Module: ActiveRecord::ConnectionAdapters::SchemaStatements

Module

ActiveRecord::ConnectionAdapters::SchemaStatements

In:

vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb

Public Instance methods

add_column(table_name, column_name, type, options = {})

Adds a new column to the named table. See TableDefinition#column for details of the options you can use.

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 192
192:       def add_column(table_name, column_name, type, options = {})
193:         add_column_sql = "ALTER TABLE #{quote_table_name(table_name)} ADD #{quote_column_name(column_name)} #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
194:         add_column_options!(add_column_sql, options)
195:         execute(add_column_sql)
196:       end

add_index(table_name, column_name, options = {})

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 name, unless you pass :name as an option.

When creating an index on multiple columns, the first column is used as a name for the index. For example, when you specify an index on two columns [:first, :last], the DBMS creates an index for both columns as well as an index for the first column :first. Using just the first name for this index makes sense, because you will never have to create a singular index with this name.

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_party_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)

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 261
261:       def add_index(table_name, column_name, options = {})
262:         column_names = Array(column_name)
263:         index_name   = index_name(table_name, :column => column_names)
264: 
265:         if Hash === options # legacy support, since this param was a string
266:           index_type = options[:unique] ? "UNIQUE" : ""
267:           index_name = options[:name] || index_name
268:         else
269:           index_type = options
270:         end
271:         quoted_column_names = column_names.map { |e| quote_column_name(e) }.join(", ")
272:         execute "CREATE #{index_type} INDEX #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} (#{quoted_column_names})"
273:       end

add_order_by_for_association_limiting!(sql, options)

ORDER BY clause for the passed order option. PostgreSQL overrides this due to its stricter standards compliance.

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 408
408:       def add_order_by_for_association_limiting!(sql, options)
409:         sql << " ORDER BY #{options[:order]}"
410:       end

add_timestamps(table_name)

Adds timestamps (created_at and updated_at) columns to the named table.

Examples

 add_timestamps(:suppliers)

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 415
415:       def add_timestamps(table_name)
416:         add_column table_name, :created_at, :datetime
417:         add_column table_name, :updated_at, :datetime
418:       end

assume_migrated_upto_version(version)

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 339
339:       def assume_migrated_upto_version(version)
340:         version = version.to_i
341:         sm_table = quote_table_name(ActiveRecord::Migrator.schema_migrations_table_name)
342: 
343:         migrated = select_values("SELECT version FROM #{sm_table}").map(&:to_i)
344:         versions = Dir['db/migrate/[0-9]*_*.rb'].map do |filename|
345:           filename.split('/').last.split('_').first.to_i
346:         end
347: 
348:         unless migrated.include?(version)
349:           execute "INSERT INTO #{sm_table} (version) VALUES ('#{version}')"
350:         end
351: 
352:         inserted = Set.new
353:         (versions - migrated).each do |v|
354:           if inserted.include?(v)
355:             raise "Duplicate migration #{v}. Please renumber your migrations to resolve the conflict."
356:           elsif v < version
357:             execute "INSERT INTO #{sm_table} (version) VALUES ('#{v}')"
358:             inserted << v
359:           end
360:         end
361:       end

change_column(table_name, column_name, type, options = {})

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)

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 214
214:       def change_column(table_name, column_name, type, options = {})
215:         raise NotImplementedError, "change_column is not implemented"
216:       end

change_column_default(table_name, column_name, default)

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 appropriate SQL statement yourself.

Examples

 change_column_default(:suppliers, :qualification, 'new')
 change_column_default(:accounts, :authorized, 1)

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 224
224:       def change_column_default(table_name, column_name, default)
225:         raise NotImplementedError, "change_column_default is not implemented"
226:       end

change_table(table_name) {|Table.new(table_name, self)| ...}

A block for changing columns in table.

Example

 # change_table() yields a Table instance
 change_table(:suppliers) do |t|
   t.column :name, :string, :limit => 60
   # Other column alterations here
 end

Examples

Add a column

 change_table(:suppliers) do |t|
   t.column :name, :string, :limit => 60
 end

Add 2 integer columns

 change_table(:suppliers) do |t|
   t.integer :width, :height, :null => false, :default => 0
 end

Add created_at/updated_at columns

 change_table(:suppliers) do |t|
   t.timestamps
 end

Add a foreign key column

 change_table(:suppliers) do |t|
   t.references :company
 end

Creates a company_id(integer) column

Add a polymorphic foreign key column

 change_table(:suppliers) do |t|
   t.belongs_to :company, :polymorphic => true
 end

Creates company_type(varchar) and company_id(integer) columns

Remove a column

 change_table(:suppliers) do |t|
   t.remove :company
 end

Remove several columns

 change_table(:suppliers) do |t|
   t.remove :company_id
   t.remove :width, :height
 end

Remove an index

 change_table(:suppliers) do |t|
   t.remove_index :company_id
 end

See also Table for details on all of the various column transformation

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 174
174:       def change_table(table_name)
175:         yield Table.new(table_name, self)
176:       end

columns(table_name, name = nil)

Returns an array of Column objects for the table specified by table_name. See the concrete implementation for details on the expected parameter values.

    # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 32
32:       def columns(table_name, name = nil) end

create_table(table_name, options = {}) {|table_definition| ...}

Creates a new table with the name table_name. table_name may either be a String or a Symbol.

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() passes a TableDefinition object to the block.
 # This form will not only create the table, but also columns for the
 # table.
 create_table(:suppliers) do |t|
   t.column :name, :string, :limit => 60
   # Other fields here
 end

Regular form

 # Creates a table called 'suppliers' with no columns.
 create_table(:suppliers)
 # Add a column to 'suppliers'.
 add_column(:suppliers, :name, :string, {:limit => 60})

The options hash can include the following keys:

:id: Whether to automatically add a primary key column. Defaults to true. Join tables for has_and_belongs_to_many should set :id => false.
:primary_key: The name of the primary key, if one is to be added automatically. Defaults to id.
:options: Any extra options you want appended to the table definition.
:temporary: Make a temporary table.
:force: Set to true to drop the table before creating it. Defaults to false.

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 (
   category_id int,
   supplier_id int
 )

See also TableDefinition#column for details on how to create columns.

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 100
100:       def create_table(table_name, options = {})
101:         table_definition = TableDefinition.new(self)
102:         table_definition.primary_key(options[:primary_key] || Base.get_primary_key(table_name.to_s.singularize)) unless options[:id] == false
103: 
104:         yield table_definition
105: 
106:         if options[:force] && table_exists?(table_name)
107:           drop_table(table_name, options)
108:         end
109: 
110:         create_sql = "CREATE#{' TEMPORARY' if options[:temporary]} TABLE "
111:         create_sql << "#{quote_table_name(table_name)} ("
112:         create_sql << table_definition.to_sql
113:         create_sql << ") #{options[:options]}"
114:         execute create_sql
115:       end

distinct(columns, order_by)

SELECT DISTINCT clause for a given set of columns and a given ORDER BY clause. Both PostgreSQL and Oracle overrides this for custom DISTINCT syntax.

  distinct("posts.id", "posts.created_at desc")

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 402
402:       def distinct(columns, order_by)
403:         "DISTINCT #{columns}"
404:       end

drop_table(table_name, options = {})

Drops a table from the database.

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 186
186:       def drop_table(table_name, options = {})
187:         execute "DROP TABLE #{quote_table_name(table_name)}"
188:       end

initialize_schema_migrations_table()

Should not be called normally, but this operation is non-destructive. The migrations module handles this automatically.

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 316
316:       def initialize_schema_migrations_table
317:         sm_table = ActiveRecord::Migrator.schema_migrations_table_name
318: 
319:         unless tables.detect { |t| t == sm_table }
320:           create_table(sm_table, :id => false) do |schema_migrations_table|
321:             schema_migrations_table.column :version, :string, :null => false
322:           end
323:           add_index sm_table, :version, :unique => true,
324:             :name => "#{Base.table_name_prefix}unique_schema_migrations#{Base.table_name_suffix}"
325: 
326:           # Backwards-compatibility: if we find schema_info, assume we've
327:           # migrated up to that point:
328:           si_table = Base.table_name_prefix + 'schema_info' + Base.table_name_suffix
329: 
330:           if tables.detect { |t| t == si_table }
331: 
332:             old_version = select_value("SELECT version FROM #{quote_table_name(si_table)}").to_i
333:             assume_migrated_upto_version(old_version)
334:             drop_table(si_table)
335:           end
336:         end
337:       end

native_database_types()

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.

   # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 7
7:       def native_database_types
8:         {}
9:       end

remove_column(table_name, *column_names)

Removes the column(s) from the table definition.

Examples

 remove_column(:suppliers, :qualification)
 remove_columns(:suppliers, :qualification, :experience)

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 202
202:       def remove_column(table_name, *column_names)
203:         column_names.flatten.each do |column_name|
204:           execute "ALTER TABLE #{quote_table_name(table_name)} DROP #{quote_column_name(column_name)}"
205:         end
206:       end

remove_columns(table_name, *column_names)

Alias for remove_column

remove_index(table_name, options = {})

Remove the given index from the table.

Remove the suppliers_name_index in the suppliers table.

  remove_index :suppliers, :name

Remove the index named accounts_branch_id_index in the accounts table.

  remove_index :accounts, :column => :branch_id

Remove the index named accounts_branch_id_party_id_index in the accounts table.

  remove_index :accounts, :column => [:branch_id, :party_id]

Remove the index named by_branch_party in the accounts table.

  remove_index :accounts, :name => :by_branch_party

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 285
285:       def remove_index(table_name, options = {})
286:         execute "DROP INDEX #{quote_column_name(index_name(table_name, options))} ON #{table_name}"
287:       end

remove_timestamps(table_name)

Removes the timestamp columns (created_at and updated_at) from the table definition.

Examples

 remove_timestamps(:suppliers)

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 423
423:       def remove_timestamps(table_name)
424:         remove_column table_name, :updated_at
425:         remove_column table_name, :created_at
426:       end

rename_column(table_name, column_name, new_column_name)

Renames a column.

Example

 rename_column(:suppliers, :description, :name)

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 231
231:       def rename_column(table_name, column_name, new_column_name)
232:         raise NotImplementedError, "rename_column is not implemented"
233:       end

rename_table(table_name, new_name)

Renames a table.

Example

 rename_table('octopuses', 'octopi')

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 181
181:       def rename_table(table_name, new_name)
182:         raise NotImplementedError, "rename_table is not implemented"
183:       end

structure_dump()

Returns a string of CREATE TABLE SQL statement(s) for recreating the entire structure of the database.

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 305
305:       def structure_dump
306:       end

table_alias_for(table_name)

Truncates a table alias according to the limits of the current adapter.

    # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 17
17:       def table_alias_for(table_name)
18:         table_name[0..table_alias_length-1].gsub(/\./, '_')
19:       end

table_alias_length()

This is the maximum length a table alias can be

    # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 12
12:       def table_alias_length
13:         255
14:       end

table_exists?(table_name)

def tables(name = nil) end

    # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 23
23:       def table_exists?(table_name)
24:         tables.include?(table_name.to_s)
25:       end

Protected Instance methods

options_include_default?(options)

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 429
429:         def options_include_default?(options)
430:           options.include?(:default) && !(options[:null] == false && options[:default].nil?)
431:         end