Class: ActiveRecord::ConnectionAdapters::AbstractAdapter
- Inherits:
-
Object
- Object
- ActiveRecord::ConnectionAdapters::AbstractAdapter
- Includes:
- DatabaseLimits, DatabaseStatements, QueryCache, Quoting, SchemaStatements, ActiveSupport::Callbacks
- Defined in:
- lib/active_record/connection_adapters/abstract_adapter.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.
Direct Known Subclasses
Mysql2Adapter, MysqlAdapter, PostgreSQLAdapter, SQLiteAdapter
Instance Attribute Summary collapse
-
#logger ⇒ Object
readonly
Returns the value of attribute logger.
-
#visitor ⇒ Object
Returns the value of attribute visitor.
Attributes included from QueryCache
#query_cache, #query_cache_enabled
Class Method Summary collapse
-
.visitor_for(pool) ⇒ Object
Returns a visitor instance for this adaptor, which conforms to the Arel::ToSql interface.
Instance Method Summary collapse
-
#active? ⇒ Boolean
Checks whether the connection to the database is still active.
-
#adapter_name ⇒ Object
Returns the human-readable name of the adapter.
- #case_sensitive_modifier(node) ⇒ Object
-
#clear_cache! ⇒ Object
Clear any caching the database adapter may be doing, for example clearing the prepared statement cache.
- #create_savepoint ⇒ Object
- #current_savepoint_name ⇒ Object
- #decrement_open_transactions ⇒ Object
-
#disable_referential_integrity ⇒ Object
Override to turn off referential integrity while executing
&block
. -
#disconnect! ⇒ Object
Disconnects from the database if already connected.
- #increment_open_transactions ⇒ Object
-
#initialize(connection, logger = nil) ⇒ AbstractAdapter
constructor
:nodoc:.
- #open_transactions ⇒ Object
-
#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.
-
#quote_table_name(name) ⇒ Object
Override to return the quoted table name.
-
#raw_connection ⇒ Object
Provides access to the underlying database driver for this adapter.
-
#reconnect! ⇒ Object
Disconnects from the database if already connected, and establishes a new connection with the database.
- #release_savepoint ⇒ Object
-
#requires_reloading? ⇒ Boolean
Returns true if its required to reload the connection between requests for development mode.
-
#reset! ⇒ Object
Reset the state of this connection, directing the DBMS to clear transactions and other connection-related server-side state.
- #rollback_to_savepoint ⇒ Object
-
#substitute_at(column, index) ⇒ Object
Returns a bind substitution value given a
column
and list of currentbinds
. - #supports_bulk_alter? ⇒ Boolean
-
#supports_count_distinct? ⇒ Boolean
Does this adapter support using DISTINCT within COUNT? This is
true
for all adapters except sqlite. -
#supports_ddl_transactions? ⇒ Boolean
Does this adapter support DDL rollbacks in transactions? That is, would CREATE TABLE or ALTER TABLE get rolled back by a transaction? PostgreSQL, SQL Server, and others support this.
-
#supports_migrations? ⇒ Boolean
Does this adapter support migrations? Backend specific, as the abstract adapter always returns
false
. -
#supports_primary_key? ⇒ Boolean
Can this adapter determine the primary key for tables not attached to an Active Record class, such as join tables? Backend specific, as the abstract adapter always returns
false
. -
#supports_savepoints? ⇒ Boolean
Does this adapter support savepoints? PostgreSQL and MySQL do, SQLite < 3.6.8 does not.
- #transaction_joinable=(joinable) ⇒ Object
-
#verify!(*ignored) ⇒ Object
Checks whether the connection to the database is still active (i.e. not stale).
Methods included from QueryCache
#cache, #clear_query_cache, dirties_query_cache, #disable_query_cache!, #enable_query_cache!, included, #select_all, #uncached
Methods included from DatabaseLimits
#column_name_length, #columns_per_multicolumn_index, #columns_per_table, #in_clause_length, #index_name_length, #indexes_per_table, #joins_per_query, #sql_query_length, #table_alias_length, #table_name_length
Methods included from Quoting
#quote, #quote_column_name, #quote_string, #quoted_date, #quoted_false, #quoted_true, #type_cast
Methods included from DatabaseStatements
#add_limit_offset!, #add_transaction_record, #begin_db_transaction, #case_sensitive_equality_operator, #commit_db_transaction, #default_sequence_name, #delete, #empty_insert_statement_value, #exec_delete, #exec_insert, #exec_query, #exec_update, #execute, #insert, #insert_fixture, #join_to_update, #limited_update_conditions, #outside_transaction?, #reset_sequence!, #rollback_db_transaction, #sanitize_limit, #select_all, #select_one, #select_rows, #select_value, #select_values, #supports_statement_cache?, #to_sql, #transaction, #update
Methods included from SchemaStatements
#add_column, #add_column_options!, #add_index, #add_timestamps, #assume_migrated_upto_version, #change_column, #change_column_default, #change_table, #column_exists?, #columns, #create_table, #distinct, #drop_table, #dump_schema_information, #index_exists?, #index_name, #index_name_exists?, #initialize_schema_migrations_table, #native_database_types, #remove_column, #remove_index, #remove_index!, #remove_timestamps, #rename_column, #rename_index, #rename_table, #structure_dump, #table_alias_for, #table_exists?, #type_to_sql
Constructor Details
#initialize(connection, logger = nil) ⇒ AbstractAdapter
:nodoc:
45 46 47 48 49 50 51 52 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 45 def initialize(connection, logger = nil) #:nodoc: @active = nil @connection, @logger = connection, logger @query_cache_enabled = false @query_cache = Hash.new { |h,sql| h[sql] = {} } @instrumenter = ActiveSupport::Notifications.instrumenter @visitor = nil end |
Instance Attribute Details
#logger ⇒ Object (readonly)
Returns the value of attribute logger.
43 44 45 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 43 def logger @logger end |
#visitor ⇒ Object
Returns the value of attribute visitor.
42 43 44 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 42 def visitor @visitor end |
Class Method Details
.visitor_for(pool) ⇒ Object
Returns a visitor instance for this adaptor, which conforms to the Arel::ToSql interface
55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 55 def self.visitor_for(pool) # :nodoc: adapter = pool.spec.config[:adapter] if Arel::Visitors::VISITORS[adapter] ActiveSupport::Deprecation.warn( "Arel::Visitors::VISITORS is deprecated and will be removed. Database adapters " \ "should define a visitor_for method which returns the appropriate visitor for " \ "the database. For example, MysqlAdapter.visitor_for(pool) returns " \ "Arel::Visitors::MySQL.new(pool)." ) Arel::Visitors::VISITORS[adapter].new(pool) else Arel::Visitors::ToSql.new(pool) end end |
Instance Method Details
#active? ⇒ Boolean
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.
147 148 149 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 147 def active? @active != false end |
#adapter_name ⇒ Object
Returns the human-readable name of the adapter. Use mixed case - one can always use downcase if needed.
74 75 76 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 74 def adapter_name 'Abstract' end |
#case_sensitive_modifier(node) ⇒ Object
229 230 231 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 229 def case_sensitive_modifier(node) node end |
#clear_cache! ⇒ Object
Clear any caching the database adapter may be doing, for example clearing the prepared statement cache. This is database specific.
176 177 178 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 176 def clear_cache! # this should be overridden by concrete adapters end |
#create_savepoint ⇒ Object
220 221 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 220 def create_savepoint end |
#current_savepoint_name ⇒ Object
233 234 235 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 233 def current_savepoint_name "active_record_#{open_transactions}" end |
#decrement_open_transactions ⇒ Object
212 213 214 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 212 def decrement_open_transactions @open_transactions -= 1 end |
#disable_referential_integrity ⇒ Object
Override to turn off referential integrity while executing &block
.
138 139 140 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 138 def disable_referential_integrity yield end |
#disconnect! ⇒ Object
Disconnects from the database if already connected. Otherwise, this method does nothing.
159 160 161 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 159 def disconnect! @active = false end |
#increment_open_transactions ⇒ Object
207 208 209 210 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 207 def increment_open_transactions @open_transactions ||= 0 @open_transactions += 1 end |
#open_transactions ⇒ Object
203 204 205 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 203 def open_transactions @open_transactions ||= 0 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. This is false for all adapters but Firebird.
118 119 120 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 118 def prefetch_primary_key?(table_name = nil) false end |
#quote_table_name(name) ⇒ Object
Override to return the quoted table name. Defaults to column quoting.
125 126 127 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 125 def quote_table_name(name) quote_column_name(name) end |
#raw_connection ⇒ Object
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.
199 200 201 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 199 def raw_connection @connection end |
#reconnect! ⇒ Object
Disconnects from the database if already connected, and establishes a new connection with the database.
153 154 155 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 153 def reconnect! @active = true end |
#release_savepoint ⇒ Object
226 227 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 226 def release_savepoint end |
#requires_reloading? ⇒ Boolean
Returns true if its required to reload the connection between requests for development mode. This is not the case for Ruby/MySQL and it’s not necessary for any adapters except SQLite.
182 183 184 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 182 def requires_reloading? false end |
#reset! ⇒ Object
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.
169 170 171 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 169 def reset! # this should be overridden by concrete adapters end |
#rollback_to_savepoint ⇒ Object
223 224 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 223 def rollback_to_savepoint end |
#substitute_at(column, index) ⇒ Object
Returns a bind substitution value given a column
and list of current binds
131 132 133 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 131 def substitute_at(column, index) Arel::Nodes::BindParam.new '?' end |
#supports_bulk_alter? ⇒ Boolean
104 105 106 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 104 def supports_bulk_alter? false end |
#supports_count_distinct? ⇒ Boolean
Does this adapter support using DISTINCT within COUNT? This is true
for all adapters except sqlite.
93 94 95 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 93 def supports_count_distinct? true end |
#supports_ddl_transactions? ⇒ Boolean
Does this adapter support DDL rollbacks in transactions? That is, would CREATE TABLE or ALTER TABLE get rolled back by a transaction? PostgreSQL, SQL Server, and others support this. MySQL and others do not.
100 101 102 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 100 def supports_ddl_transactions? false end |
#supports_migrations? ⇒ Boolean
Does this adapter support migrations? Backend specific, as the abstract adapter always returns false
.
80 81 82 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 80 def supports_migrations? false end |
#supports_primary_key? ⇒ Boolean
Can this adapter determine the primary key for tables not attached to an Active Record class, such as join tables? Backend specific, as the abstract adapter always returns false
.
87 88 89 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 87 def supports_primary_key? false end |
#supports_savepoints? ⇒ Boolean
Does this adapter support savepoints? PostgreSQL and MySQL do, SQLite < 3.6.8 does not.
110 111 112 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 110 def supports_savepoints? false end |
#transaction_joinable=(joinable) ⇒ Object
216 217 218 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 216 def transaction_joinable=(joinable) @transaction_joinable = joinable end |
#verify!(*ignored) ⇒ Object
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.
189 190 191 |
# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 189 def verify!(*ignored) reconnect! unless active? end |