diff -r 058bb3dc685f -r 0b59724cb3f2 cubicweb/server/test/data-migractions/cubes/fakecustomtype/site_cubicweb.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cubicweb/server/test/data-migractions/cubes/fakecustomtype/site_cubicweb.py	Sat Jan 16 13:48:51 2016 +0100
@@ -0,0 +1,17 @@
+from yams import register_base_type
+from logilab.database import get_db_helper
+from logilab.database.sqlgen import SQLExpression
+
+_NUMERIC_PARAMETERS = {'scale': 0, 'precision': None}
+register_base_type('Numeric', _NUMERIC_PARAMETERS)
+
+# Add the datatype to the helper mapping
+pghelper = get_db_helper('postgres')
+
+
+def pg_numeric_sqltype(rdef):
+    """Return a PostgreSQL column type corresponding to rdef
+    """
+    return 'numeric(%s, %s)' % (rdef.precision, rdef.scale)
+
+pghelper.TYPE_MAPPING['Numeric'] = pg_numeric_sqltype