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Class: ActiveRecord::ConnectionAdapters::AbstractAdapter

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Inherits: Object
Defined in: activerecord/lib/active_record/connection_adapters/abstract_adapter.rb,
activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb

Overview

Active Record supports multiple database systems. AbstractAdapter and related classes form the abstraction layer which makes this possible. An AbstractAdapter represents a connection to a database, and provides an abstract interface for database-specific functionality such as establishing a connection, escaping values, building the right SQL fragments for ':offset' and ':limit' options, etc.

All the concrete database adapters follow the interface laid down in this class. ActiveRecord::Base.connection returns an AbstractAdapter object, which you can use.

Most of the methods in the adapter are useful during migrations. Most notably, the instance methods provided by SchemaStatement are very useful.

Constant Summary

::ActiveSupport::Callbacks - Included

CALLBACK_FILTER_TYPES

Class Method Summary

::ActiveSupport::DescendantsTracker - self

clear, descendants, direct_descendants,
store_inherited

This is the only method that is not thread safe, but is only ever called during the eager loading phase.

Instance Attribute Summary

DatabaseStatements - Included

#begin_transaction, #commit_transaction, #current_transaction, #open_transactions, #rollback_transaction,
#supports_statement_cache?

Returns true when the connection adapter supports prepared statement caching, otherwise returns false

#transaction_open?, #within_new_transaction

Instance Method Summary

ColumnDumper - Included

#column_spec,
#migration_keys

Lists the valid migration options.

#prepare_column_options

This can be overridden on a Adapter level basis to support other extended datatypes (Example: Adding an array option in the PostgreSQLAdapter).

::ActiveSupport::Callbacks - Included

#run_callbacks

Runs the callbacks for the given event.

::ActiveRecord::QueryCache - Included

DatabaseLimits - Included

#allowed_index_name_length

Returns the maximum allowed length for an index name.

#column_name_length

Returns the maximum length of a column name.

#columns_per_multicolumn_index

Returns the maximum number of columns in a multicolumn index.

#columns_per_table

Returns the maximum number of columns per table.

#in_clause_length

Returns the maximum number of elements in an IN (x,y,z) clause.

#index_name_length

Returns the maximum length of an index name.

#indexes_per_table

Returns the maximum number of indexes per table.

#joins_per_query

Returns maximum number of joins in a single query.

#sql_query_length

Returns the maximum length of an SQL query.

#table_alias_length

Returns the maximum length of a table alias.

#table_name_length

Returns the maximum length of a table name.

Quoting - Included

#quote

Quotes the column value to help prevent SQL injection attacks.

#quote_column_name

Quotes the column name.

#quote_string

Quotes a string, escaping any ' (single quote) and \ (backslash) characters.

#quote_table_name

Quotes the table name.

#quote_table_name_for_assignment

Override to return the quoted table name for assignment.

#quoted_date, #quoted_false, #quoted_true,
#type_cast

Cast a value to a type that the database understands.

#unquoted_false, #unquoted_true

DatabaseStatements - Included

#add_transaction_record

Register a record with the current transaction so that its after_commit and after_rollback callbacks can be called.

#begin_db_transaction

Begins the transaction (and turns off auto-committing).

#begin_isolated_db_transaction

Begins the transaction with the isolation level set.

#commit_db_transaction

Commits the transaction (and turns on auto-committing).

#default_sequence_name,
#delete

Executes the delete statement and returns the number of rows affected.

#empty_insert_statement_value,
#exec_delete

Executes delete sql statement in the context of this connection using binds as the bind substitutes.

#exec_insert

Executes insert sql statement in the context of this connection using binds as the bind substitutes.

#exec_query

Executes sql statement in the context of this connection using binds as the bind substitutes.

#exec_update

Executes update sql statement in the context of this connection using binds as the bind substitutes.

#execute

Executes the SQL statement in the context of this connection.

#initialize,
#insert

Returns the last auto-generated ID from the affected table.

#insert_fixture

Inserts the given fixture into the table.

#reset_sequence!

Set the sequence to the max value of the table's column.

#rollback_db_transaction

Rolls back the transaction (and turns on auto-committing).

#rollback_to_savepoint,
#sanitize_limit

Sanitizes the given LIMIT parameter in order to prevent SQL injection.

#select_all

Returns an ::ActiveRecord::Result instance.

#select_one

Returns a record hash with the column names as keys and column values as values.

#select_rows

Returns an array of arrays containing the field values.

#select_value

Returns a single value from a record.

#select_values

Returns an array of the values of the first column in a select:

#to_sql

Converts an arel AST to SQL.

#transaction

Runs the given block in a database transaction, and returns the result of the block.

#transaction_isolation_levels, #transaction_state,
#truncate

Executes the truncate statement.

#update

Executes the update statement and returns the number of rows affected.

SchemaStatements - Included

#add_belongs_to
#add_column

Adds a new column to the named table.

#add_foreign_key

Adds a new foreign key.

#add_index

Adds a new index to the table.

#add_reference

Adds a reference.

#add_timestamps

Adds timestamps (created_at and updated_at) columns to table_name.

#assume_migrated_upto_version,
#change_column

Changes the column's definition according to the new options.

#change_column_default

Sets a new default value for a column:

#change_column_null

Sets or removes a NOT NULL constraint on a column.

#change_table

A block for changing columns in table.

#column_exists?

Checks to see if a column exists in a given table.

#columns

Returns an array of Column objects for the table specified by table_name.

#create_join_table

Creates a new join table with the name created using the lexical order of the first two arguments.

#create_table

Creates a new table with the name table_name.

#data_source_exists?

Checks to see if the data source name exists on the database.

#data_sources

Returns the relation names useable to back Active Record models.

#drop_join_table

Drops the join table specified by the given arguments.

#drop_table

Drops a table from the database.

#foreign_keys

Returns an array of foreign keys for the given table.

#index_exists?

Checks to see if an index exists on a table for a given index definition.

#index_name_exists?

Verifies the existence of an index with a given name.

#initialize_schema_migrations_table

Should not be called normally, but this operation is non-destructive.

#native_database_types

Returns a hash of mappings from the abstract data types to the native database types.

#remove_belongs_to
#remove_column

Removes the column from the table definition.

#remove_columns

Removes the given columns from the table definition.

#remove_foreign_key

Removes the given foreign key from the table.

#remove_index

Removes the given index from the table.

#remove_reference

Removes the reference(s).

#remove_timestamps

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

#rename_column

Renames a column.

#rename_index

Renames an index.

#rename_table

Renames a table.

#table_alias_for

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

#table_exists?

Checks to see if the table table_name exists on the database.

Constructor Details

This class inherits a constructor from ActiveRecord::QueryCache

Class Method Details

.type_cast_config_to_boolean(config)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 91

def self.type_cast_config_to_boolean(config)
  if config == "false"
    false
  else
    config
  end
end

.type_cast_config_to_integer(config)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 83

def self.type_cast_config_to_integer(config)
  if config =~ SIMPLE_INT
    config.to_i
  else
    config
  end
end

Instance Attribute Details

#active?Boolean (readonly)

Checks whether the connection to the database is still active. This includes checking whether the database is actually capable of responding, i.e. whether the connection isn't stale.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 296

def active?
end

#in_use? (readonly)

Alias for #owner.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 81

alias :in_use? :owner

#logger (readonly)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 80

attr_reader :schema_cache, :owner, :logger

#owner (readonly) Also known as: #in_use?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 80

attr_reader :schema_cache, :owner, :logger

#pool (rw)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 79

attr_accessor :visitor, :pool

#prepared_statements (readonly)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 99

attr_reader :prepared_statements

#requires_reloading?Boolean (readonly)

Returns true if its required to reload the connection between requests for development mode.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 332

def requires_reloading?
  false
end

#schema_cache (rw)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 80

attr_reader :schema_cache, :owner, :logger

#schema_cache=(cache) (rw)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 162

def schema_cache=(cache)
  cache.connection = self
  @schema_cache = cache
end

#supports_bulk_alter?Boolean (readonly)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 201

def supports_bulk_alter?
  false
end

#supports_ddl_transactions?Boolean (readonly)

Does this adapter support DDL rollbacks in transactions? That is, would CREATE TABLE or ALTER TABLE get rolled back by a transaction?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 197

def supports_ddl_transactions?
  false
end

#supports_explain?Boolean (readonly)

Does this adapter support explain?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 228

def supports_explain?
  false
end

#supports_extensions?Boolean (readonly)

Does this adapter support database extensions?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 238

def supports_extensions?
  false
end

#supports_foreign_keys?Boolean (readonly)

Does this adapter support creating foreign key constraints?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 249

def supports_foreign_keys?
  false
end

#supports_index_sort_order?Boolean (readonly)

Does this adapter support index sort order?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 218

def supports_index_sort_order?
  false
end

#supports_indexes_in_create?Boolean (readonly)

Does this adapter support creating indexes in the same statement as creating the table?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 244

def supports_indexes_in_create?
  false
end

#supports_migrations?Boolean (readonly)

Does this adapter support migrations?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 185

def supports_migrations?
  false
end

#supports_partial_index?Boolean (readonly)

Does this adapter support partial indices?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 223

def supports_partial_index?
  false
end

#supports_primary_key?Boolean (readonly)

Can this adapter determine the primary key for tables not attached to an Active Record class, such as join tables?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 191

def supports_primary_key?
  false
end

#supports_savepoints?Boolean (readonly)

Does this adapter support savepoints?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 206

def supports_savepoints?
  false
end

#supports_transaction_isolation?Boolean (readonly)

Does this adapter support setting the isolation level for a transaction?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 233

def supports_transaction_isolation?
  false
end

#supports_views?Boolean (readonly)

Does this adapter support views?

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 254

def supports_views?
  false
end

#visitor (rw)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 79

attr_accessor :visitor, :pool

Instance Method Details

#adapter_name

Returns the human-readable name of the adapter. Use mixed case - one can always use downcase if needed.

[ GitHub ]

  
# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 180

def adapter_name
  self.class::ADAPTER_NAME
end

#case_insensitive_comparison(table, attribute, column, value)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 369

def case_insensitive_comparison(table, attribute, column, value)
  table[attribute].lower.eq(table.lower(value))
end

#case_sensitive_comparison(table, attribute, column, value)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 363

def case_sensitive_comparison(table, attribute, column, value)
  table_attr = table[attribute]
  value = case_sensitive_modifier(value, table_attr) unless value.nil?
  table_attr.eq(value)
end

#case_sensitive_modifier(node, table_attribute)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 359

def case_sensitive_modifier(node, table_attribute)
  node
end

#clear_cache!

Clear any caching the database adapter may be doing, for example clearing the prepared statement cache. This is database specific.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 327

def clear_cache!
  # this should be overridden by concrete adapters
end

#close

Check the connection back in to the connection pool

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 378

def close
  pool.checkin self
end

#collector

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 138

def collector
  if prepared_statements
    SQLString.new
  else
    BindCollector.new
  end
end

#create_savepoint(name = nil)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 353

def create_savepoint(name = nil)
end

#current_savepoint_name

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 373

def current_savepoint_name
  current_transaction.savepoint_name
end

#disable_extension(name)

This is meant to be implemented by the adapters that support extensions

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 259

def disable_extension(name)
end

#disable_referential_integrity

Override to turn off referential integrity while executing &block.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 287

def disable_referential_integrity
  yield
end

#disconnect!

Disconnects from the database if already connected. Otherwise, this method does nothing.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 309

def disconnect!
  clear_cache!
  reset_transaction
end

#enable_extension(name)

This is meant to be implemented by the adapters that support extensions

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 263

def enable_extension(name)
end

#expire

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 167

def expire
  @owner = nil
end

#extensions

A list of extensions, to be filled in by adapters that support them.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 267

def extensions
  []
end

#index_algorithms

A list of index algorithms, to be filled by adapters that support them.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 272

def index_algorithms
  {}
end

#lease

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 154

def lease
  synchronize do
    unless in_use?
      @owner = Thread.current
    end
  end
end

#new_column(name, default, cast_type, sql_type = nil, null = true)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 388

def new_column(name, default, cast_type, sql_type = nil, null = true)
  Column.new(name, default, cast_type, sql_type, null)
end

#prefetch_primary_key?(table_name = nil) ⇒ Boolean

Should primary key values be selected from their corresponding sequence before the insert statement? If true, next_sequence_value is called before each insert to set the record's primary key.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 213

def prefetch_primary_key?(table_name = nil)
  false
end

#raw_connection

Provides access to the underlying database driver for this adapter. For example, this method returns a ::Mysql object in case of MysqlAdapter, and a PGconn object in case of PostgreSQLAdapter.

This is useful for when you need to call a proprietary method such as PostgreSQL's lo_* methods.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 349

def raw_connection
  @connection
end

#reconnect!

Disconnects from the database if already connected, and establishes a new connection with the database. Implementors should call super if they override the default implementation.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 302

def reconnect!
  clear_cache!
  reset_transaction
end

#release_savepoint(name = nil)

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 356

def release_savepoint(name = nil)
end

#reset!

Reset the state of this connection, directing the DBMS to clear transactions and other connection-related server-side state. Usually a database-dependent operation.

The default implementation does nothing; the implementation should be overridden by concrete adapters.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 320

def reset!
  # this should be overridden by concrete adapters
end

#schema_creation

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 150

def schema_creation
  SchemaCreation.new self
end

#substitute_at(column, _unused = 0)

Returns a bind substitution value given a bind column NOTE: The column param is currently being used by the sqlserver-adapter

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 280

def substitute_at(column, _unused = 0)
  Arel::Nodes::BindParam.new
end

#unprepared_statement

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 171

def unprepared_statement
  old_prepared_statements, @prepared_statements = @prepared_statements, false
  yield
ensure
  @prepared_statements = old_prepared_statements
end

#valid_type?(type) ⇒ Boolean

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 146

def valid_type?(type)
  true
end

#verify!(*ignored)

Checks whether the connection to the database is still active (i.e. not stale). This is done under the hood by calling #active?. If the connection is no longer active, then this method will reconnect to the database.

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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 339

def verify!(*ignored)
  reconnect! unless active?
end