mlitwiniuk · December 4, 2017 17:10 · Dec 4, 2017
diff --git a/rails_4_2_postgres_10_sequence_monkey_patch_fix.rb b/rails_4_2_postgres_10_sequence_monkey_patch_fix.rb
@@ -0,0 +1,42 @@
+# In PostgreSQL 10 each sequence does not know `increment_by` or `min_value`
+# This fix is already in Rails master, this is just monkey patch "to make it
+# work" in Rails 4.2
+# More details here: https://github.com/rails/rails/pull/28864
+# Original issue: https://github.com/rails/rails/issues/28780
+module ActiveRecord
+  module ConnectionAdapters
+    module PostgreSQL
+      module SchemaStatements
+        # Resets the sequence of a table's primary key to the maximum value.
+        def reset_pk_sequence!(table, pk = nil, sequence = nil) #:nodoc:
+          unless pk && sequence
+            default_pk, default_sequence = pk_and_sequence_for(table)
+
+            pk ||= default_pk
+            sequence ||= default_sequence
+          end
+
+          if @logger && pk && !sequence
+            @logger.warn "#{table} has primary key #{pk} with no default sequence."
+          end
+
+          if pk && sequence
+            quoted_sequence = quote_table_name(sequence)
+            max_pk = select_value("select MAX(#{quote_column_name pk}) from #{quote_table_name(table)}")
+            if max_pk.nil?
+              if postgresql_version >= 100000
+                minvalue = select_value("SELECT seqmin from pg_sequence where seqrelid = '#{quoted_sequence}'::regclass")
+              else
+                minvalue = select_value("SELECT min_value FROM #{quoted_sequence}")
+              end
+            end
+
+            select_value(<<-end_sql, "SCHEMA")
+              SELECT setval('#{quoted_sequence}', #{max_pk ? max_pk : minvalue}, #{max_pk ? true : false})
+            end_sql
+          end
+        end
+      end
+    end
+  end
+end
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