Class Sequel::Database
In: lib/sequel/adapters/do.rb
lib/sequel/adapters/jdbc.rb
lib/sequel/adapters/mysql.rb
lib/sequel/adapters/postgres.rb
lib/sequel/adapters/sqlite.rb
lib/sequel/adapters/swift.rb
lib/sequel/database.rb
lib/sequel/database/schema_methods.rb
lib/sequel/database/connecting.rb
lib/sequel/database/dataset.rb
lib/sequel/database/dataset_defaults.rb
lib/sequel/database/logging.rb
lib/sequel/database/misc.rb
lib/sequel/database/query.rb
lib/sequel/extensions/query.rb
lib/sequel/extensions/schema_dumper.rb
Parent: Sequel::Database

A Database object represents a virtual connection to a database. The Database class is meant to be subclassed by database adapters in order to provide the functionality needed for executing queries.

Methods

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Included Modules

Constants

DISCONNECT_ERROR_RE = /terminating connection due to administrator command/
MYSQL_DATABASE_DISCONNECT_ERRORS = /\A(Commands out of sync; you can't run this command now|Can't connect to local MySQL server through socket|MySQL server has gone away|Lost connection to MySQL server during query)/   Mysql::Error messages that indicate the current connection should be disconnected

Attributes

conversion_procs  [R]  A hash of conversion procs, keyed by type integer (oid) and having callable values for the conversion proc for that type.
conversion_procs  [R]  The conversion procs to use for this database
conversion_procs  [R]  Hash of conversion procs for the current database
convert_invalid_date_time  [R]  By default, Sequel raises an exception if in invalid date or time is used. However, if this is set to nil or :nil, the adapter treats dates like 0000-00-00 and times like 838:00:00 as nil values. If set to :string, it returns the strings as is.
convert_tinyint_to_bool  [R]  Whether to convert tinyint columns to bool for the current database
convert_types  [RW]  Whether to convert some Java types to ruby types when retrieving rows. True by default, can be set to false to roughly double performance when fetching rows.
database_type  [R]  The type of database we are connecting to
driver  [R]  The Java database driver we are using
swift_class  [RW]  The Swift adapter class being used by this database. Connections in this database‘s connection pool will be instances of this class.

Public Class methods

[Source]

    # File lib/sequel/adapters/mysql.rb, line 61
61:       def initialize(opts={})
62:         super
63:         @conversion_procs = MYSQL_TYPES.dup
64:         self.convert_tinyint_to_bool = Sequel::MySQL.convert_tinyint_to_bool
65:         self.convert_invalid_date_time = Sequel::MySQL.convert_invalid_date_time
66:       end

Add the primary_keys and primary_key_sequences instance variables, so we can get the correct return values for inserted rows.

[Source]

     # File lib/sequel/adapters/postgres.rb, line 210
210:       def initialize(*args)
211:         super
212:         @primary_keys = {}
213:         @primary_key_sequences = {}
214:       end

[Source]

    # File lib/sequel/adapters/sqlite.rb, line 53
53:       def initialize(opts={})
54:         super
55:         @conversion_procs = SQLITE_TYPES.dup
56:         @conversion_procs['timestamp'] = method(:to_application_timestamp)
57:         @conversion_procs['datetime'] = method(:to_application_timestamp)
58:       end

Call the DATABASE_SETUP proc directly after initialization, so the object always uses sub adapter specific code. Also, raise an error immediately if the connection doesn‘t have a db_type specified, since one is required to include the correct subadapter.

[Source]

    # File lib/sequel/adapters/swift.rb, line 47
47:       def initialize(opts)
48:         super
49:         if db_type = opts[:db_type] and !db_type.to_s.empty? 
50:           if prok = DATABASE_SETUP[db_type.to_s.to_sym]
51:             prok.call(self)
52:           else
53:             raise(Error, "No :db_type option specified")
54:           end
55:         else
56:           raise(Error, ":db_type option not valid, should be postgres, mysql, or sqlite")
57:         end
58:       end

Call the DATABASE_SETUP proc directly after initialization, so the object always uses sub adapter specific code. Also, raise an error immediately if the connection doesn‘t have a uri, since JDBC requires one.

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 151
151:       def initialize(opts)
152:         super
153:         @convert_types = typecast_value_boolean(@opts.fetch(:convert_types, true))
154:         raise(Error, "No connection string specified") unless uri
155:         
156:         resolved_uri = jndi? ? get_uri_from_jndi : uri
157: 
158:         if match = /\Ajdbc:([^:]+)/.match(resolved_uri) and prok = DATABASE_SETUP[match[1].to_sym]
159:           @driver = prok.call(self)
160:         end        
161:       end

Call the DATABASE_SETUP proc directly after initialization, so the object always uses sub adapter specific code. Also, raise an error immediately if the connection doesn‘t have a uri, since DataObjects requires one.

[Source]

    # File lib/sequel/adapters/do.rb, line 50
50:       def initialize(opts)
51:         super
52:         raise(Error, "No connection string specified") unless uri
53:         if prok = DATABASE_SETUP[subadapter.to_sym]
54:           prok.call(self)
55:         end
56:       end

Public Instance methods

Execute the given stored procedure with the give name. If a block is given, the stored procedure should return rows.

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 165
165:       def call_sproc(name, opts = {})
166:         args = opts[:args] || []
167:         sql = "{call #{name}(#{args.map{'?'}.join(',')})}"
168:         synchronize(opts[:server]) do |conn|
169:           cps = conn.prepareCall(sql)
170: 
171:           i = 0
172:           args.each{|arg| set_ps_arg(cps, arg, i+=1)}
173: 
174:           begin
175:             if block_given?
176:               yield log_yield(sql){cps.executeQuery}
177:             else
178:               case opts[:type]
179:               when :insert
180:                 log_yield(sql){cps.executeUpdate}
181:                 last_insert_id(conn, opts)
182:               else
183:                 log_yield(sql){cps.executeUpdate}
184:               end
185:             end
186:           rescue NativeException, JavaSQL::SQLException => e
187:             raise_error(e)
188:           ensure
189:             cps.close
190:           end
191:         end
192:       end

Connect to the database using JavaSQL::DriverManager.getConnection.

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 195
195:       def connect(server)
196:         opts = server_opts(server)
197:         conn = if jndi?
198:           get_connection_from_jndi
199:         else
200:           args = [uri(opts)]
201:           args.concat([opts[:user], opts[:password]]) if opts[:user] && opts[:password]
202:           begin
203:             JavaSQL::DriverManager.setLoginTimeout(opts[:login_timeout]) if opts[:login_timeout]
204:             JavaSQL::DriverManager.getConnection(*args)
205:           rescue => e
206:             raise e unless driver
207:             # If the DriverManager can't get the connection - use the connect
208:             # method of the driver. (This happens under Tomcat for instance)
209:             props = java.util.Properties.new
210:             if opts && opts[:user] && opts[:password]
211:               props.setProperty("user", opts[:user])
212:               props.setProperty("password", opts[:password])
213:             end
214:             opts[:jdbc_properties].each{|k,v| props.setProperty(k.to_s, v)} if opts[:jdbc_properties]
215:             begin
216:               driver.new.connect(args[0], props)
217:             rescue => e2
218:               e.message << "\n#{e2.class.name}: #{e2.message}"
219:               raise e
220:             end
221:           end
222:         end
223:         setup_connection(conn)
224:       end

Connects to the database. In addition to the standard database options, using the :encoding or :charset option changes the client encoding for the connection.

[Source]

     # File lib/sequel/adapters/postgres.rb, line 219
219:       def connect(server)
220:         opts = server_opts(server)
221:         conn = if SEQUEL_POSTGRES_USES_PG
222:           connection_params = {
223:             :host => opts[:host],
224:             :port => opts[:port] || 5432,
225:             :tty => '',
226:             :dbname => opts[:database],
227:             :user => opts[:user],
228:             :password => opts[:password],
229:             :connect_timeout => opts[:connect_timeout] || 20
230:           }.delete_if { |key, value| blank_object?(value) }
231:           Adapter.connect(connection_params)
232:         else
233:           Adapter.connect(
234:             (opts[:host] unless blank_object?(opts[:host])),
235:             opts[:port] || 5432,
236:             nil, '',
237:             opts[:database],
238:             opts[:user],
239:             opts[:password]
240:           )
241:         end
242:         if encoding = opts[:encoding] || opts[:charset]
243:           if conn.respond_to?(:set_client_encoding)
244:             conn.set_client_encoding(encoding)
245:           else
246:             conn.async_exec("set client_encoding to '#{encoding}'")
247:           end
248:         end
249:         conn.db = self
250:         conn.apply_connection_settings
251:         @conversion_procs ||= get_conversion_procs(conn)
252:         conn
253:       end

Connect to the database. Since SQLite is a file based database, the only options available are :database (to specify the database name), and :timeout, to specify how long to wait for the database to be available if it is locked, given in milliseconds (default is 5000).

[Source]

    # File lib/sequel/adapters/sqlite.rb, line 64
64:       def connect(server)
65:         opts = server_opts(server)
66:         opts[:database] = ':memory:' if blank_object?(opts[:database])
67:         db = ::SQLite3::Database.new(opts[:database])
68:         db.busy_timeout(opts.fetch(:timeout, 5000))
69:         
70:         connection_pragmas.each{|s| log_yield(s){db.execute_batch(s)}}
71:         
72:         class << db
73:           attr_reader :prepared_statements
74:         end
75:         db.instance_variable_set(:@prepared_statements, {})
76:         
77:         db
78:       end

Setup a DataObjects::Connection to the database.

[Source]

    # File lib/sequel/adapters/do.rb, line 59
59:       def connect(server)
60:         setup_connection(::DataObjects::Connection.new(uri(server_opts(server))))
61:       end

Create an instance of swift_class for the given options.

[Source]

    # File lib/sequel/adapters/swift.rb, line 61
61:       def connect(server)
62:         setup_connection(swift_class.new(server_opts(server)))
63:       end

Connect to the database. In addition to the usual database options, the following options have effect:

  • :auto_is_null - Set to true to use MySQL default behavior of having a filter for an autoincrement column equals NULL to return the last inserted row.
  • :charset - Same as :encoding (:encoding takes precendence)
  • :compress - Set to false to not compress results from the server
  • :config_default_group - The default group to read from the in the MySQL config file.
  • :config_local_infile - If provided, sets the Mysql::OPT_LOCAL_INFILE option on the connection with the given value.
  • :connect_timeout - Set the timeout in seconds before a connection attempt is abandoned.
  • :encoding - Set all the related character sets for this connection (connection, client, database, server, and results).
  • :read_timeout - Set the timeout in seconds for reading back results to a query.
  • :socket - Use a unix socket file instead of connecting via TCP/IP.
  • :timeout - Set the timeout in seconds before the server will disconnect this connection (a.k.a @@wait_timeout).

[Source]

     # File lib/sequel/adapters/mysql.rb, line 89
 89:       def connect(server)
 90:         opts = server_opts(server)
 91:         conn = Mysql.init
 92:         conn.options(Mysql::READ_DEFAULT_GROUP, opts[:config_default_group] || "client")
 93:         conn.options(Mysql::OPT_LOCAL_INFILE, opts[:config_local_infile]) if opts.has_key?(:config_local_infile)
 94:         conn.ssl_set(opts[:sslkey], opts[:sslcert], opts[:sslca], opts[:sslcapath], opts[:sslcipher]) if opts[:sslca] || opts[:sslkey]
 95:         if encoding = opts[:encoding] || opts[:charset]
 96:           # Set encoding before connecting so that the mysql driver knows what
 97:           # encoding we want to use, but this can be overridden by READ_DEFAULT_GROUP.
 98:           conn.options(Mysql::SET_CHARSET_NAME, encoding)
 99:         end
100:         if read_timeout = opts[:read_timeout] and defined? Mysql::OPT_READ_TIMEOUT
101:           conn.options(Mysql::OPT_READ_TIMEOUT, read_timeout)
102:         end
103:         if connect_timeout = opts[:connect_timeout] and defined? Mysql::OPT_CONNECT_TIMEOUT
104:           conn.options(Mysql::OPT_CONNECT_TIMEOUT, connect_timeout)
105:         end
106:         conn.real_connect(
107:           opts[:host] || 'localhost',
108:           opts[:user],
109:           opts[:password],
110:           opts[:database],
111:           (opts[:port].to_i if opts[:port]),
112:           opts[:socket],
113:           Mysql::CLIENT_MULTI_RESULTS +
114:           Mysql::CLIENT_MULTI_STATEMENTS +
115:           (opts[:compress] == false ? 0 : Mysql::CLIENT_COMPRESS)
116:         )
117:         sqls = []
118:         # Set encoding a slightly different way after connecting,
119:         # in case the READ_DEFAULT_GROUP overrode the provided encoding.
120:         # Doesn't work across implicit reconnects, but Sequel doesn't turn on
121:         # that feature.
122:         sqls << "SET NAMES #{literal(encoding.to_s)}" if encoding
123: 
124:         # Increase timeout so mysql server doesn't disconnect us
125:         # Value used by default is maximum allowed value on Windows.
126:         sqls << "SET @@wait_timeout = #{opts[:timeout] || 2147483}"
127: 
128:         # By default, MySQL 'where id is null' selects the last inserted id
129:         sqls << "SET SQL_AUTO_IS_NULL=0" unless opts[:auto_is_null]
130: 
131:         sqls.each{|sql| log_yield(sql){conn.query(sql)}}
132: 
133:         add_prepared_statements_cache(conn)
134:         conn
135:       end

Modify the type translators for the date, time, and timestamp types depending on the value given.

[Source]

     # File lib/sequel/adapters/mysql.rb, line 139
139:       def convert_invalid_date_time=(v)
140:         m0 = ::Sequel.method(:string_to_time)
141:         @conversion_procs[11] = (v != false) ?  lambda{|v| convert_date_time(v, &m0)} : m0
142:         m1 = ::Sequel.method(:string_to_date) 
143:         m = (v != false) ? lambda{|v| convert_date_time(v, &m1)} : m1
144:         [10, 14].each{|i| @conversion_procs[i] = m}
145:         m2 = method(:to_application_timestamp)
146:         m = (v != false) ? lambda{|v| convert_date_time(v, &m2)} : m2
147:         [7, 12].each{|i| @conversion_procs[i] = m}
148:         @convert_invalid_date_time = v
149:       end

Modify the type translator used for the tinyint type based on the value given.

[Source]

     # File lib/sequel/adapters/mysql.rb, line 153
153:       def convert_tinyint_to_bool=(v)
154:         @conversion_procs[1] = TYPE_TRANSLATOR.method(v ? :boolean : :integer)
155:         @convert_tinyint_to_bool = v
156:       end

copy_table uses PostgreSQL‘s COPY SQL statement to return formatted results directly to the caller. This method is only supported if pg is the underlying ruby driver. This method should only be called if you want results returned to the client. If you are using +COPY FROM+ or +COPY TO+ with a filename, you should just use run instead of this method. This method does not currently support +COPY FROM STDIN+, but that may be supported in the future.

The table argument supports the following types:

String :Uses the first argument directly as literal SQL. If you are using a version of PostgreSQL before 9.0, you will probably want to use a string if you are using any options at all, as the syntax Sequel uses for options is only compatible with PostgreSQL 9.0+.
Dataset :Uses a query instead of a table name when copying.
other :Uses a table name (usually a symbol) when copying.

The following options are respected:

:format :The format to use. text is the default, so this should be :csv or :binary.
:options :An options SQL string to use, which should contain comma separated options.
:server :The server on which to run the query.

If a block is provided, the method continually yields to the block, one yield per row. If a block is not provided, a single string is returned with all of the data.

[Source]

     # File lib/sequel/adapters/postgres.rb, line 302
302:         def copy_table(table, opts={})
303:           sql = if table.is_a?(String)
304:             sql = table
305:           else
306:             if opts[:options] || opts[:format]
307:               options = " ("
308:               options << "FORMAT #{opts[:format]}" if opts[:format]
309:               options << "#{', ' if opts[:format]}#{opts[:options]}" if opts[:options]
310:               options << ')'
311:             end
312:             table = if table.is_a?(::Sequel::Dataset)
313:               "(#{table.sql})"
314:             else
315:               literal(table)
316:             end
317:            sql = "COPY #{table} TO STDOUT#{options}"
318:           end
319:           synchronize(opts[:server]) do |conn| 
320:             conn.execute(sql)
321:             begin
322:               if block_given?
323:                 while buf = conn.get_copy_data
324:                   yield buf
325:                 end
326:                 nil
327:               else
328:                 b = ''
329:                 b << buf while buf = conn.get_copy_data
330:                 b
331:               end
332:             ensure
333:               raise DatabaseDisconnectError, "disconnecting as a partial COPY may leave the connection in an unusable state" if buf
334:             end
335:           end 
336:         end

Execute the given SQL with the given args on an available connection.

[Source]

     # File lib/sequel/adapters/postgres.rb, line 256
256:       def execute(sql, opts={}, &block)
257:         check_database_errors do
258:           return execute_prepared_statement(sql, opts, &block) if Symbol === sql
259:           synchronize(opts[:server]){|conn| conn.execute(sql, opts[:arguments], &block)}
260:         end
261:       end

Execute the given SQL, yielding a Swift::Result if a block is given.

[Source]

    # File lib/sequel/adapters/swift.rb, line 66
66:       def execute(sql, opts={})
67:         synchronize(opts[:server]) do |conn|
68:           begin
69:             res = log_yield(sql){conn.execute(sql)}
70:             yield res if block_given?
71:             nil
72:           rescue SwiftError => e
73:             raise_error(e)
74:           end
75:         end
76:       end

Run the given SQL with the given arguments and yield each row.

[Source]

    # File lib/sequel/adapters/sqlite.rb, line 81
81:       def execute(sql, opts={}, &block)
82:         _execute(:select, sql, opts, &block)
83:       end

Execute the given SQL. If a block is given, the DataObjects::Reader created is yielded to it. A block should not be provided unless a a SELECT statement is being used (or something else that returns rows). Otherwise, the return value is the insert id if opts[:type] is :insert, or the number of affected rows, otherwise.

[Source]

    # File lib/sequel/adapters/do.rb, line 68
68:       def execute(sql, opts={})
69:         synchronize(opts[:server]) do |conn|
70:           begin
71:             command = conn.create_command(sql)
72:             res = log_yield(sql){block_given? ? command.execute_reader : command.execute_non_query}
73:           rescue ::DataObjects::Error => e
74:             raise_error(e)
75:           end
76:           if block_given?
77:             begin
78:               yield(res)
79:             ensure
80:              res.close if res
81:             end
82:           elsif opts[:type] == :insert
83:             res.insert_id
84:           else
85:             res.affected_rows
86:           end
87:         end
88:       end

Execute the given SQL. If a block is given, if should be a SELECT statement or something else that returns rows.

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 228
228:       def execute(sql, opts={}, &block)
229:         return call_sproc(sql, opts, &block) if opts[:sproc]
230:         return execute_prepared_statement(sql, opts, &block) if [Symbol, Dataset].any?{|c| sql.is_a?(c)}
231:         synchronize(opts[:server]) do |conn|
232:           statement(conn) do |stmt|
233:             if block
234:               yield log_yield(sql){stmt.executeQuery(sql)}
235:             else
236:               case opts[:type]
237:               when :ddl
238:                 log_yield(sql){stmt.execute(sql)}
239:               when :insert
240:                 log_yield(sql) do
241:                   if requires_return_generated_keys?
242:                     stmt.executeUpdate(sql, JavaSQL::Statement.RETURN_GENERATED_KEYS)
243:                   else
244:                     stmt.executeUpdate(sql)
245:                   end
246:                 end
247:                 last_insert_id(conn, opts.merge(:stmt=>stmt))
248:               else
249:                 log_yield(sql){stmt.executeUpdate(sql)}
250:               end
251:             end
252:           end
253:         end
254:       end

Drop any prepared statements on the connection when executing DDL. This is because prepared statements lock the table in such a way that you can‘t drop or alter the table while a prepared statement that references it still exists.

[Source]

    # File lib/sequel/adapters/sqlite.rb, line 93
93:       def execute_ddl(sql, opts={})
94:         synchronize(opts[:server]) do |conn|
95:           conn.prepared_statements.values.each{|cps, s| cps.close}
96:           conn.prepared_statements.clear
97:           super
98:         end
99:       end

Execute the given DDL SQL, which should not return any values or rows.

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 259
259:       def execute_ddl(sql, opts={})
260:         execute(sql, {:type=>:ddl}.merge(opts))
261:       end

Run the given SQL with the given arguments and return the number of changed rows.

[Source]

    # File lib/sequel/adapters/sqlite.rb, line 86
86:       def execute_dui(sql, opts={})
87:         _execute(:update, sql, opts)
88:       end
execute_dui(sql, opts={})

Alias for execute

Execute the SQL on the this database, returning the number of affected rows.

[Source]

    # File lib/sequel/adapters/swift.rb, line 80
80:       def execute_dui(sql, opts={})
81:         synchronize(opts[:server]) do |conn|
82:           begin
83:             log_yield(sql){conn.execute(sql).rows}
84:           rescue SwiftError => e
85:             raise_error(e)
86:           end
87:         end
88:       end

Execute the SQL on the this database, returning the number of affected rows.

[Source]

    # File lib/sequel/adapters/do.rb, line 92
92:       def execute_dui(sql, opts={})
93:         execute(sql, opts)
94:       end

Execute the SQL on this database, returning the primary key of the table being inserted to.

[Source]

     # File lib/sequel/adapters/swift.rb, line 92
 92:       def execute_insert(sql, opts={})
 93:         synchronize(opts[:server]) do |conn|
 94:           begin
 95:             log_yield(sql){conn.execute(sql).insert_id}
 96:           rescue SwiftError => e
 97:             raise_error(e)
 98:           end
 99:         end
100:       end

Execute the given INSERT SQL, returning the last inserted row id.

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 265
265:       def execute_insert(sql, opts={})
266:         execute(sql, {:type=>:insert}.merge(opts))
267:       end

Insert the values into the table and return the primary key (if automatically generated).

[Source]

     # File lib/sequel/adapters/postgres.rb, line 265
265:       def execute_insert(sql, opts={})
266:         return execute(sql, opts) if Symbol === sql
267:         check_database_errors do
268:           synchronize(opts[:server]) do |conn|
269:             conn.execute(sql, opts[:arguments])
270:             insert_result(conn, opts[:table], opts[:values])
271:           end
272:         end
273:       end

Execute the SQL on this database, returning the primary key of the table being inserted to.

[Source]

     # File lib/sequel/adapters/do.rb, line 98
 98:       def execute_insert(sql, opts={})
 99:         execute(sql, opts.merge(:type=>:insert))
100:       end

Run the given SQL with the given arguments and return the last inserted row id.

[Source]

     # File lib/sequel/adapters/sqlite.rb, line 102
102:       def execute_insert(sql, opts={})
103:         _execute(:insert, sql, opts)
104:       end

Use the JDBC metadata to get the index information for the table.

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 270
270:       def indexes(table, opts={})
271:         m = output_identifier_meth
272:         im = input_identifier_meth
273:         schema, table = schema_and_table(table)
274:         schema ||= opts[:schema]
275:         schema = im.call(schema) if schema
276:         table = im.call(table)
277:         indexes = {}
278:         metadata(:getIndexInfo, nil, schema, table, false, true) do |r|
279:           next unless name = r[:column_name]
280:           next if respond_to?(:primary_key_index_re, true) and r[:index_name] =~ primary_key_index_re 
281:           i = indexes[m.call(r[:index_name])] ||= {:columns=>[], :unique=>[false, 0].include?(r[:non_unique])}
282:           i[:columns] << m.call(name)
283:         end
284:         indexes
285:       end

Whether or not JNDI is being used for this connection.

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 288
288:       def jndi?
289:         !!(uri =~ JNDI_URI_REGEXP)
290:       end

Listens on the given channel (or multiple channels if channel is an array), waiting for notifications. After a notification is received, or the timeout has passed, stops listening to the channel. Options:

:after_listen :An object that responds to call that is called with the underlying connection after the LISTEN statement is sent, but before the connection starts waiting for notifications.
:loop :Whether to continually wait for notifications, instead of just waiting for a single notification. If this option is given, a block must be provided. If this object responds to call, it is called with the underlying connection after each notification is received (after the block is called). If a :timeout option is used, and a callable object is given, the object will also be called if the timeout expires. If :loop is used and you want to stop listening, you can either break from inside the block given to listen, or you can throw :stop from inside the :loop object‘s call method or the block.
:server :The server on which to listen, if the sharding support is being used.
:timeout :How long to wait for a notification, in seconds (can provide a float value for fractional seconds). If not given or nil, waits indefinitely.

This method is only supported if pg is used as the underlying ruby driver. It returns the channel the notification was sent to (as a string), unless :loop was used, in which case it returns nil. If a block is given, it is yielded 3 arguments:

  • the channel the notification was sent to (as a string)
  • the backend pid of the notifier (as an integer),
  • and the payload of the notification (as a string or nil).

[Source]

     # File lib/sequel/adapters/postgres.rb, line 359
359:         def listen(channels, opts={}, &block)
360:           check_database_errors do
361:             synchronize(opts[:server]) do |conn|
362:               begin
363:                 channels = Array(channels)
364:                 channels.each{|channel| conn.execute("LISTEN #{channel}")}
365:                 opts[:after_listen].call(conn) if opts[:after_listen]
366:                 timeout = opts[:timeout] ? [opts[:timeout]] : []
367:                 if l = opts[:loop]
368:                   raise Error, 'calling #listen with :loop requires a block' unless block
369:                   loop_call = l.respond_to?(:call)
370:                   catch(:stop) do
371:                     loop do
372:                       conn.wait_for_notify(*timeout, &block)
373:                       l.call(conn) if loop_call
374:                     end
375:                   end
376:                   nil
377:                 else
378:                   conn.wait_for_notify(*timeout, &block)
379:                 end
380:               ensure
381:                 conn.execute("UNLISTEN *")
382:               end
383:             end
384:           end
385:         end

Return the version of the MySQL server two which we are connecting.

[Source]

     # File lib/sequel/adapters/mysql.rb, line 159
159:       def server_version(server=nil)
160:         @server_version ||= (synchronize(server){|conn| conn.server_version if conn.respond_to?(:server_version)} || super)
161:       end

Run the given SQL with the given arguments and return the first value of the first row.

[Source]

     # File lib/sequel/adapters/sqlite.rb, line 107
107:       def single_value(sql, opts={})
108:         _execute(:single_value, sql, opts)
109:       end

Return the subadapter type for this database, i.e. sqlite3 for do:sqlite3::memory:.

[Source]

     # File lib/sequel/adapters/do.rb, line 104
104:       def subadapter
105:         uri.split(":").first
106:       end

All tables in this database

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 293
293:       def tables(opts={})
294:         get_tables('TABLE', opts)
295:       end

The uri for this connection. You can specify the uri using the :uri, :url, or :database options. You don‘t need to worry about this if you use Sequel.connect with the JDBC connectrion strings.

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 301
301:       def uri(opts={})
302:         opts = @opts.merge(opts)
303:         ur = opts[:uri] || opts[:url] || opts[:database]
304:         ur =~ /^\Ajdbc:/ ? ur : "jdbc:#{ur}"
305:       end

Return the DataObjects URI for the Sequel URI, removing the do: prefix.

[Source]

     # File lib/sequel/adapters/do.rb, line 110
110:       def uri(opts={})
111:         opts = @opts.merge(opts)
112:         (opts[:uri] || opts[:url]).sub(/\Ado:/, '')
113:       end

All views in this database

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 308
308:       def views(opts={})
309:         get_tables('VIEW', opts)
310:       end

2 - Methods that modify the database schema

These methods execute code on the database that modifies the database‘s schema.

Constants

AUTOINCREMENT = 'AUTOINCREMENT'.freeze
CASCADE = 'CASCADE'.freeze
COMMA_SEPARATOR = ', '.freeze
NO_ACTION = 'NO ACTION'.freeze
NOT_NULL = ' NOT NULL'.freeze
NULL = ' NULL'.freeze
PRIMARY_KEY = ' PRIMARY KEY'.freeze
RESTRICT = 'RESTRICT'.freeze
SET_DEFAULT = 'SET DEFAULT'.freeze
SET_NULL = 'SET NULL'.freeze
TEMPORARY = 'TEMPORARY '.freeze
UNDERSCORE = '_'.freeze
UNIQUE = ' UNIQUE'.freeze
UNSIGNED = ' UNSIGNED'.freeze
COLUMN_DEFINITION_ORDER = [:collate, :default, :null, :unique, :primary_key, :auto_increment, :references]   The order of column modifiers to use when defining a column.

Public Instance methods

Adds a column to the specified table. This method expects a column name, a datatype and optionally a hash with additional constraints and options:

  DB.add_column :items, :name, :text, :unique => true, :null => false
  DB.add_column :items, :category, :text, :default => 'ruby'

See alter_table.

[Source]

    # File lib/sequel/database/schema_methods.rb, line 33
33:     def add_column(table, *args)
34:       alter_table(table) {add_column(*args)}
35:     end

Adds an index to a table for the given columns:

  DB.add_index :posts, :title
  DB.add_index :posts, [:author, :title], :unique => true

Options:

:ignore_errors :Ignore any DatabaseErrors that are raised

See alter_table.

[Source]

    # File lib/sequel/database/schema_methods.rb, line 46
46:     def add_index(table, columns, options={})
47:       e = options[:ignore_errors]
48:       begin
49:         alter_table(table){add_index(columns, options)}
50:       rescue DatabaseError
51:         raise unless e
52:       end
53:     end

Alters the given table with the specified block. Example:

  DB.alter_table :items do
    add_column :category, :text, :default => 'ruby'
    drop_column :category
    rename_column :cntr, :counter
    set_column_type :value, :float
    set_column_default :value, :float
    add_index [:group, :category]
    drop_index [:group, :category]
  end

Note that add_column accepts all the options available for column definitions using create_table, and add_index accepts all the options available for index definition.

See Schema::AlterTableGenerator and the "Migrations and Schema Modification" guide.

[Source]

    # File lib/sequel/database/schema_methods.rb, line 72
72:     def alter_table(name, generator=nil, &block)
73:       generator ||= Schema::AlterTableGenerator.new(self, &block)
74:       remove_cached_schema(name)
75:       apply_alter_table(name, generator.operations)
76:       nil
77:     end

Creates a view, replacing it if it already exists:

  DB.create_or_replace_view(:cheap_items, "SELECT * FROM items WHERE price < 100")
  DB.create_or_replace_view(:ruby_items, DB[:items].filter(:category => 'ruby'))

[Source]

     # File lib/sequel/database/schema_methods.rb, line 130
130:     def create_or_replace_view(name, source)
131:       source = source.sql if source.is_a?(Dataset)
132:       execute_ddl("CREATE OR REPLACE VIEW #{quote_schema_table(name)} AS #{source}")
133:       remove_cached_schema(name)
134:       nil
135:     end

Creates a table with the columns given in the provided block:

  DB.create_table :posts do
    primary_key :id
    column :title, :text
    String :content
    index :title
  end

Options:

:temp :Create the table as a temporary table.
:ignore_index_errors :Ignore any errors when creating indexes.

See Schema::Generator and the "Migrations and Schema Modification" guide.

[Source]

     # File lib/sequel/database/schema_methods.rb, line 93
 93:     def create_table(name, options={}, &block)
 94:       remove_cached_schema(name)
 95:       options = {:generator=>options} if options.is_a?(Schema::Generator)
 96:       generator = options[:generator] || Schema::Generator.new(self, &block)
 97:       create_table_from_generator(name, generator, options)
 98:       create_table_indexes_from_generator(name, generator, options)
 99:       nil
100:     end

Forcibly create a table, attempting to drop it if it already exists, then creating it.

  DB.create_table!(:a){Integer :a}
  # SELECT * FROM a LIMIT a -- check existence
  # DROP TABLE a -- drop table if already exists
  # CREATE TABLE a (a integer)

[Source]

     # File lib/sequel/database/schema_methods.rb, line 108
108:     def create_table!(name, options={}, &block)
109:       drop_table(name) if table_exists?(name)
110:       create_table(name, options, &block)
111:     end

Creates the table unless the table already exists.

  DB.create_table?(:a){Integer :a}
  # SELECT * FROM a LIMIT a -- check existence
  # CREATE TABLE a (a integer) -- if it doesn't already exist

[Source]

     # File lib/sequel/database/schema_methods.rb, line 118
118:     def create_table?(name, options={}, &block)
119:       if supports_create_table_if_not_exists?
120:         create_table(name, options.merge(:if_not_exists=>true), &block)
121:       elsif !table_exists?(name)
122:         create_table(name, options, &block)
123:       end
124:     end

Creates a view based on a dataset or an SQL string:

  DB.create_view(:cheap_items, "SELECT * FROM items WHERE price < 100")
  DB.create_view(:ruby_items, DB[:items].filter(:category => 'ruby'))

[Source]

     # File lib/sequel/database/schema_methods.rb, line 141
141:     def create_view(name, source)
142:       source = source.sql if source.is_a?(Dataset)
143:       execute_ddl("CREATE VIEW #{quote_schema_table(name)} AS #{source}")
144:     end

Removes a column from the specified table:

  DB.drop_column :items, :category

See alter_table.

[Source]

     # File lib/sequel/database/schema_methods.rb, line 151
151:     def drop_column(table, *args)
152:       alter_table(table) {drop_column(*args)}
153:     end

Removes an index for the given table and column/s:

  DB.drop_index :posts, :title
  DB.drop_index :posts, [:author, :title]

See alter_table.

[Source]

     # File lib/sequel/database/schema_methods.rb, line 161
161:     def drop_index(table, columns, options={})
162:       alter_table(table){drop_index(columns, options)}
163:     end

Drops one or more tables corresponding to the given names:

  DB.drop_table(:posts)
  DB.drop_table(:posts, :comments)
  DB.drop_table(:posts, :comments, :cascade=>true)

[Source]

     # File lib/sequel/database/schema_methods.rb, line 170
170:     def drop_table(*names)
171:       options = names.last.is_a?(Hash) ? names.pop : {}
172:       names.each do |n|
173:         execute_ddl(drop_table_sql(n, options))
174:         remove_cached_schema(n)
175:       end
176:       nil
177:     end

Drops one or more views corresponding to the given names:

  DB.drop_view(:cheap_items)
  DB.drop_view(:cheap_items, :pricey_items)
  DB.drop_view(:cheap_items, :pricey_items, :cascade=>true)

[Source]

     # File lib/sequel/database/schema_methods.rb, line 184
184:     def drop_view(*names)
185:       options = names.last.is_a?(Hash) ? names.pop : {}
186:       names.each do |n|
187:         execute_ddl(drop_view_sql(n, options))
188:         remove_cached_schema(n)
189:       end
190:       nil
191:     end

Renames a column in the specified table. This method expects the current column name and the new column name:

  DB.rename_column :items, :cntr, :counter

See alter_table.

[Source]

     # File lib/sequel/database/schema_methods.rb, line 210
210:     def rename_column(table, *args)
211:       alter_table(table) {rename_column(*args)}
212:     end

Renames a table:

  DB.tables #=> [:items]
  DB.rename_table :items, :old_items
  DB.tables #=> [:old_items]

[Source]

     # File lib/sequel/database/schema_methods.rb, line 198
198:     def rename_table(name, new_name)
199:       execute_ddl(rename_table_sql(name, new_name))
200:       remove_cached_schema(name)
201:       nil
202:     end

Sets the default value for the given column in the given table:

  DB.set_column_default :items, :category, 'perl!'

See alter_table.

[Source]

     # File lib/sequel/database/schema_methods.rb, line 219
219:     def set_column_default(table, *args)
220:       alter_table(table) {set_column_default(*args)}
221:     end

Set the data type for the given column in the given table:

  DB.set_column_type :items, :price, :float

See alter_table.

[Source]

     # File lib/sequel/database/schema_methods.rb, line 228
228:     def set_column_type(table, *args)
229:       alter_table(table) {set_column_type(*args)}
230:     end

4 - Methods relating to adapters, connecting, disconnecting, and sharding

This methods involve the Database‘s connection pool.

Constants

ADAPTERS = %w'ado amalgalite db2 dbi do firebird ibmdb informix jdbc mock mysql mysql2 odbc openbase oracle postgres sqlite swift tinytds'.collect{|x| x.to_sym}   Array of supported database adapters

Attributes

pool  [R]  The connection pool for this Database instance. All Database instances have their own connection pools.

Public Class methods

The Database subclass for the given adapter scheme. Raises Sequel::AdapterNotFound if the adapter could not be loaded.

[Source]

    # File lib/sequel/database/connecting.rb, line 17
17:     def self.adapter_class(scheme)
18:       return scheme if scheme.is_a?(Class)
19: 
20:       scheme = scheme.to_s.gsub('-', '_').to_sym
21:       
22:       unless klass = ADAPTER_MAP[scheme]
23:         # attempt to load the adapter file
24:         begin
25:           Sequel.tsk_require "sequel/adapters/#{scheme}"
26:         rescue LoadError => e
27:           raise Sequel.convert_exception_class(e, AdapterNotFound)
28:         end
29:         
30:         # make sure we actually loaded the adapter
31:         unless klass = ADAPTER_MAP[scheme]
32:           raise AdapterNotFound, "Could not load #{scheme} adapter: adapter class not registered in ADAPTER_MAP"
33:         end
34:       end
35:       klass
36:     end

Returns the scheme symbol for the Database class.

[Source]

    # File lib/sequel/database/connecting.rb, line 39
39:     def self.adapter_scheme
40:       @scheme
41:     end

Connects to a database. See Sequel.connect.

[Source]

    # File lib/sequel/database/connecting.rb, line 44
44:     def self.connect(conn_string, opts = {})
45:       case conn_string
46:       when String
47:         if match = /\A(jdbc|do):/o.match(conn_string)
48:           c = adapter_class(match[1].to_sym)
49:           opts = {:uri=>conn_string}.merge(opts)
50:         else
51:           uri = URI.parse(conn_string)
52:           scheme = uri.scheme
53:           scheme = :dbi if scheme =~ /\Adbi-/
54:           c = adapter_class(scheme)
55:           uri_options = c.send(:uri_to_options, uri)
56:           uri.query.split('&').collect{|s| s.split('=')}.each{|k,v| uri_options[k.to_sym] = v if k && !k.empty?} unless uri.query.to_s.strip.empty?
57:           uri_options.to_a.each{|k,v| uri_options[k] = URI.unescape(v) if v.is_a?(String)}
58:           opts = uri_options.merge(opts)
59:           opts[:adapter] = scheme
60:         end
61:       when Hash
62:         opts = conn_string.merge(opts)
63:         c = adapter_class(opts[:adapter_class] || opts[:adapter] || opts['adapter'])
64:       else
65:         raise Error, "Sequel::Database.connect takes either a Hash or a String, given: #{conn_string.inspect}"
66:       end
67:       # process opts a bit
68:       opts = opts.inject({}) do |m, (k,v)|
69:         k = :user if k.to_s == 'username'
70:         m[k.to_sym] = v
71:         m
72:       end
73:       begin
74:         db = c.new(opts)
75:         db.test_connection if opts[:test] && db.send(:typecast_value_boolean, opts[:test])
76:         result = yield(db) if block_given?
77:       ensure
78:         if block_given?
79:           db.disconnect if db
80:           ::Sequel::DATABASES.delete(db)
81:         end
82:       end
83:       block_given? ? result : db
84:     end

Sets the default single_threaded mode for new databases. See Sequel.single_threaded=.

[Source]

    # File lib/sequel/database/connecting.rb, line 88
88:     def self.single_threaded=(value)
89:       @@single_threaded = value
90:     end

Public Instance methods

Returns the scheme symbol for this instance‘s class, which reflects which adapter is being used. In some cases, this can be the same as the database_type (for native adapters), in others (i.e. adapters with subadapters), it will be different.

  Sequel.connect('jdbc:postgres://...').adapter_scheme # => :jdbc

[Source]

     # File lib/sequel/database/connecting.rb, line 120
120:     def adapter_scheme
121:       self.class.adapter_scheme
122:     end

Dynamically add new servers or modify server options at runtime. Also adds new servers to the connection pool. Intended for use with master/slave or shard configurations where it is useful to add new server hosts at runtime.

servers argument should be a hash with server name symbol keys and hash or proc values. If a servers key is already in use, it‘s value is overridden with the value provided.

  DB.add_servers(:f=>{:host=>"hash_host_f"})

[Source]

     # File lib/sequel/database/connecting.rb, line 133
133:     def add_servers(servers)
134:       @opts[:servers] = @opts[:servers] ? @opts[:servers].merge(servers) : servers
135:       @pool.add_servers(servers.keys)
136:     end

Connects to the database. This method should be overridden by descendants.

[Source]

     # File lib/sequel/database/connecting.rb, line 139
139:     def connect(server)
140:       raise NotImplemented, "#connect should be overridden by adapters"
141:     end

The database type for this database object, the same as the adapter scheme by default. Should be overridden in adapters (especially shared adapters) to be the correct type, so that even if two separate Database objects are using different adapters you can tell that they are using the same database type. Even better, you can tell that two Database objects that are using the same adapter are connecting to different database types (think JDBC or DataObjects).

  Sequel.connect('jdbc:postgres://...').database_type # => :postgres

[Source]

     # File lib/sequel/database/connecting.rb, line 152
152:     def database_type
153:       adapter_scheme
154:     end

Disconnects all available connections from the connection pool. Any connections currently in use will not be disconnected. Options:

:servers :Should be a symbol specifing the server to disconnect from, or an array of symbols to specify multiple servers.

Example:

  DB.disconnect # All servers
  DB.disconnect(:servers=>:server1) # Single server
  DB.disconnect(:servers=>[:server1, :server2]) # Multiple servers

[Source]

     # File lib/sequel/database/connecting.rb, line 166
166:     def disconnect(opts = {})
167:       pool.disconnect(opts)
168:     end

Yield a new Database instance for every server in the connection pool. Intended for use in sharded environments where there is a need to make schema modifications (DDL queries) on each shard.

  DB.each_server{|db| db.create_table(:users){primary_key :id; String :name}}

[Source]

     # File lib/sequel/database/connecting.rb, line 175
175:     def each_server(&block)
176:       servers.each{|s| self.class.connect(server_opts(s), &block)}
177:     end

Dynamically remove existing servers from the connection pool. Intended for use with master/slave or shard configurations where it is useful to remove existing server hosts at runtime.

servers should be symbols or arrays of symbols. If a nonexistent server is specified, it is ignored. If no servers have been specified for this database, no changes are made. If you attempt to remove the :default server, an error will be raised.

  DB.remove_servers(:f1, :f2)

[Source]

     # File lib/sequel/database/connecting.rb, line 189
189:     def remove_servers(*servers)
190:       if @opts[:servers] && !@opts[:servers].empty?
191:         servs = @opts[:servers].dup
192:         servers.flatten!
193:         servers.each{|s| servs.delete(s)}
194:         @opts[:servers] = servs
195:         @pool.remove_servers(servers)
196:       end
197:     end

An array of servers/shards for this Database object.

  DB.servers # Unsharded: => [:default]
  DB.servers # Sharded:   => [:default, :server1, :server2]

[Source]

     # File lib/sequel/database/connecting.rb, line 203
203:     def servers
204:       pool.servers
205:     end

Returns true if the database is using a single-threaded connection pool.

[Source]

     # File lib/sequel/database/connecting.rb, line 208
208:     def single_threaded?
209:       @single_threaded
210:     end

Acquires a database connection, yielding it to the passed block. This is useful if you want to make sure the same connection is used for all database queries in the block. It is also useful if you want to gain direct access to the underlying connection object if you need to do something Sequel does not natively support.

If a server option is given, acquires a connection for that specific server, instead of the :default server.

  DB.synchronize do |conn|
    ...
  end

[Source]

     # File lib/sequel/database/connecting.rb, line 224
224:     def synchronize(server=nil, &block)
225:       @pool.hold(server || :default, &block)
226:     end

Attempts to acquire a database connection. Returns true if successful. Will probably raise an Error if unsuccessful. If a server argument is given, attempts to acquire a database connection to the given server/shard.

[Source]

     # File lib/sequel/database/connecting.rb, line 232
232:     def test_connection(server=nil)
233:       synchronize(server){|conn|}
234:       true
235:     end

3 - Methods that create datasets

These methods all return instances of this database‘s dataset class.

Public Instance methods

Returns a dataset for the database. If the first argument is a string, the method acts as an alias for Database#fetch, returning a dataset for arbitrary SQL, with or without placeholders:

  DB['SELECT * FROM items'].all
  DB['SELECT * FROM items WHERE name = ?', my_name].all

Otherwise, acts as an alias for Database#from, setting the primary table for the dataset:

  DB[:items].sql #=> "SELECT * FROM items"

[Source]

    # File lib/sequel/database/dataset.rb, line 19
19:     def [](*args)
20:       (String === args.first) ? fetch(*args) : from(*args)
21:     end

Returns a blank dataset for this database.

  DB.dataset # SELECT *
  DB.dataset.from(:items) # SELECT * FROM items

[Source]

    # File lib/sequel/database/dataset.rb, line 27
27:     def dataset(opts=nil)
28:       @dataset_class.new(self, opts)
29:     end

Fetches records for an arbitrary SQL statement. If a block is given, it is used to iterate over the records:

  DB.fetch('SELECT * FROM items'){|r| p r}

The fetch method returns a dataset instance:

  DB.fetch('SELECT * FROM items').all

fetch can also perform parameterized queries for protection against SQL injection:

  DB.fetch('SELECT * FROM items WHERE name = ?', my_name).all

[Source]

    # File lib/sequel/database/dataset.rb, line 44
44:     def fetch(sql, *args, &block)
45:       ds = dataset.with_sql(sql, *args)
46:       ds.each(&block) if block
47:       ds
48:     end

Returns a new dataset with the from method invoked. If a block is given, it is used as a filter on the dataset.

  DB.from(:items) # SELECT * FROM items
  DB.from(:items){id > 2} # SELECT * FROM items WHERE (id > 2)

[Source]

    # File lib/sequel/database/dataset.rb, line 55
55:     def from(*args, &block)
56:       ds = dataset.from(*args)
57:       block ? ds.filter(&block) : ds
58:     end

Returns a new dataset with the select method invoked.

  DB.select(1) # SELECT 1
  DB.select{server_version{}} # SELECT server_version()
  DB.select(:id).from(:items) # SELECT id FROM items

[Source]

    # File lib/sequel/database/dataset.rb, line 65
65:     def select(*args, &block)
66:       dataset.select(*args, &block)
67:     end

5 - Methods that set defaults for created datasets

This methods change the default behavior of this database‘s datasets.

Constants

DatasetClass = Sequel::Dataset   The default class to use for datasets

Attributes

dataset_class  [R]  The class to use for creating datasets. Should respond to new with the Database argument as the first argument, and an optional options hash.
default_schema  [RW]  The default schema to use, generally should be nil.

Public Class methods

The method to call on identifiers going into the database

[Source]

    # File lib/sequel/database/dataset_defaults.rb, line 21
21:     def self.identifier_input_method
22:       @@identifier_input_method
23:     end

Set the method to call on identifiers going into the database See Sequel.identifier_input_method=.

[Source]

    # File lib/sequel/database/dataset_defaults.rb, line 27
27:     def self.identifier_input_method=(v)
28:       @@identifier_input_method = v || ""
29:     end

The method to call on identifiers coming from the database

[Source]

    # File lib/sequel/database/dataset_defaults.rb, line 32
32:     def self.identifier_output_method
33:       @@identifier_output_method
34:     end

Set the method to call on identifiers coming from the database See Sequel.identifier_output_method=.

[Source]

    # File lib/sequel/database/dataset_defaults.rb, line 38
38:     def self.identifier_output_method=(v)
39:       @@identifier_output_method = v || ""
40:     end

Sets the default quote_identifiers mode for new databases. See Sequel.quote_identifiers=.

[Source]

    # File lib/sequel/database/dataset_defaults.rb, line 44
44:     def self.quote_identifiers=(value)
45:       @@quote_identifiers = value
46:     end

Public Instance methods

If the database has any dataset modules associated with it, use a subclass of the given class that includes the modules as the dataset class.

[Source]

    # File lib/sequel/database/dataset_defaults.rb, line 59
59:     def dataset_class=(c)
60:       unless @dataset_modules.empty?
61:         c = Class.new(c)
62:         @dataset_modules.each{|m| c.send(:include, m)}
63:       end
64:       @dataset_class = c
65:     end

Equivalent to extending all datasets produced by the database with a module. What it actually does is use a subclass of the current dataset_class as the new dataset_class, and include the module in the subclass. Instead of a module, you can provide a block that is used to create an anonymous module.

This allows you to override any of the dataset methods even if they are defined directly on the dataset class that this Database object uses.

Examples:

  # Introspec columns for all of DB's datasets
  DB.extend_datasets(Sequel::ColumnsIntrospection)

  # Trace all SELECT queries by printing the SQL and the full backtrace
  DB.extend_datasets do
    def fetch_rows(sql)
      puts sql
      puts caller
      super
    end
  end

[Source]

    # File lib/sequel/database/dataset_defaults.rb, line 89
89:     def extend_datasets(mod=nil, &block)
90:       raise(Error, "must provide either mod or block, not both") if mod && block
91:       mod = Module.new(&block) if block
92:       if @dataset_modules.empty?
93:        @dataset_modules = [mod]
94:        @dataset_class = Class.new(@dataset_class)
95:       else
96:        @dataset_modules << mod
97:       end
98:       @dataset_class.send(:include, mod)
99:     end

The method to call on identifiers going into the database

[Source]

     # File lib/sequel/database/dataset_defaults.rb, line 102
102:     def identifier_input_method
103:       case @identifier_input_method
104:       when nil
105:         @identifier_input_method = @opts.fetch(:identifier_input_method, (@@identifier_input_method.nil? ? identifier_input_method_default : @@identifier_input_method))
106:         @identifier_input_method == "" ? nil : @identifier_input_method
107:       when ""
108:         nil
109:       else
110:         @identifier_input_method
111:       end
112:     end

Set the method to call on identifiers going into the database:

  DB[:items] # SELECT * FROM items
  DB.identifier_input_method = :upcase
  DB[:items] # SELECT * FROM ITEMS

[Source]

     # File lib/sequel/database/dataset_defaults.rb, line 119
119:     def identifier_input_method=(v)
120:       reset_schema_utility_dataset
121:       @identifier_input_method = v || ""
122:     end

The method to call on identifiers coming from the database

[Source]

     # File lib/sequel/database/dataset_defaults.rb, line 125
125:     def identifier_output_method
126:       case @identifier_output_method
127:       when nil
128:         @identifier_output_method = @opts.fetch(:identifier_output_method, (@@identifier_output_method.nil? ? identifier_output_method_default : @@identifier_output_method))
129:         @identifier_output_method == "" ? nil : @identifier_output_method
130:       when ""
131:         nil
132:       else
133:         @identifier_output_method
134:       end
135:     end

Set the method to call on identifiers coming from the database:

  DB[:items].first # {:id=>1, :name=>'foo'}
  DB.identifier_output_method = :upcase
  DB[:items].first # {:ID=>1, :NAME=>'foo'}

[Source]

     # File lib/sequel/database/dataset_defaults.rb, line 142
142:     def identifier_output_method=(v)
143:       reset_schema_utility_dataset
144:       @identifier_output_method = v || ""
145:     end

Set whether to quote identifiers (columns and tables) for this database:

  DB[:items] # SELECT * FROM items
  DB.quote_identifiers = true
  DB[:items] # SELECT * FROM "items"

[Source]

     # File lib/sequel/database/dataset_defaults.rb, line 152
152:     def quote_identifiers=(v)
153:       reset_schema_utility_dataset
154:       @quote_identifiers = v
155:     end

Returns true if the database quotes identifiers.

[Source]

     # File lib/sequel/database/dataset_defaults.rb, line 158
158:     def quote_identifiers?
159:       return @quote_identifiers unless @quote_identifiers.nil?
160:       @quote_identifiers = @opts.fetch(:quote_identifiers, (@@quote_identifiers.nil? ? quote_identifiers_default : @@quote_identifiers))
161:     end

6 - Methods relating to logging

This methods affect relating to the logging of executed SQL.

Attributes

log_warn_duration  [RW]  Numeric specifying the duration beyond which queries are logged at warn level instead of info level.
loggers  [RW]  Array of SQL loggers to use for this database.
sql_log_level  [RW]  Log level at which to log SQL queries. This is actually the method sent to the logger, so it should be the method name symbol. The default is :info, it can be set to :debug to log at DEBUG level.

Public Instance methods

Log a message at level info to all loggers.

[Source]

    # File lib/sequel/database/logging.rb, line 21
21:     def log_info(message, args=nil)
22:       log_each(:info, args ? "#{message}; #{args.inspect}" : message)
23:     end

Yield to the block, logging any errors at error level to all loggers, and all other queries with the duration at warn or info level.

[Source]

    # File lib/sequel/database/logging.rb, line 27
27:     def log_yield(sql, args=nil)
28:       return yield if @loggers.empty?
29:       sql = "#{sql}; #{args.inspect}" if args
30:       start = Time.now
31:       begin
32:         yield
33:       rescue => e
34:         log_each(:error, "#{e.class}: #{e.message.strip}: #{sql}")
35:         raise
36:       ensure
37:         log_duration(Time.now - start, sql) unless e
38:       end
39:     end

Remove any existing loggers and just use the given logger:

  DB.logger = Logger.new($stdout)

[Source]

    # File lib/sequel/database/logging.rb, line 44
44:     def logger=(logger)
45:       @loggers = Array(logger)
46:     end

7 - Miscellaneous methods

These methods don‘t fit neatly into another category.

Constants

LEADING_ZERO_RE = /\A0+(\d)/.freeze   Used for checking/removing leading zeroes from strings so they don‘t get interpreted as octal.
LEADING_ZERO_REP = "\\1".freeze   Replacement string when replacing leading zeroes.

Attributes

opts  [R]  The options hash for this database
timezone  [W]  Set the timezone to use for this database, overridding Sequel.database_timezone.

Public Class methods

Constructs a new instance of a database connection with the specified options hash.

Accepts the following options:

:default_schema :The default schema to use, should generally be nil
:disconnection_proc :A proc used to disconnect the connection
:identifier_input_method :A string method symbol to call on identifiers going into the database
:identifier_output_method :A string method symbol to call on identifiers coming from the database
:logger :A specific logger to use
:loggers :An array of loggers to use
:quote_identifiers :Whether to quote identifiers
:servers :A hash specifying a server/shard specific options, keyed by shard symbol
:single_threaded :Whether to use a single-threaded connection pool
:sql_log_level :Method to use to log SQL to a logger, :info by default.

All options given are also passed to the connection pool. If a block is given, it is used as the connection_proc for the ConnectionPool.

[Source]

    # File lib/sequel/database/misc.rb, line 42
42:     def initialize(opts = {}, &block)
43:       @opts ||= opts
44:       @opts = connection_pool_default_options.merge(@opts)
45:       @loggers = Array(@opts[:logger]) + Array(@opts[:loggers])
46:       self.log_warn_duration = @opts[:log_warn_duration]
47:       @opts[:disconnection_proc] ||= proc{|conn| disconnect_connection(conn)}
48:       block ||= proc{|server| connect(server)}
49:       @opts[:servers] = {} if @opts[:servers].is_a?(String)
50:       @opts[:adapter_class] = self.class
51:       
52:       @opts[:single_threaded] = @single_threaded = typecast_value_boolean(@opts.fetch(:single_threaded, @@single_threaded))
53:       @schemas = {}
54:       @default_schema = @opts.fetch(:default_schema, default_schema_default)
55:       @prepared_statements = {}
56:       @transactions = {}
57:       @identifier_input_method = nil
58:       @identifier_output_method = nil
59:       @quote_identifiers = nil
60:       @timezone = nil
61:       @dataset_class = dataset_class_default
62:       @dataset_modules = []
63:       self.sql_log_level = @opts[:sql_log_level] ? @opts[:sql_log_level].to_sym : :info
64:       @pool = ConnectionPool.get_pool(@opts, &block)
65: 
66:       ::Sequel::DATABASES.push(self)
67:     end

Public Instance methods

If a transaction is not currently in process, yield to the block immediately. Otherwise, add the block to the list of blocks to call after the currently in progress transaction commits (and only if it commits). Options:

:server :The server/shard to use.

[Source]

    # File lib/sequel/database/misc.rb, line 74
74:     def after_commit(opts={}, &block)
75:       raise Error, "must provide block to after_commit" unless block
76:       synchronize(opts[:server]) do |conn|
77:         if h = @transactions[conn]
78:           raise Error, "cannot call after_commit in a prepared transaction" if h[:prepare]
79:           (h[:after_commit] ||= []) << block
80:         else
81:           yield
82:         end
83:       end
84:     end

If a transaction is not currently in progress, ignore the block. Otherwise, add the block to the list of the blocks to call after the currently in progress transaction rolls back (and only if it rolls back). Options:

:server :The server/shard to use.

[Source]

    # File lib/sequel/database/misc.rb, line 91
91:     def after_rollback(opts={}, &block)
92:       raise Error, "must provide block to after_rollback" unless block
93:       synchronize(opts[:server]) do |conn|
94:         if h = @transactions[conn]
95:           raise Error, "cannot call after_rollback in a prepared transaction" if h[:prepare]
96:           (h[:after_rollback] ||= []) << block
97:         end
98:       end
99:     end

Cast the given type to a literal type

  DB.cast_type_literal(Float) # double precision
  DB.cast_type_literal(:foo) # foo

[Source]

     # File lib/sequel/database/misc.rb, line 105
105:     def cast_type_literal(type)
106:       type_literal(:type=>type)
107:     end

Convert the given timestamp from the application‘s timezone, to the databases‘s timezone or the default database timezone if the database does not have a timezone.

[Source]

     # File lib/sequel/database/misc.rb, line 112
112:     def from_application_timestamp(v)
113:       Sequel.convert_output_timestamp(v, timezone)
114:     end

Return true if already in a transaction given the options, false otherwise. Respects the :server option for selecting a shard.

[Source]

     # File lib/sequel/database/misc.rb, line 119
119:     def in_transaction?(opts={})
120:       synchronize(opts[:server]){|conn| !!@transactions[conn]}
121:     end

Returns a string representation of the database object including the class name and the connection URI (or the opts if the URI cannot be constructed).

[Source]

     # File lib/sequel/database/misc.rb, line 126
126:     def inspect
127:       "#<#{self.class}: #{(uri rescue opts).inspect}>" 
128:     end

Proxy the literal call to the dataset.

  DB.literal(1) # 1
  DB.literal(:a) # a
  DB.literal('a') # 'a'

[Source]

     # File lib/sequel/database/misc.rb, line 135
135:     def literal(v)
136:       schema_utility_dataset.literal(v)
137:     end

Default serial primary key options, used by the table creation code.

[Source]

     # File lib/sequel/database/misc.rb, line 141
141:     def serial_primary_key_options
142:       {:primary_key => true, :type => Integer, :auto_increment => true}
143:     end

Whether the database supports CREATE TABLE IF NOT EXISTS syntax, false by default.

[Source]

     # File lib/sequel/database/misc.rb, line 147
147:     def supports_create_table_if_not_exists?
148:       false
149:     end

Whether the database and adapter support prepared transactions (two-phase commit), false by default.

[Source]

     # File lib/sequel/database/misc.rb, line 153
153:     def supports_prepared_transactions?
154:       false
155:     end

Whether the database and adapter support savepoints, false by default.

[Source]

     # File lib/sequel/database/misc.rb, line 158
158:     def supports_savepoints?
159:       false
160:     end

Whether the database and adapter support transaction isolation levels, false by default.

[Source]

     # File lib/sequel/database/misc.rb, line 163
163:     def supports_transaction_isolation_levels?
164:       false
165:     end

The timezone to use for this database, defaulting to Sequel.database_timezone.

[Source]

     # File lib/sequel/database/misc.rb, line 168
168:     def timezone
169:       @timezone || Sequel.database_timezone
170:     end

Convert the given timestamp to the application‘s timezone, from the databases‘s timezone or the default database timezone if the database does not have a timezone.

[Source]

     # File lib/sequel/database/misc.rb, line 175
175:     def to_application_timestamp(v)
176:       Sequel.convert_timestamp(v, timezone)
177:     end

Typecast the value to the given column_type. Calls typecast_value_#{column_type} if the method exists, otherwise returns the value. This method should raise Sequel::InvalidValue if assigned value is invalid.

[Source]

     # File lib/sequel/database/misc.rb, line 184
184:     def typecast_value(column_type, value)
185:       return nil if value.nil?
186:       meth = "typecast_value_#{column_type}"
187:       begin
188:         respond_to?(meth, true) ? send(meth, value) : value
189:       rescue ArgumentError, TypeError => e
190:         raise Sequel.convert_exception_class(e, InvalidValue)
191:       end
192:     end

Returns the URI identifying the database, which may not be the same as the URI used when connecting. This method can raise an error if the database used options instead of a connection string, and will not include uri parameters.

  Sequel.connect('postgres://localhost/db?user=billg').url
  # => "postgres://billg@localhost/db"

[Source]

     # File lib/sequel/database/misc.rb, line 202
202:     def uri
203:       uri = URI::Generic.new(
204:         adapter_scheme.to_s,
205:         nil,
206:         @opts[:host],
207:         @opts[:port],
208:         nil,
209:         "/#{@opts[:database]}",
210:         nil,
211:         nil,
212:         nil
213:       )
214:       uri.user = @opts[:user]
215:       uri.password = @opts[:password] if uri.user
216:       uri.to_s
217:     end

Explicit alias of uri for easier subclassing.

[Source]

     # File lib/sequel/database/misc.rb, line 220
220:     def url
221:       uri
222:     end

1 - Methods that execute queries and/or return results

This methods generally execute SQL code on the database server.

Constants

SQL_BEGIN = 'BEGIN'.freeze
SQL_COMMIT = 'COMMIT'.freeze
SQL_RELEASE_SAVEPOINT = 'RELEASE SAVEPOINT autopoint_%d'.freeze
SQL_ROLLBACK = 'ROLLBACK'.freeze
SQL_ROLLBACK_TO_SAVEPOINT = 'ROLLBACK TO SAVEPOINT autopoint_%d'.freeze
SQL_SAVEPOINT = 'SAVEPOINT autopoint_%d'.freeze
TRANSACTION_BEGIN = 'Transaction.begin'.freeze
TRANSACTION_COMMIT = 'Transaction.commit'.freeze
TRANSACTION_ROLLBACK = 'Transaction.rollback'.freeze
TRANSACTION_ISOLATION_LEVELS = {:uncommitted=>'READ UNCOMMITTED'.freeze, :committed=>'READ COMMITTED'.freeze, :repeatable=>'REPEATABLE READ'.freeze, :serializable=>'SERIALIZABLE'.freeze}
POSTGRES_DEFAULT_RE = /\A(?:B?('.*')::[^']+|\((-?\d+(?:\.\d+)?)\))\z/
MSSQL_DEFAULT_RE = /\A(?:\(N?('.*')\)|\(\((-?\d+(?:\.\d+)?)\)\))\z/
MYSQL_TIMESTAMP_RE = /\ACURRENT_(?:DATE|TIMESTAMP)?\z/
STRING_DEFAULT_RE = /\A'(.*)'\z/

Attributes

prepared_statements  [R]  The prepared statement object hash for this database, keyed by name symbol
transaction_isolation_level  [RW]  The default transaction isolation level for this database, used for all future transactions. For MSSQL, this should be set to something if you ever plan to use the :isolation option to Database#transaction, as on MSSQL if affects all future transactions on the same connection.

Public Instance methods

Runs the supplied SQL statement string on the database server. Returns self so it can be safely chained:

  DB << "UPADTE albums SET artist_id = NULL" << "DROP TABLE artists"

[Source]

    # File lib/sequel/database/query.rb, line 43
43:     def <<(sql)
44:       run(sql)
45:       self
46:     end

Call the prepared statement with the given name with the given hash of arguments.

  DB[:items].filter(:id=>1).prepare(:first, :sa)
  DB.call(:sa) # SELECT * FROM items WHERE id = 1

[Source]

    # File lib/sequel/database/query.rb, line 53
53:     def call(ps_name, hash={})
54:       prepared_statements[ps_name].call(hash)
55:     end

Dump indexes for all tables as a migration. This complements the :indexes=>false option to dump_schema_migration. Options:

  • :same_db - Create a dump for the same database type, so don‘t ignore errors if the index statements fail.

[Source]

    # File lib/sequel/extensions/schema_dumper.rb, line 13
13:     def dump_indexes_migration(options={})
14:       ts = tables(options)
15:       "Sequel.migration do\n  up do\n\#{ts.sort_by{|t| t.to_s}.map{|t| dump_table_indexes(t, :add_index, options)}.reject{|x| x == ''}.join(\"\\n\\n\").gsub(/^/o, '    ')}\n  end\n  \n  down do\n\#{ts.sort_by{|t| t.to_s}.map{|t| dump_table_indexes(t, :drop_index, options)}.reject{|x| x == ''}.join(\"\\n\\n\").gsub(/^/o, '    ')}\n  end\nend\n"
16:     end

Return a string that contains a Sequel::Migration subclass that when run would recreate the database structure. Options:

  • :same_db - Don‘t attempt to translate database types to ruby types. If this isn‘t set to true, all database types will be translated to ruby types, but there is no guarantee that the migration generated will yield the same type. Without this set, types that aren‘t recognized will be translated to a string-like type.
  • :indexes - If set to false, don‘t dump indexes (they can be added later via dump_index_migration).

[Source]

    # File lib/sequel/extensions/schema_dumper.rb, line 38
38:     def dump_schema_migration(options={})
39:       ts = tables(options)
40:       "Sequel.migration do\n  up do\n\#{ts.sort_by{|t| t.to_s}.map{|t| dump_table_schema(t, options)}.join(\"\\n\\n\").gsub(/^/o, '    ')}\n  end\n  \n  down do\n    drop_table(\#{ts.sort_by{|t| t.to_s}.inspect[1...-1]})\n  end\nend\n"
41:     end

Return a string with a create table block that will recreate the given table‘s schema. Takes the same options as dump_schema_migration.

[Source]

    # File lib/sequel/extensions/schema_dumper.rb, line 56
56:     def dump_table_schema(table, options={})
57:       table = table.value.to_s if table.is_a?(SQL::Identifier)
58:       raise(Error, "must provide table as a Symbol, String, or Sequel::SQL::Identifier") unless [String, Symbol].any?{|c| table.is_a?(c)}
59:       s = schema(table).dup
60:       pks = s.find_all{|x| x.last[:primary_key] == true}.map{|x| x.first}
61:       options = options.merge(:single_pk=>true) if pks.length == 1
62:       m = method(:column_schema_to_generator_opts)
63:       im = method(:index_to_generator_opts)
64:       begin
65:         indexes = indexes(table).sort_by{|k,v| k.to_s} if options[:indexes] != false
66:       rescue Sequel::NotImplemented
67:         nil
68:       end
69:       gen = Schema::Generator.new(self) do
70:         s.each{|name, info| send(*m.call(name, info, options))}
71:         primary_key(pks) if !@primary_key && pks.length > 0
72:         indexes.each{|iname, iopts| send(:index, iopts[:columns], im.call(table, iname, iopts))} if indexes
73:       end
74:       commands = [gen.dump_columns, gen.dump_constraints, gen.dump_indexes].reject{|x| x == ''}.join("\n\n")
75:       "create_table(#{table.inspect}#{', :ignore_index_errors=>true' if !options[:same_db] && options[:indexes] != false && indexes && !indexes.empty?}) do\n#{commands.gsub(/^/o, '  ')}\nend"
76:     end

Executes the given SQL on the database. This method should be overridden in descendants. This method should not be called directly by user code.

[Source]

    # File lib/sequel/database/query.rb, line 59
59:     def execute(sql, opts={})
60:       raise NotImplemented, "#execute should be overridden by adapters"
61:     end

Method that should be used when submitting any DDL (Data Definition Language) SQL, such as create_table. By default, calls execute_dui. This method should not be called directly by user code.

[Source]

    # File lib/sequel/database/query.rb, line 66
66:     def execute_ddl(sql, opts={}, &block)
67:       execute_dui(sql, opts, &block)
68:     end

Method that should be used when issuing a DELETE, UPDATE, or INSERT statement. By default, calls execute. This method should not be called directly by user code.

[Source]

    # File lib/sequel/database/query.rb, line 73
73:     def execute_dui(sql, opts={}, &block)
74:       execute(sql, opts, &block)
75:     end

Method that should be used when issuing a INSERT statement. By default, calls execute_dui. This method should not be called directly by user code.

[Source]

    # File lib/sequel/database/query.rb, line 80
80:     def execute_insert(sql, opts={}, &block)
81:       execute_dui(sql, opts, &block)
82:     end

Returns a single value from the database, e.g.:

  DB.get(1) # SELECT 1
  # => 1
  DB.get{server_version{}} # SELECT server_version()

[Source]

    # File lib/sequel/database/query.rb, line 89
89:     def get(*args, &block)
90:       dataset.get(*args, &block)
91:     end

Return a hash containing index information for the table. Hash keys are index name symbols. Values are subhashes with two keys, :columns and :unique. The value of :columns is an array of symbols of column names. The value of :unique is true or false depending on if the index is unique.

Should not include the primary key index, functional indexes, or partial indexes.

  DB.indexes(:artists)
  # => {:artists_name_ukey=>{:columns=>[:name], :unique=>true}}

[Source]

     # File lib/sequel/database/query.rb, line 102
102:     def indexes(table, opts={})
103:       raise NotImplemented, "#indexes should be overridden by adapters"
104:     end

Return a dataset modified by the query block

[Source]

    # File lib/sequel/extensions/query.rb, line 8
 8:     def query(&block)
 9:       dataset.query(&block)
10:     end

Runs the supplied SQL statement string on the database server. Returns nil. Options:

:server :The server to run the SQL on.
  DB.run("SET some_server_variable = 42")

[Source]

     # File lib/sequel/database/query.rb, line 111
111:     def run(sql, opts={})
112:       execute_ddl(sql, opts)
113:       nil
114:     end

Returns the schema for the given table as an array with all members being arrays of length 2, the first member being the column name, and the second member being a hash of column information. The table argument can also be a dataset, as long as it only has one table. Available options are:

:reload :Ignore any cached results, and get fresh information from the database.
:schema :An explicit schema to use. It may also be implicitly provided via the table name.

If schema parsing is supported by the database, the column information should hash at least contain the following entries:

:allow_null :Whether NULL is an allowed value for the column.
:db_type :The database type for the column, as a database specific string.
:default :The database default for the column, as a database specific string.
:primary_key :Whether the columns is a primary key column. If this column is not present, it means that primary key information is unavailable, not that the column is not a primary key.
:ruby_default :The database default for the column, as a ruby object. In many cases, complex database defaults cannot be parsed into ruby objects, in which case nil will be used as the value.
:type :A symbol specifying the type, such as :integer or :string.

Example:

  DB.schema(:artists)
  # [[:id,
  #   {:type=>:integer,
  #    :primary_key=>true,
  #    :default=>"nextval('artist_id_seq'::regclass)",
  #    :ruby_default=>nil,
  #    :db_type=>"integer",
  #    :allow_null=>false}],
  #  [:name,
  #   {:type=>:string,
  #    :primary_key=>false,
  #    :default=>nil,
  #    :ruby_default=>nil,
  #    :db_type=>"text",
  #    :allow_null=>false}]]

[Source]

     # File lib/sequel/database/query.rb, line 156
156:     def schema(table, opts={})
157:       raise(Error, 'schema parsing is not implemented on this database') unless respond_to?(:schema_parse_table, true)
158: 
159:       opts = opts.dup
160:       if table.is_a?(Dataset)
161:         o = table.opts
162:         from = o[:from]
163:         raise(Error, "can only parse the schema for a dataset with a single from table") unless from && from.length == 1 && !o.include?(:join) && !o.include?(:sql)
164:         tab = table.first_source_table
165:         sch, table_name = schema_and_table(tab)
166:         quoted_name = table.literal(tab)
167:         opts[:dataset] = table
168:       else
169:         sch, table_name = schema_and_table(table)
170:         quoted_name = quote_schema_table(table)
171:       end
172:       opts[:schema] = sch if sch && !opts.include?(:schema)
173: 
174:       @schemas.delete(quoted_name) if opts[:reload]
175:       return @schemas[quoted_name] if @schemas[quoted_name]
176: 
177:       cols = schema_parse_table(table_name, opts)
178:       raise(Error, 'schema parsing returned no columns, table probably doesn\'t exist') if cols.nil? || cols.empty?
179:       cols.each{|_,c| c[:ruby_default] = column_schema_to_ruby_default(c[:default], c[:type])}
180:       @schemas[quoted_name] = cols
181:     end

Returns true if a table with the given name exists. This requires a query to the database.

  DB.table_exists?(:foo) # => false
  # SELECT NULL FROM foo LIMIT 1

Note that since this does a SELECT from the table, it can give false negatives if you don‘t have permission to SELECT from the table.

[Source]

     # File lib/sequel/database/query.rb, line 191
191:     def table_exists?(name)
192:       sch, table_name = schema_and_table(name)
193:       name = SQL::QualifiedIdentifier.new(sch, table_name) if sch
194:       _table_exists?(from(name))
195:       true
196:     rescue DatabaseError
197:       false
198:     end

Return all tables in the database as an array of symbols.

  DB.tables # => [:albums, :artists]

[Source]

     # File lib/sequel/database/query.rb, line 203
203:     def tables(opts={})
204:       raise NotImplemented, "#tables should be overridden by adapters"
205:     end

Starts a database transaction. When a database transaction is used, either all statements are successful or none of the statements are successful. Note that MySQL MyISAM tabels do not support transactions.

The following options are respected:

:isolation :The transaction isolation level to use for this transaction, should be :uncommitted, :committed, :repeatable, or :serializable, used if given and the database/adapter supports customizable transaction isolation levels.
:prepare :A string to use as the transaction identifier for a prepared transaction (two-phase commit), if the database/adapter supports prepared transactions.
:rollback :Can the set to :reraise to reraise any Sequel::Rollback exceptions raised, or :always to always rollback even if no exceptions occur (useful for testing).
:server :The server to use for the transaction.
:savepoint :Whether to create a new savepoint for this transaction, only respected if the database/adapter supports savepoints. By default Sequel will reuse an existing transaction, so if you want to use a savepoint you must use this option.

[Source]

     # File lib/sequel/database/query.rb, line 228
228:     def transaction(opts={}, &block)
229:       synchronize(opts[:server]) do |conn|
230:         return yield(conn) if already_in_transaction?(conn, opts)
231:         _transaction(conn, opts, &block)
232:       end
233:     end

Return all views in the database as an array of symbols.

  DB.views # => [:gold_albums, :artists_with_many_albums]

[Source]

     # File lib/sequel/database/query.rb, line 238
238:     def views(opts={})
239:       raise NotImplemented, "#views should be overridden by adapters"
240:     end