make add_index and remove_index more resilient; new rename_index method; track database limits

[#3452 state:committed]

Signed-off-by: Jeremy Kemper <jeremy@bitsweat.net>

1 files changed, 57 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_limits.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_limits.rb
new file mode 100644
index 0000000000..4118ea7b31
--- /dev/null
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_limits.rb
@@ -0,0 +1,57 @@
+module ActiveRecord
+  module ConnectionAdapters # :nodoc:
+    module DatabaseLimits
+
+      # the maximum length of a table alias
+      def table_alias_length
+        255
+      end
+
+      # the maximum length of a column name
+      def column_name_length
+        64
+      end
+
+      # the maximum length of a table name
+      def table_name_length
+        64
+      end
+
+      # the maximum length of an index name
+      def index_name_length
+        64
+      end
+
+      # the maximum number of columns per table
+      def columns_per_table
+        1024
+      end
+
+      # the maximum number of indexes per table
+      def indexes_per_table
+        16
+      end
+
+      # the maximum number of columns in a multicolumn index
+      def columns_per_multicolumn_index
+        16
+      end
+
+      # the maximum number of elements in an IN (x,y,z) clause
+      def in_clause_length
+        65535
+      end
+
+      # the maximum length of a SQL query
+      def sql_query_length
+        1048575
+      end
+
+      # maximum number of joins in a single query
+      def joins_per_query
+        256
+      end
+
+    end
+  end
+end