Add extensive documentation to the ActiveRecord::AbstractAdapter. #2250

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@2371 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

1 files changed, 114 insertions, 18 deletions

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 d7aefc9a82..ea9173039c 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -1,8 +1,10 @@
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
-    # TODO: Document me!
     module SchemaStatements
-      def native_database_types #:nodoc:
+      # Returns a Hash of mappings from the abstract data types to the native
+      # database types.  See TableDefinition#column for details on the recognized
+      # abstract data types.
+      def native_database_types
         {}
       end
 
@@ -11,10 +13,67 @@ module ActiveRecord
       # Returns an array of indexes for the given table.
       # def indexes(table_name, name = nil) end
 
-      # Returns an array of column objects for the table specified by +table_name+.
+      # Returns an array of Column objects for the table specified by +table_name+.
+      # See the concrete implementation for details on the expected parameter values.
       def columns(table_name, name = nil) end
 
-
+      # Creates a new table
+      # There are two ways to work with #create_table.  You can use the block
+      # form or the regular form, like this:
+      #
+      # === Block form
+      #  # create_table() yields a TableDefinition instance
+      #  create_table(:suppliers) do |t|
+      #    t.column :name, :string, :limit => 60
+      #    # Other fields here
+      #  end
+      #
+      # === Regular form
+      #  create_table(:suppliers)
+      #  add_column(:suppliers, :name, :string, {:limit => 60})
+      #
+      # The +options+ hash can include the following keys:
+      # [<tt>:id</tt>]
+      #   Set to true or false to add/not add a primary key column
+      #   automatically.  Defaults to true.
+      # [<tt>:primary_key</tt>]
+      #   The name of the primary key, if one is to be added automatically.
+      #   Defaults to +id+.
+      # [<tt>:options</tt>]
+      #   Any extra options you want appended to the table definition.
+      # [<tt>:temporary</tt>]
+      #   Make a temporary table.
+      #
+      # ===== Examples
+      # ====== Add a backend specific option to the generated SQL (MySQL)
+      #  create_table(:suppliers, :options => 'ENGINE=InnoDB DEFAULT CHARSET=utf8')
+      # generates:
+      #  CREATE TABLE suppliers (
+      #    id int(11) DEFAULT NULL auto_increment PRIMARY KEY
+      #  ) ENGINE=InnoDB DEFAULT CHARSET=utf8
+      #
+      # ====== Rename the primary key column
+      #  create_table(:objects, :primary_key => 'guid') do |t|
+      #    t.column :name, :string, :limit => 80
+      #  end
+      # generates:
+      #  CREATE TABLE objects (
+      #    guid int(11) DEFAULT NULL auto_increment PRIMARY KEY,
+      #    name varchar(80)
+      #  )
+      #
+      # ====== Do not add a primary key column
+      #  create_table(:categories_suppliers, :id => false) do |t|
+      #    t.column :category_id, :integer
+      #    t.column :supplier_id, :integer
+      #  end
+      # generates:
+      #  CREATE TABLE categories_suppliers_join (
+      #    category_id int,
+      #    supplier_id int
+      #  )
+      #
+      # See also TableDefinition#column for details on how to create columns.
       def create_table(name, options = {})
         table_definition = TableDefinition.new(self)
         table_definition.primary_key(options[:primary_key] || "id") unless options[:id] == false
@@ -27,37 +86,71 @@ module ActiveRecord
         execute create_sql
       end
 
+      # Drops a table from the database.
       def drop_table(name)
         execute "DROP TABLE #{name}"
       end
 
+      # Adds a new column to the named table.
+      # See TableDefinition#column for details of the options you can use.
       def add_column(table_name, column_name, type, options = {})
         add_column_sql = "ALTER TABLE #{table_name} ADD #{column_name} #{type_to_sql(type, options[:limit])}"
         add_column_options!(add_column_sql, options)
         execute(add_column_sql)
       end
 
+      # Removes the column from the table definition.
+      # ===== Examples
+      #  remove_column(:suppliers, :qualification)
       def remove_column(table_name, column_name)
         execute "ALTER TABLE #{table_name} DROP #{column_name}"
       end      
 
+      # Changes the column's definition according to the new options.
+      # See TableDefinition#column for details of the options you can use.
+      # ===== Examples
+      #  change_column(:suppliers, :name, :string, :limit => 80)
+      #  change_column(:accounts, :description, :text)
       def change_column(table_name, column_name, type, options = {})
         raise NotImplementedError, "change_column is not implemented"
       end
 
+      # Sets a new default value for a column.  If you want to set the default
+      # value to +NULL+, you are out of luck.  You need to
+      # DatabaseStatements#execute the apppropriate SQL statement yourself.
+      # ===== Examples
+      #  change_column_default(:suppliers, :qualification, 'new')
+      #  change_column_default(:accounts, :authorized, 1)
       def change_column_default(table_name, column_name, default)
         raise NotImplementedError, "change_column_default is not implemented"
       end
 
+      # Renames a column.
+      # ===== Example
+      #  rename_column(:suppliers, :description, :name)
       def rename_column(table_name, column_name, new_column_name)
         raise NotImplementedError, "rename_column is not implemented"
       end
 
-      # Create a new index on the given table. By default, it will be named
-      # <code>"#{table_name}_#{Array(column_name).first}_index"</code>, but you
-      # can explicitly name the index by passing <code>:name => "..."</code>
-      # as the last parameter. Unique indexes may be created by passing
-      # <code>:unique => true</code>.
+      # Adds a new index to the table.  +column_name+ can be a single Symbol, or
+      # an Array of Symbols.
+      #
+      # The index will be named after the table and the first column names,
+      # unless you pass +:name+ as an option.
+      #
+      # ===== Examples
+      # ====== Creating a simple index
+      #  add_index(:suppliers, :name)
+      # generates
+      #  CREATE INDEX suppliers_name_index ON suppliers(name)
+      # ====== Creating a unique index
+      #  add_index(:accounts, [:branch_id, :party_id], :unique => true)
+      # generates
+      #  CREATE UNIQUE INDEX accounts_branch_id_index ON accounts(branch_id, party_id)
+      # ====== Creating a named index
+      #  add_index(:accounts, [:branch_id, :party_id], :unique => true, :name => 'by_branch_party')
+      # generates
+      #  CREATE UNIQUE INDEX by_branch_party ON accounts(branch_id, party_id)
       def add_index(table_name, column_name, options = {})
         index_name = "#{table_name}_#{Array(column_name).first}_index"
 
@@ -73,12 +166,12 @@ module ActiveRecord
 
       # Remove the given index from the table.
       #
-      #   remove_index :my_table, :column => :foo
-      #   remove_index :my_table, :name => :my_index_on_foo
-      #
-      # The first version will remove the index named
-      # <code>"#{my_table}_#{column}_index"</code> from the table. The
-      # second removes the named column from the table.
+      # Remove the suppliers_name_index in the suppliers table (legacy support, use the second or third forms).
+      #   remove_index :suppliers, :name
+      # Remove the index named accounts_branch_id in the accounts table.
+      #   remove_index :accounts, :column => :branch_id
+      # Remove the index named by_branch_party in the accounts table.
+      #   remove_index :accounts, :name => :by_branch_party
       def remove_index(table_name, options = {})
         if Hash === options # legacy support
           if options[:column]
@@ -96,11 +189,14 @@ module ActiveRecord
       end
 
 
-      # Returns a string of the CREATE TABLE SQL statements for recreating the entire structure of the database.
-      def structure_dump #:nodoc:
+      # Returns a string of <tt>CREATE TABLE</tt> SQL statement(s) for recreating the
+      # entire structure of the database.
+      def structure_dump
       end
 
-      def initialize_schema_information #:nodoc:
+      # Should not be called normally, but this operation is non-destructive.
+      # The migrations module handles this automatically.
+      def initialize_schema_information
         begin
           execute "CREATE TABLE #{ActiveRecord::Migrator.schema_info_table_name} (version #{type_to_sql(:integer)})"
           execute "INSERT INTO #{ActiveRecord::Migrator.schema_info_table_name} (version) VALUES(0)"