#434

backend/app/services/counts_pivot_totals.rb

@@ -19,7 +19,9 @@ class CountsPivotTotals
             (0...column_depth).map { @axes.rows.length + _1 }
         expressions = indexes.map { @axes.expressions[_1] }
         scope = @population.scope.except(:select, :order, :where, :from).from('authorised v')
-        joins = @axes.joins(indexes.map { @axes.all[_1].fetch('field') })
+        additive = @axes.rows.any? { _1['field'] == 'tags' }
+        retained = additive ? (0...@axes.rows.length).to_a | indexes : indexes
+        joins = @axes.joins(retained.map { @axes.all[_1].fetch('field') })
         scope = scope.joins(joins) unless joins.empty?
         if row_depth.positive?
           tuples = headers.map { _1[:values] }.uniq
@@ -42,9 +44,23 @@ class CountsPivotTotals
         padding = (expressions.length...@axes.all.length).map { "NULL AS v#{ _1 }" }
         fields = ["#{ row_depth } AS row_depth", "#{ column_depth } AS column_depth"] +
             grouped + padding + ['COUNT(DISTINCT v.id) AS count']
-        scope = scope.group(*expressions.map { Arel.sql(_1) }) if expressions.any?
-        scope.optimizer_hints('MAX_EXECUTION_TIME(10000)')
-            .select(Arel.sql(fields.join(', '))).to_sql
+        if additive
+          # Sum full row tuples, not page cells; preserve DISTINCT inside each tuple.
+          leaf = retained.map { @axes.expressions[_1] }
+          selected = leaf.each_with_index.map { |expression, index| "#{ expression } AS k#{ index }" }
+          inner = scope.group(*leaf.map { Arel.sql(_1) })
+              .select(Arel.sql((selected + ['COUNT(DISTINCT v.id) AS count']).join(', '))).to_sql
+          coordinates = indexes.map { "k#{ retained.index(_1) }" }
+          projected = coordinates.each_with_index.map { |key, index| "#{ key } AS v#{ index }" }
+          output = ["#{ row_depth } AS row_depth", "#{ column_depth } AS column_depth"] +
+              projected + padding + ['SUM(count) AS count']
+          grouping = coordinates.empty? ? '' : " GROUP BY #{ coordinates.join(', ') }"
+          "SELECT #{ output.join(', ') } FROM (#{ inner }) leaf#{ grouping }"
+        else
+          scope = scope.group(*expressions.map { Arel.sql(_1) }) if expressions.any?
+          scope.optimizer_hints('MAX_EXECUTION_TIME(10000)')
+              .select(Arel.sql(fields.join(', '))).to_sql
+        end
       end
     end
     return [] if queries.empty?