Answer by Tamas Kosa for PostGIS polygon edge analysis (orientation, edge length)

Yesterday I had no time to create it in details... See my solution in 4 steps:

CREATE OR REPLACE VIEW bd_segment ASSELECT      ST_PointN(geom, generate_series(1, ST_NPoints(geom)-1)) AS sp,      ST_PointN(geom, generate_series(2, ST_NPoints(geom)  )) AS ep    FROM       -- extract the individual linestrings       (SELECT (ST_Dump(ST_Boundary(the_geom))).geom       FROM bd) AS linestrings;CREATE OR REPLACE VIEW bd_segment_geom ASSELECT sp, ep, st_makeline(sp, ep) FROM bd_segment;CREATE OR REPLACE view bd_segment_id AS SELECT bd.gid, row_number()     OVER (order by bd.gid), degrees(st_azimuth(ff.sp, ff.ep)-1.57079633) AS az_deg,    ST_LENGTH(ff.st_makeline) , ff.st_makeline FROM bd_segment_geom ffJOIN bd ON st_touches(ff.st_makeline, bd.the_geom)GROUP BY bd.gid, ff.sp, ff.ep, ff.st_makeline;UPDATE bd_segment_idSET az_deg = az_deg + 360WHERE az_deg < 0;

The last query give you the building ids with a spatial join using st_touches. Hope it helps.Update - In qgis the solution looks like this: