- add_column
- add_index
- add_order_by_for_association_limiting!
- add_timestamps
- assume_migrated_upto_version
- change_column
- change_column_default
- change_table
- columns
- create_table
- distinct
- drop_table
- index_exists?
- initialize_schema_migrations_table
- native_database_types
- options_include_default?
- quoted_columns_for_index
- remove_column
- remove_columns
- remove_index
- remove_timestamps
- rename_column
- rename_index
- rename_table
- structure_dump
- table_alias_for
- table_exists?
Adds a new column to the named table. See TableDefinition#column for details of the options you can use.
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 187 187: def add_column(table_name, column_name, type, options = {}) 188: 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])}" 189: add_column_options!(add_column_sql, options) 190: execute(add_column_sql) 191: end
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)
Creating an index with specific key length
add_index(:accounts, :name, :name => 'by_name', :length => 10)
generates
CREATE INDEX by_name ON accounts(name(10)) add_index(:accounts, [:name, :surname], :name => 'by_name_surname', :length => {:name => 10, :surname => 15})
generates
CREATE INDEX by_name_surname ON accounts(name(10), surname(15))
Note: SQLite doesn‘t support index length
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 270 270: def add_index(table_name, column_name, options = {}) 271: column_names = Array(column_name) 272: index_name = index_name(table_name, :column => column_names) 273: 274: if Hash === options # legacy support, since this param was a string 275: index_type = options[:unique] ? "UNIQUE" : "" 276: index_name = options[:name] || index_name 277: else 278: index_type = options 279: end 280: 281: if index_name.length > index_name_length 282: @logger.warn("Index name '#{index_name}' on table '#{table_name}' is too long; the limit is #{index_name_length} characters. Skipping.") 283: return 284: end 285: if index_exists?(table_name, index_name, false) 286: @logger.warn("Index name '#{index_name}' on table '#{table_name}' already exists. Skipping.") 287: return 288: end 289: quoted_column_names = quoted_columns_for_index(column_names, options).join(", ") 290: 291: execute "CREATE #{index_type} INDEX #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} (#{quoted_column_names})" 292: end
ORDER BY clause for the passed order option. PostgreSQL overrides this due to its stricter standards compliance.
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 457 457: def add_order_by_for_association_limiting!(sql, options) 458: sql << " ORDER BY #{options[:order]}" 459: end
Adds timestamps (created_at and updated_at) columns to the named table.
Examples
add_timestamps(:suppliers)
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 464 464: def add_timestamps(table_name) 465: add_column table_name, :created_at, :datetime 466: add_column table_name, :updated_at, :datetime 467: end
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 388 388: def assume_migrated_upto_version(version, migrations_path = ActiveRecord::Migrator.migrations_path) 389: version = version.to_i 390: sm_table = quote_table_name(ActiveRecord::Migrator.schema_migrations_table_name) 391: 392: migrated = select_values("SELECT version FROM #{sm_table}").map(&:to_i) 393: versions = Dir["#{migrations_path}/[0-9]*_*.rb"].map do |filename| 394: filename.split('/').last.split('_').first.to_i 395: end 396: 397: unless migrated.include?(version) 398: execute "INSERT INTO #{sm_table} (version) VALUES ('#{version}')" 399: end 400: 401: inserted = Set.new 402: (versions - migrated).each do |v| 403: if inserted.include?(v) 404: raise "Duplicate migration #{v}. Please renumber your migrations to resolve the conflict." 405: elsif v < version 406: execute "INSERT INTO #{sm_table} (version) VALUES ('#{v}')" 407: inserted << v 408: end 409: end 410: 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)
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 209 209: def change_column(table_name, column_name, type, options = {}) 210: raise NotImplementedError, "change_column is not implemented" 211: 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 appropriate SQL statement yourself.
Examples
change_column_default(:suppliers, :qualification, 'new') change_column_default(:accounts, :authorized, 1)
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 219 219: def change_column_default(table_name, column_name, default) 220: raise NotImplementedError, "change_column_default is not implemented" 221: end
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
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 169 169: def change_table(table_name) 170: yield Table.new(table_name, self) 171: end
Returns an array of Column objects for the table specified by table_name. See the concrete implementation for details on the expected parameter values.
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 27 27: def columns(table_name, name = nil) end
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.
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 95 95: def create_table(table_name, options = {}) 96: table_definition = TableDefinition.new(self) 97: table_definition.primary_key(options[:primary_key] || Base.get_primary_key(table_name.to_s.singularize)) unless options[:id] == false 98: 99: yield table_definition if block_given? 100: 101: if options[:force] && table_exists?(table_name) 102: drop_table(table_name, options) 103: end 104: 105: create_sql = "CREATE#{' TEMPORARY' if options[:temporary]} TABLE " 106: create_sql << "#{quote_table_name(table_name)} (" 107: create_sql << table_definition.to_sql 108: create_sql << ") #{options[:options]}" 109: execute create_sql 110: end
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")
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 451 451: def distinct(columns, order_by) 452: "DISTINCT #{columns}" 453: end
Drops a table from the database.
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 181 181: def drop_table(table_name, options = {}) 182: execute "DROP TABLE #{quote_table_name(table_name)}" 183: 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.
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 347 347: def index_exists?(table_name, index_name, default) 348: return default unless respond_to?(:indexes) 349: indexes(table_name).detect { |i| i.name == index_name } 350: end
Should not be called normally, but this operation is non-destructive. The migrations module handles this automatically.
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 365 365: def initialize_schema_migrations_table 366: sm_table = ActiveRecord::Migrator.schema_migrations_table_name 367: 368: unless tables.detect { |t| t == sm_table } 369: create_table(sm_table, :id => false) do |schema_migrations_table| 370: schema_migrations_table.column :version, :string, :null => false 371: end 372: add_index sm_table, :version, :unique => true, 373: :name => "#{Base.table_name_prefix}unique_schema_migrations#{Base.table_name_suffix}" 374: 375: # Backwards-compatibility: if we find schema_info, assume we've 376: # migrated up to that point: 377: si_table = Base.table_name_prefix + 'schema_info' + Base.table_name_suffix 378: 379: if tables.detect { |t| t == si_table } 380: 381: old_version = select_value("SELECT version FROM #{quote_table_name(si_table)}").to_i 382: assume_migrated_upto_version(old_version) 383: drop_table(si_table) 384: end 385: end 386: end
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.
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 7 7: def native_database_types 8: {} 9: end
Removes the column(s) from the table definition.
Examples
remove_column(:suppliers, :qualification) remove_columns(:suppliers, :qualification, :experience)
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 197 197: def remove_column(table_name, *column_names) 198: column_names.flatten.each do |column_name| 199: execute "ALTER TABLE #{quote_table_name(table_name)} DROP #{quote_column_name(column_name)}" 200: end 201: end
Alias for remove_column
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
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 304 304: def remove_index(table_name, options = {}) 305: index_name = index_name(table_name, options) 306: unless index_exists?(table_name, index_name, true) 307: @logger.warn("Index name '#{index_name}' on table '#{table_name}' does not exist. Skipping.") 308: return 309: end 310: remove_index!(table_name, index_name) 311: end
Removes the timestamp columns (created_at and updated_at) from the table definition.
Examples
remove_timestamps(:suppliers)
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 472 472: def remove_timestamps(table_name) 473: remove_column table_name, :updated_at 474: remove_column table_name, :created_at 475: end
Renames a column.
Example
rename_column(:suppliers, :description, :name)
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 226 226: def rename_column(table_name, column_name, new_column_name) 227: raise NotImplementedError, "rename_column is not implemented" 228: 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'
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 321 321: def rename_index(table_name, old_name, new_name) 322: # this is a naive implementation; some DBs may support this more efficiently (Postgres, for instance) 323: old_index_def = indexes(table_name).detect { |i| i.name == old_name } 324: return unless old_index_def 325: remove_index(table_name, :name => old_name) 326: add_index(table_name, old_index_def.columns, :name => new_name, :unique => old_index_def.unique) 327: end
Renames a table.
Example
rename_table('octopuses', 'octopi')
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 176 176: def rename_table(table_name, new_name) 177: raise NotImplementedError, "rename_table is not implemented" 178: end
Returns a string of CREATE TABLE SQL statement(s) for recreating the entire structure of the database.
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 354 354: def structure_dump 355: end
Truncates a table alias according to the limits of the current adapter.
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 12 12: def table_alias_for(table_name) 13: table_name[0..table_alias_length-1].gsub(/\./, '_') 14: end
def tables(name = nil) end
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 18 18: def table_exists?(table_name) 19: tables.include?(table_name.to_s) 20: end
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 483 483: def options_include_default?(options) 484: options.include?(:default) && !(options[:null] == false && options[:default].nil?) 485: end
Overridden by the mysql adapter for supporting index lengths
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# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 479 479: def quoted_columns_for_index(column_names, options = {}) 480: column_names.map {|name| quote_column_name(name) } 481: end