DomainTool: Simplify ranged properties discovery

Avoid iterating over all columns known to catalog to then restrict to a
single table by using SQLCatalog API.
Only check for one range column suffix as code anyway relies on the triplet
of columns to be consistently present. Document this in the code and get
rid of now-unneeded range_column_set mechanism.

product/ERP5/Tool/DomainTool.py

@@ -112,14 +112,13 @@ class DomainTool(BaseTool):
       portal_catalog = portal.portal_catalog
       portal_categories = portal.portal_categories
       # Search the columns of the predicate table
-      range_column_set = set()
       query_list = [] if query is None else [query]
-      for column in portal_catalog.getColumnIds():
-        if column[:10] == 'predicate.' and \
-           column[-10:] in ('_range_min', '_range_max'):
-          property_name = column[10:-10]
-          if property_name not in range_column_set:
-            range_column_set.add(property_name)
+      for column in portal_catalog.getSQLCatalog().getTableColumnList('predicate'):
+        # Arbitrary suffix choice, this code expects COLUMN, COLUMN_range_min
+        # and COLUMN_range_max to be simultaneously present for ranged
+        # properties. Only checking one suffix simplifies the code flow.
+        if column.endswith('_range_min'):
+          property_name = column[:-10]
           # We have to check a range property
           equality = 'predicate.' + property_name
           range_min = equality + '_range_min'