341 -212), 
(369 -209), (189 -258), (198 -159), (275 -190), (322  -82))') ) ;

SELECT ST_AsBinary(
geom
)
FROM  s_test ;
		

SELECT ST_AsBinary(
ST_ConcaveHull(ST_Collect(geom),0.99)
)
FROM s_test;

SELECT ST_AsBinary(
ST_ConcaveHull(geom,0.90)
)
FROM  s_test ;

SELECT ST_AsBinary(
ST_ConcaveHull(geom,0.90,true)
)
FROM  s_test;

SELECT ST_AsBinary(
 ST_ConvexHull(ST_Collect(geom))
        )
FROM s_test ;

SELECT ST_AsBinary(
ST_ConcaveHull(ST_Collect(geom),0.80)
 )
 FROM stumper;

SELECT ST_AsBinary(
 ST_ConvexHull(ST_Collect(geom))
 )
 FROM stumper; 

CREATE TABLE pointwave(gid serial primary key, geom geometry);
INSERT INTO pointwave(geom)
SELECT ST_Point(i*random(),j*random()) As the_geom 
FROM generate_series(1,100) As i 
	CROSS JOIN generate_series(-20,20) As j ;
SELECT geom FROM pointwave;
		

SELECT ST_AsBinary(
 ST_ConcaveHull(
    ST_Collect(geom),0.80
    )
   )
 FROM pointwave;

SELECT ST_AsBinary(
 ST_ConcaveHull(
    ST_Collect(geom),0.50
    )
   )
 FROM pointwave;

SELECT ST_AsBinary(ST_ConvexHull(ST_Collect(geom)))
 FROM stumper; 

SELECT ST_AsBinary(geom) 
FROM pointlocs 
WHERE geom IS NOT NULL;
		

SELECT ST_AsBinary( ST_ConcaveHull( ST_Collect(geom),0.99 ) )
FROM pointlocs
    WHERE geom IS NOT NULL;

SELECT ST_AsBinary( ST_ConcaveHull( ST_Collect(geom),0.90 ) )
FROM pointlocs
    WHERE geom IS NOT NULL;

SELECT ST_AsBinary( ST_ConcaveHull( ST_Collect(geom),0.90 ),true )
FROM pointlocs
    WHERE geom IS NOT NULL;

SELECT ST_AsBinary( ST_ConcaveHull( ST_Collect(geom),0.70 ) )
FROM pointlocs
    WHERE geom IS NOT NULL;

SELECT ST_AsBinary( ST_ConcaveHull( ST_Collect(geom),0.70,true ) )
FROM pointlocs
    WHERE geom IS NOT NULL;

SELECT ST_AsBinary( 
    ST_ConvexHull( ST_Collect(geom)
        )
      )
FROM pointlocs
WHERE geom IS NOT NULL;

SELECT ST_Union(geom) FROM neighborhoods;
		

SELECT ST_AsBinary(
    ST_ConcaveHull(ST_Union(geom),0.99)
			)
FROM neighborhoods;

SELECT ST_AsBinary(
    ST_ConcaveHull(ST_Union(geom),0.90)
			)
FROM neighborhoods;

SELECT ST_AsBinary(
    ST_ConcaveHull(ST_Union(geom),0.70)
			)
FROM neighborhoods;

SELECT ST_AsBinary(
    ST_ConcaveHull(ST_Union(geom),0.70)
			)
FROM neighborhoods;

SELECT ST_AsBinary(
 ST_ConvexHull(ST_Union(the_geom))
        )
FROM neighborhoods; 

SELECT ST_AsBinary(
geom
)
FROM  mbta_busroutes ;
		

Note: In some cases the 99% (such as this example) gives a better and much faster result than some of the lower compressions. This is because of GEOS topological errors we run into that force the alogrithm to fall back on the convexhull for certain regions. So as a general rule, try the 99% first. It is generally much much faster than lower percentages, for fairly huge patches of empty area, also returns an areal percentage much less than the convexhull, and is also less likely to run into topological issues

SELECT ST_AsBinary(
ST_ConcaveHull(ST_Collect(geom),0.99)
)
FROM  mbta_busroutes 
;

SELECT ST_AsBinary(
ST_ConcaveHull(ST_Collect(geom),0.90)
)
FROM  mbta_busroutes 
;

SELECT ST_AsBinary(
ST_ConcaveHull(ST_Collect(geom),0.70)
)
FROM  mbta_busroutes;

SELECT ST_AsBinary(
ST_ConcaveHull(ST_Collect(geom),0.70, true)
)
FROM  mbta_busroutes;

SELECT ST_AsBinary(
 ST_ConvexHull(ST_Collect(geom))
        )
FROM mbta_busroutes ;