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>

5 files changed, 106 insertions, 11 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
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index 1255ef09be..d3499cea72 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -10,11 +10,6 @@ module ActiveRecord
         {}
       end
 
-      # This is the maximum length a table alias can be
-      def table_alias_length
-        255
-      end
-
       # Truncates a table alias according to the limits of the current adapter.
       def table_alias_for(table_name)
         table_name[0..table_alias_length-1].gsub(/\./, '_')
@@ -293,6 +288,14 @@ module ActiveRecord
           index_type = options
         end
 
+        if index_name.length > index_name_length
+          @logger.warn("Index name '#{index_name}' on table '#{table_name}' is too long; the limit is #{index_name_length} characters. Skipping.")
+          return
+        end
+        if index_exists?(table_name, index_name, false)
+          @logger.warn("Index name '#{index_name}' on table '#{table_name}' already exists. Skipping.")
+          return
+        end
         quoted_column_names = quoted_columns_for_index(column_names, options).join(", ")
 
         execute "CREATE #{index_type} INDEX #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} (#{quoted_column_names})"
@@ -309,7 +312,28 @@ module ActiveRecord
       # Remove the index named by_branch_party in the accounts table.
       #   remove_index :accounts, :name => :by_branch_party
       def remove_index(table_name, options = {})
-        execute "DROP INDEX #{quote_column_name(index_name(table_name, options))} ON #{quote_table_name(table_name)}"
+        index_name = index_name(table_name, options)
+        unless index_exists?(table_name, index_name, true)
+          @logger.warn("Index name '#{index_name}' on table '#{table_name}' does not exist. Skipping.")
+          return
+        end
+        remove_index!(table_name, index_name)
+      end
+
+      def remove_index!(table_name, index_name) #:nodoc:
+        execute "DROP INDEX #{quote_column_name(index_name)} ON #{table_name}"
+      end
+
+      # Rename an index.
+      #
+      # Rename the index_people_on_last_name index to index_users_on_last_name
+      #   rename_index :people, 'index_people_on_last_name', 'index_users_on_last_name'
+      def rename_index(table_name, old_name, new_name)
+        # this is a naive implementation; some DBs may support this more efficiently (Postgres, for instance)
+        old_index_def = indexes(table_name).detect { |i| i.name == old_name }
+        return unless old_index_def
+        remove_index(table_name, :name => old_name)
+        add_index(table_name, old_index_def.columns, :name => new_name, :unique => old_index_def.unique)
       end
 
       def index_name(table_name, options) #:nodoc:
@@ -326,6 +350,15 @@ module ActiveRecord
         end
       end
 
+      # Verify the existence of an index.
+      #
+      # The default argument is returned if the underlying implementation does not define the indexes method,
+      # as there's no way to determine the correct answer in that case.
+      def index_exists?(table_name, index_name, default)
+        return default unless respond_to?(:indexes)
+        indexes(table_name).detect { |i| i.name == index_name }
+      end
+
       # Returns a string of <tt>CREATE TABLE</tt> SQL statement(s) for recreating the
       # entire structure of the database.
       def structure_dump
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 28a59c1e62..fecd4d590e 100755
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -11,6 +11,7 @@ require 'active_record/connection_adapters/abstract/quoting'
 require 'active_record/connection_adapters/abstract/connection_pool'
 require 'active_record/connection_adapters/abstract/connection_specification'
 require 'active_record/connection_adapters/abstract/query_cache'
+require 'active_record/connection_adapters/abstract/database_limits'
 
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
@@ -29,6 +30,7 @@ module ActiveRecord
     # notably, the instance methods provided by SchemaStatement are very useful.
     class AbstractAdapter
       include Quoting, DatabaseStatements, SchemaStatements
+      include DatabaseLimits
       include QueryCache
       include ActiveSupport::Callbacks
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 6389094b8a..34aaff2b49 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -819,9 +819,12 @@ module ActiveRecord
         execute "ALTER TABLE #{quote_table_name(table_name)} RENAME COLUMN #{quote_column_name(column_name)} TO #{quote_column_name(new_column_name)}"
       end
 
-      # Drops an index from a table.
-      def remove_index(table_name, options = {})
-        execute "DROP INDEX #{quote_table_name(index_name(table_name, options))}"
+      def remove_index!(table_name, index_name) #:nodoc:
+        execute "DROP INDEX #{quote_table_name(index_name)}"
+      end
+
+      def index_name_length
+        63
       end
 
       # Maps logical Rails types to PostgreSQL-specific data types.
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
index 29225b83c5..e8a45bb3c6 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
@@ -217,8 +217,8 @@ module ActiveRecord
         column ? column['name'] : nil
       end
 
-      def remove_index(table_name, options={}) #:nodoc:
-        execute "DROP INDEX #{quote_column_name(index_name(table_name, options))}"
+      def remove_index!(table_name, index_name) #:nodoc:
+        execute "DROP INDEX #{quote_column_name(index_name)}"
       end
 
       def rename_table(name, new_name)