diff --git a/pg/sql/0.0.1/05_cdb_union_adjacent.sql b/pg/sql/0.0.1/05_cdb_union_adjacent.sql
new file mode 100644
index 0000000..2450dde
--- /dev/null
+++ b/pg/sql/0.0.1/05_cdb_union_adjacent.sql
@@ -0,0 +1,43 @@
+CREATE OR REPLACE FUNCTION _cdb_final_union_adjacent( joined_geoms geometry[] )
+RETURNS geometry[] AS $$
+BEGIN
+    RETURN joined_geoms;
+END
+$$ LANGUAGE plpgsql;
+
+
+CREATE OR REPLACE FUNCTION _cdb_state_update_union_adjacent(clusters geometry[], new_geom  geometry)
+RETURNS geometry[] AS $$
+DECLARE
+  joins  geometry[] :='{}';
+  unjoined geometry[] :='{}';
+  i integer;
+  combined geometry;
+BEGIN
+  joins := (select array_agg(g)
+            from unnest(clusters) a(g)
+            where ST_TOUCHES(g, new_geom));
+
+  unjoined := (select array_agg(g)
+               from unnest(clusters) a(g)
+               where ST_TOUCHES(g, new_geom) = false);
+
+  IF array_length(joins, 1) > 0 THEN
+    joins := array_append(joins, new_geom);
+    combined := ST_UNION(joins);
+  ELSE
+    combined := new_geom;
+  END IF;
+
+  unjoined := array_append(unjoined, combined);
+  RETURN unjoined;
+END
+$$
+LANGUAGE plpgsql;
+
+CREATE AGGREGATE cdb_union_adjacent(geometry)(
+  SFUNC=_cdb_state_update_union_adjacent,
+  STYPE=geometry[],
+  FINALFUNC=_cdb_final_union_adjacent,
+  INITCOND='{}'
+);
diff --git a/pg/test/0.0.1/expected/05_cdb_union_adjacent_test.out b/pg/test/0.0.1/expected/05_cdb_union_adjacent_test.out
new file mode 100644
index 0000000..21f7ffd
--- /dev/null
+++ b/pg/test/0.0.1/expected/05_cdb_union_adjacent_test.out
@@ -0,0 +1,5 @@
+st_astext
+------------------------------------------------
+POLYGON((1 0,0 0,0 1,0 2,1 2,1 1,2 1,2 0,1 0))
+POLYGON((4 1,4 0,3 0,3 1,3 2,4 2,4 1))
+(2 rows)
diff --git a/pg/test/0.0.1/sql/05_cdb_union_adjacent_test.sql b/pg/test/0.0.1/sql/05_cdb_union_adjacent_test.sql
new file mode 100644
index 0000000..e1adec4
--- /dev/null
+++ b/pg/test/0.0.1/sql/05_cdb_union_adjacent_test.sql
@@ -0,0 +1,9 @@
+\i test/fixtures/touching_polygons.sql
+
+WITH joined_polygons AS (
+  SELECT cdb_union_adjacent(the_geom) the_geom FROM touching_polygons
+),
+unnested_polygons as (
+  select unnest(joined_polygons.the_geom) the_geom from joined_polygons
+)
+select ST_ASTEXT(unnested_polygons.the_geom) from unnested_polygons;
diff --git a/pg/test/fixtures/touching_polygons.sql b/pg/test/fixtures/touching_polygons.sql
new file mode 100644
index 0000000..82c715b
--- /dev/null
+++ b/pg/test/fixtures/touching_polygons.sql
@@ -0,0 +1,8 @@
+-- test table (polygons, some of which touch and some which dont)
+CREATE TABLE touching_polygons(cartodb_id integer, the_geom geometry);
+INSERT INTO  touching_polygons VALUES
+(1, ST_GeomFromText('POLYGON ((0 0, 1 0,1 1, 0 1, 0 0 ))')),
+(2, ST_GeomFromText('POLYGON ((1 0, 2 0, 2 1, 1 1, 1 0))')),
+(1, ST_GeomFromText('POLYGON ((0 1, 1 1,1 2, 0 2, 0 1 ))')),
+(4, ST_GeomFromText('POLYGON ((3 0, 4 0, 4 1, 3 1, 3 0))')),
+(5, ST_GeomFromText('POLYGON ((3 1, 4 1, 4 2, 3 2, 3 1))'));