TECH-4995: generalize rails_4 exception to sqlite

Author: ColinDKelley

lib/declare_schema/model/index_definition.rb

@@ -37,7 +37,7 @@ class << self
         def for_model(model, old_table_name = nil)
           t = old_table_name || model.table_name
 
-          primary_key_columns = Array(model.connection.primary_key(t)).presence || rails_4_compound_primary_key(model, t) or
+          primary_key_columns = Array(model.connection.primary_key(t)).presence || sqlite_compound_primary_key(model, t) or
             raise "could not find primary key for table #{t} in #{model.connection.columns(t).inspect}"
 
           primary_key_found = false
@@ -62,9 +62,9 @@ def for_model(model, old_table_name = nil)
 
         private
 
-        # This is the old approach for Rails 4. Delete it when we drop support!
-        def rails_4_compound_primary_key(model, table)
-          Rails::VERSION::MAJOR >= 5 and return nil
+        # This is the old approach which is still needed for SQLite, at least through Rails 5
+        def sqlite_compound_primary_key(model, table)
+          !ActiveRecord::Base.connection.class.name.match?(/SQLite3Adapter/) || Rails::VERSION::MAJOR > 5 and return nil
 
           connection = model.connection.dup