Do not calculate values if they are not going to be used

When building the indexes list in PostgreSQL, IndexDefinition objects
are only created if the query for the related attributes really returns
something matching the attributes.

In case it does not, the variables for building the definition objects were
being created but not used.

1 files changed, 9 insertions, 7 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index 0168c36abc..d9b807bba4 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -156,13 +156,15 @@ module ActiveRecord
 
             column_names = columns.values_at(*indkey).compact
 
-            # add info on sort order for columns (only desc order is explicitly specified, asc is the default)
-            desc_order_columns = inddef.scan(/(\w+) DESC/).flatten
-            orders = desc_order_columns.any? ? Hash[desc_order_columns.map {|order_column| [order_column, :desc]}] : {}
-            where = inddef.scan(/WHERE (.+)$/).flatten[0]
-            using = inddef.scan(/USING (.+?) /).flatten[0].to_sym
-
-            column_names.empty? ? nil : IndexDefinition.new(table_name, index_name, unique, column_names, [], orders, where, nil, using)
+            unless column_names.empty?
+              # add info on sort order for columns (only desc order is explicitly specified, asc is the default)
+              desc_order_columns = inddef.scan(/(\w+) DESC/).flatten
+              orders = desc_order_columns.any? ? Hash[desc_order_columns.map {|order_column| [order_column, :desc]}] : {}
+              where = inddef.scan(/WHERE (.+)$/).flatten[0]
+              using = inddef.scan(/USING (.+?) /).flatten[0].to_sym
+
+              IndexDefinition.new(table_name, index_name, unique, column_names, [], orders, where, nil, using)
+            end
           end.compact
         end