Class | Sequel::Database
In: | lib/sequel/adapters/do.rb lib/sequel/adapters/jdbc.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.

### Contents

- Methods that modify the database schema
- Methods relating to adapters, connecting, disconnecting, and sharding
- Methods that create datasets
- Methods that set defaults for created datasets
- Methods relating to logging
- Miscellaneous methods
- Methods that execute queries and/or return results

### Methods

<< [] adapter_class adapter_scheme add_column add_index add_servers alter_table call call_sproc cast_type_literal connect connect connect connect create_or_replace_view create_table create_table! create_table? create_view database_type dataset dataset dataset disconnect drop_column drop_index drop_table drop_view dump_indexes_migration dump_schema_migration dump_table_schema each_server execute execute execute execute_ddl execute_ddl execute_dui execute_dui execute_dui execute_insert execute_insert execute_insert fetch from get identifier_input_method identifier_input_method identifier_input_method= identifier_input_method= identifier_output_method identifier_output_method identifier_output_method= identifier_output_method= indexes indexes inspect jndi? literal log_info log_yield logger= new new new query quote_identifiers= quote_identifiers= quote_identifiers? remove_servers rename_column rename_table run schema select serial_primary_key_options servers set_column_default set_column_type single_threaded= single_threaded? subadapter supports_prepared_transactions? supports_savepoints? supports_transaction_isolation_levels? synchronize table_exists? tables tables test_connection transaction typecast_value uri uri uri url

### Included Modules

Metaprogramming

### Attributes

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

### Public Class methods

new(opts)

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 109
    109:       def initialize(opts)
    110:         super
    111:         @convert_types = typecast_value_boolean(@opts.fetch(:convert_types, true))
    112:         raise(Error, "No connection string specified") unless uri
    113:
    114:         resolved_uri = jndi? ? get_uri_from_jndi : uri
    115:
    116:         if match = /\Ajdbc:([^:]+)/.match(resolved_uri) and prok = DATABASE_SETUP[match[1].to_sym]
    117:           @driver = prok.call(self)
    118:         end
    119:       end

new(opts)

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 45
    45:       def initialize(opts)
    46:         super
    47:         raise(Error, "No connection string specified") unless uri
    48:         if prok = DATABASE_SETUP[subadapter.to_sym]
    49:           prok.call(self)
    50:         end
    51:       end

### Public Instance methods

call_sproc(name, opts = {}) {|log_yield(sql){cps.executeQuery}| ...}

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 123
    123:       def call_sproc(name, opts = {})
    124:         args = opts[:args] || []
    125:         sql = "{call #{name}(#{args.map{'?'}.join(',')})}"
    126:         synchronize(opts[:server]) do |conn|
    127:           cps = conn.prepareCall(sql)
    128:
    129:           i = 0
    130:           args.each{|arg| set_ps_arg(cps, arg, i+=1)}
    131:
    132:           begin
    133:             if block_given?
    134:               yield log_yield(sql){cps.executeQuery}
    135:             else
    136:               case opts[:type]
    137:               when :insert
    138:                 log_yield(sql){cps.executeUpdate}
    139:                 last_insert_id(conn, opts)
    140:               else
    141:                 log_yield(sql){cps.executeUpdate}
    142:               end
    143:             end
    144:           rescue NativeException, JavaSQL::SQLException => e
    145:             raise_error(e)
    146:           ensure
    147:             cps.close
    148:           end
    149:         end
    150:       end

connect(server)

Setup a DataObjects::Connection to the database.

[Source]

        # File lib/sequel/adapters/do.rb, line 54
    54:       def connect(server)
    55:         setup_connection(::DataObjects::Connection.new(uri(server_opts(server))))
    56:       end

connect(server)

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

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 153
    153:       def connect(server)
    154:         opts = server_opts(server)
    155:         conn = if jndi?
    156:           get_connection_from_jndi
    157:         else
    158:           args = [uri(opts)]
    159:           args.concat([opts[:user], opts[:password]]) if opts[:user] && opts[:password]
    160:           begin
    161:             JavaSQL::DriverManager.getConnection(*args)
    162:           rescue => e
    163:             raise e unless driver
    164:             # If the DriverManager can't get the connection - use the connect
    165:             # method of the driver. (This happens under Tomcat for instance)
    166:             props = java.util.Properties.new
    167:             if opts && opts[:user] && opts[:password]
    168:               props.setProperty("user", opts[:user])
    169:               props.setProperty("password", opts[:password])
    170:             end
    171:             driver.new.connect(args[0], props) rescue (raise e)
    172:           end
    173:         end
    174:         setup_connection(conn)
    175:       end

dataset(opts = nil)

Return instances of JDBC::Dataset with the given opts.

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 178
    178:       def dataset(opts = nil)
    179:         JDBC::Dataset.new(self, opts)
    180:       end

dataset(opts = nil)

Return a Sequel::DataObjects::Dataset object for this database.

[Source]

        # File lib/sequel/adapters/do.rb, line 59
    59:       def dataset(opts = nil)
    60:         DataObjects::Dataset.new(self, opts)
    61:       end

execute(sql, opts={}) {|log_yield(sql){stmt.executeQuery(sql)}| ...}

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 184
    184:       def execute(sql, opts={}, &block)
    185:         return call_sproc(sql, opts, &block) if opts[:sproc]
    186:         return execute_prepared_statement(sql, opts, &block) if [Symbol, Dataset].any?{|c| sql.is_a?(c)}
    187:         synchronize(opts[:server]) do |conn|
    188:           statement(conn) do |stmt|
    189:             if block_given?
    190:               yield log_yield(sql){stmt.executeQuery(sql)}
    191:             else
    192:               case opts[:type]
    193:               when :ddl
    194:                 log_yield(sql){stmt.execute(sql)}
    195:               when :insert
    196:                 log_yield(sql) do
    197:                   if requires_return_generated_keys?
    198:                     stmt.executeUpdate(sql, JavaSQL::Statement.RETURN_GENERATED_KEYS)
    199:                   else
    200:                     stmt.executeUpdate(sql)
    201:                   end
    202:                 end
    203:                 last_insert_id(conn, opts.merge(:stmt=>stmt))
    204:               else
    205:                 log_yield(sql){stmt.executeUpdate(sql)}
    206:               end
    207:             end
    208:           end
    209:         end
    210:       end

execute(sql, opts={}) {|res| ...}

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_ddl(sql, opts={})

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

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 215
    215:       def execute_ddl(sql, opts={})
    216:         execute(sql, {:type=>:ddl}.merge(opts))
    217:       end

execute_dui(sql, opts={})

Alias for execute

execute_dui(sql, opts={})

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_insert(sql, opts={})

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

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 221
    221:       def execute_insert(sql, opts={})
    222:         execute(sql, {:type=>:insert}.merge(opts))
    223:       end

execute_insert(sql, opts={})

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

indexes(table, opts={})

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

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 226
    226:       def indexes(table, opts={})
    227:         m = output_identifier_meth
    228:         im = input_identifier_meth
    229:         schema, table = schema_and_table(table)
    230:         schema ||= opts[:schema]
    231:         schema = im.call(schema) if schema
    232:         table = im.call(table)
    233:         indexes = {}
    234:         metadata(:getIndexInfo, nil, schema, table, false, true) do |r|
    235:           next unless name = r[:column_name]
    236:           next if respond_to?(:primary_key_index_re, true) and r[:index_name] =~ primary_key_index_re
    237:           i = indexes[m.call(r[:index_name])] ||= {:columns=>[], :unique=>[false, 0].include?(r[:non_unique])}
    238:           i[:columns] << m.call(name)
    239:         end
    240:         indexes
    241:       end

jndi?()

Whether or not JNDI is being used for this connection.

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 262
    262:       def jndi?
    263:         !!(uri =~ JNDI_URI_REGEXP)
    264:       end

subadapter()

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

tables(opts={})

All tables in this database

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 244
    244:       def tables(opts={})
    245:         ts = []
    246:         m = output_identifier_meth
    247:         metadata(:getTables, nil, nil, nil, ['TABLE'].to_java(:string)){|h| ts << m.call(h[:table_name])}
    248:         ts
    249:       end

uri(opts={})

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

uri(opts={})

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 255
    255:       def uri(opts={})
    256:         opts = @opts.merge(opts)
    257:         ur = opts[:uri] || opts[:url] || opts[:database]
    258:         ur =~ /^\Ajdbc:/ ? ur : "jdbc:#{ur}"
    259:       end

## 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

### Public Instance methods

add_column(table, *args)

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 30
    30:     def add_column(table, *args)
    31:       alter_table(table) {add_column(*args)}
    32:     end

add_index(table, columns, options={})

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 44
    44:     def add_index(table, columns, options={})
    45:       e = options[:ignore_errors]
    46:       begin
    47:         alter_table(table){add_index(columns, options)}
    48:       rescue DatabaseError
    49:         raise unless e
    50:       end
    51:     end

alter_table(name, generator=nil, &block)

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 70
    70:     def alter_table(name, generator=nil, &block)
    71:       generator ||= Schema::AlterTableGenerator.new(self, &block)
    72:       alter_table_sql_list(name, generator.operations).flatten.each {|sql| execute_ddl(sql)}
    73:       remove_cached_schema(name)
    74:       nil
    75:     end

create_or_replace_view(name, source)

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 115
    115:     def create_or_replace_view(name, source)
    116:       source = source.sql if source.is_a?(Dataset)
    117:       execute_ddl("CREATE OR REPLACE VIEW #{quote_schema_table(name)} AS #{source}")
    118:       remove_cached_schema(name)
    119:       nil
    120:     end

create_table(name, options={}, &block)

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 91
    91:     def create_table(name, options={}, &block)
    92:       remove_cached_schema(name)
    93:       options = {:generator=>options} if options.is_a?(Schema::Generator)
    94:       generator = options[:generator] || Schema::Generator.new(self, &block)
    95:       create_table_from_generator(name, generator, options)
    96:       create_table_indexes_from_generator(name, generator, options)
    97:       nil
    98:     end

create_table!(name, options={}, &block)

Forcibly creates a table, attempting to drop it unconditionally (and catching any errors), then creating it.

[Source]

         # File lib/sequel/database/schema_methods.rb, line 101
    101:     def create_table!(name, options={}, &block)
    102:       drop_table(name) rescue nil
    103:       create_table(name, options, &block)
    104:     end

create_table?(name, options={}, &block)

Creates the table unless the table already exists

[Source]

         # File lib/sequel/database/schema_methods.rb, line 107
    107:     def create_table?(name, options={}, &block)
    108:       create_table(name, options, &block) unless table_exists?(name)
    109:     end

create_view(name, source)

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 126
    126:     def create_view(name, source)
    127:       source = source.sql if source.is_a?(Dataset)
    128:       execute_ddl("CREATE VIEW #{quote_schema_table(name)} AS #{source}")
    129:     end

drop_column(table, *args)

Removes a column from the specified table:

      DB.drop_column :items, :category

See alter_table.

[Source]

         # File lib/sequel/database/schema_methods.rb, line 136
    136:     def drop_column(table, *args)
    137:       alter_table(table) {drop_column(*args)}
    138:     end

drop_index(table, columns, options={})

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 146
    146:     def drop_index(table, columns, options={})
    147:       alter_table(table){drop_index(columns, options)}
    148:     end

drop_table(*names)

Drops one or more tables corresponding to the given names:

      DB.drop_table(:posts, :comments)

[Source]

         # File lib/sequel/database/schema_methods.rb, line 153
    153:     def drop_table(*names)
    154:       names.each do |n|
    155:         execute_ddl(drop_table_sql(n))
    156:         remove_cached_schema(n)
    157:       end
    158:       nil
    159:     end

drop_view(*names)

Drops one or more views corresponding to the given names:

      DB.drop_view(:cheap_items)

[Source]

         # File lib/sequel/database/schema_methods.rb, line 164
    164:     def drop_view(*names)
    165:       names.each do |n|
    166:         execute_ddl("DROP VIEW #{quote_schema_table(n)}")
    167:         remove_cached_schema(n)
    168:       end
    169:       nil
    170:     end

rename_column(table, *args)

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 189
    189:     def rename_column(table, *args)
    190:       alter_table(table) {rename_column(*args)}
    191:     end

rename_table(name, new_name)

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 177
    177:     def rename_table(name, new_name)
    178:       execute_ddl(rename_table_sql(name, new_name))
    179:       remove_cached_schema(name)
    180:       nil
    181:     end

set_column_default(table, *args)

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 198
    198:     def set_column_default(table, *args)
    199:       alter_table(table) {set_column_default(*args)}
    200:     end

set_column_type(table, *args)

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 207
    207:     def set_column_type(table, *args)
    208:       alter_table(table) {set_column_type(*args)}
    209:     end

## 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 informix jdbc mysql odbc openbase oracle postgres sqlite'.collect{|x| x.to_sym} |  | Array of supported database adapters

### Attributes

pool | [R] | The connection pool for this database

### Public Class methods

adapter_class(scheme)

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:       scheme = scheme.to_s.gsub('-', '_').to_sym
    19:
    20:       unless klass = ADAPTER_MAP[scheme]
    21:         # attempt to load the adapter file
    22:         begin
    23:           Sequel.tsk_require "sequel/adapters/#{scheme}"
    24:         rescue LoadError => e
    25:           raise Sequel.convert_exception_class(e, AdapterNotFound)
    26:         end
    27:
    28:         # make sure we actually loaded the adapter
    29:         unless klass = ADAPTER_MAP[scheme]
    30:           raise AdapterNotFound, "Could not load #{scheme} adapter"
    31:         end
    32:       end
    33:       klass
    34:     end

adapter_scheme()

Returns the scheme for the Database class.

[Source]

        # File lib/sequel/database/connecting.rb, line 37
    37:     def self.adapter_scheme
    38:       @scheme
    39:     end

connect(conn_string, opts = {}) {|db| ...}

Connects to a database. See Sequel.connect.

[Source]

        # File lib/sequel/database/connecting.rb, line 42
    42:     def self.connect(conn_string, opts = {})
    43:       case conn_string
    44:       when String
    45:         if match = /\A(jdbc|do):/o.match(conn_string)
    46:           c = adapter_class(match[1].to_sym)
    47:           opts = {:uri=>conn_string}.merge(opts)
    48:         else
    49:           uri = URI.parse(conn_string)
    50:           scheme = uri.scheme
    51:           scheme = :dbi if scheme =~ /\Adbi-/
    52:           c = adapter_class(scheme)
    53:           uri_options = c.send(:uri_to_options, uri)
    54:           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?
    55:           uri_options.entries.each{|k,v| uri_options[k] = URI.unescape(v) if v.is_a?(String)}
    56:           opts = uri_options.merge(opts)
    57:         end
    58:       when Hash
    59:         opts = conn_string.merge(opts)
    60:         c = adapter_class(opts[:adapter] || opts['adapter'])
    61:       else
    62:         raise Error, "Sequel::Database.connect takes either a Hash or a String, given: #{conn_string.inspect}"
    63:       end
    64:       # process opts a bit
    65:       opts = opts.inject({}) do |m, kv| k, v = *kv
    66:         k = :user if k.to_s == 'username'
    67:         m[k.to_sym] = v
    68:         m
    69:       end
    70:       begin
    71:         db = c.new(opts)
    72:         db.test_connection if opts[:test] && db.send(:typecast_value_boolean, opts[:test])
    73:         result = yield(db) if block_given?
    74:       ensure
    75:         if block_given?
    76:           db.disconnect if db
    77:           ::Sequel::DATABASES.delete(db)
    78:         end
    79:       end
    80:       block_given? ? result : db
    81:     end

single_threaded=(value)

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

[Source]

        # File lib/sequel/database/connecting.rb, line 85
    85:     def self.single_threaded=(value)
    86:       @@single_threaded = value
    87:     end

### Public Instance methods

add_servers(servers)

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 119
    119:     def add_servers(servers)
    120:       @opts[:servers] = @opts[:servers] ? @opts[:servers].merge(servers) : servers
    121:       @pool.add_servers(servers.keys)
    122:     end

connect(server)

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

[Source]

         # File lib/sequel/database/connecting.rb, line 125
    125:     def connect(server)
    126:       raise NotImplemented, "#connect should be overridden by adapters"
    127:     end

database_type()

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).

[Source]

         # File lib/sequel/database/connecting.rb, line 136
    136:     def database_type
    137:       self.class.adapter_scheme
    138:     end

disconnect(opts = {})

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.

[Source]

         # File lib/sequel/database/connecting.rb, line 144
    144:     def disconnect(opts = {})
    145:       pool.disconnect(opts)
    146:     end

each_server(&block)

Yield a new database object 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 153
    153:     def each_server(&block)
    154:       servers.each{|s| self.class.connect(server_opts(s), &block)}
    155:     end

remove_servers(*servers)

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 167
    167:     def remove_servers(*servers)
    168:       if @opts[:servers] && !@opts[:servers].empty?
    169:         servs = @opts[:servers].dup
    170:         servers.flatten!
    171:         servers.each{|s| servs.delete(s)}
    172:         @opts[:servers] = servs
    173:         @pool.remove_servers(servers)
    174:       end
    175:     end

servers()

An array of servers/shards for this Database object.

[Source]

         # File lib/sequel/database/connecting.rb, line 178
    178:     def servers
    179:       pool.servers
    180:     end

single_threaded?()

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

[Source]

         # File lib/sequel/database/connecting.rb, line 183
    183:     def single_threaded?
    184:       @single_threaded
    185:     end

synchronize(server=nil, &block)

Acquires a database connection, yielding it to the passed block.

[Source]

         # File lib/sequel/database/connecting.rb, line 188
    188:     def synchronize(server=nil, &block)
    189:       @pool.hold(server || :default, &block)
    190:     end

test_connection(server=nil)

Attempts to acquire a database connection. Returns true if successful. Will probably raise an error if unsuccessful.

[Source]

         # File lib/sequel/database/connecting.rb, line 194
    194:     def test_connection(server=nil)
    195:       synchronize(server){|conn|}
    196:       true
    197:     end

## Methods that create datasets

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

### Public Instance methods

[](*args)

Returns a dataset from the database. If the first argument is a string, the method acts as an alias for Database#fetch, returning a dataset for arbitrary SQL:

      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 18
    18:     def [](*args)
    19:       (String === args.first) ? fetch(*args) : from(*args)
    20:     end

dataset()

Returns a blank dataset for this database

[Source]

        # File lib/sequel/database/dataset.rb, line 23
    23:     def dataset
    24:       ds = Sequel::Dataset.new(self)
    25:     end

fetch(sql, *args, &block)

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 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 40
    40:     def fetch(sql, *args, &block)
    41:       ds = dataset.with_sql(sql, *args)
    42:       ds.each(&block) if block
    43:       ds
    44:     end

from(*args, &block)

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

[Source]

        # File lib/sequel/database/dataset.rb, line 48
    48:     def from(*args, &block)
    49:       ds = dataset.from(*args)
    50:       block ? ds.filter(&block) : ds
    51:     end

select(*args, &block)

Returns a new dataset with the select method invoked.

[Source]

        # File lib/sequel/database/dataset.rb, line 54
    54:     def select(*args, &block)
    55:       dataset.select(*args, &block)
    56:     end

## Methods that set defaults for created datasets

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

### Attributes

default_schema | [RW] | The default schema to use, generally should be nil.

### Public Class methods

identifier_input_method()

The method to call on identifiers going into the database

[Source]

        # File lib/sequel/database/dataset_defaults.rb, line 18
    18:     def self.identifier_input_method
    19:       @@identifier_input_method
    20:     end

identifier_input_method=(v)

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 24
    24:     def self.identifier_input_method=(v)
    25:       @@identifier_input_method = v || ""
    26:     end

identifier_output_method()

The method to call on identifiers coming from the database

[Source]

        # File lib/sequel/database/dataset_defaults.rb, line 29
    29:     def self.identifier_output_method
    30:       @@identifier_output_method
    31:     end

identifier_output_method=(v)

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 35
    35:     def self.identifier_output_method=(v)
    36:       @@identifier_output_method = v || ""
    37:     end

quote_identifiers=(value)

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

[Source]

        # File lib/sequel/database/dataset_defaults.rb, line 41
    41:     def self.quote_identifiers=(value)
    42:       @@quote_identifiers = value
    43:     end

### Public Instance methods

identifier_input_method()

The method to call on identifiers going into the database

[Source]

        # File lib/sequel/database/dataset_defaults.rb, line 49
    49:     def identifier_input_method
    50:       case @identifier_input_method
    51:       when nil
    52:         @identifier_input_method = @opts.fetch(:identifier_input_method, (@@identifier_input_method.nil? ? identifier_input_method_default : @@identifier_input_method))
    53:         @identifier_input_method == "" ? nil : @identifier_input_method
    54:       when ""
    55:         nil
    56:       else
    57:         @identifier_input_method
    58:       end
    59:     end

identifier_input_method=(v)

Set the method to call on identifiers going into the database

[Source]

        # File lib/sequel/database/dataset_defaults.rb, line 62
    62:     def identifier_input_method=(v)
    63:       reset_schema_utility_dataset
    64:       @identifier_input_method = v || ""
    65:     end

identifier_output_method()

The method to call on identifiers coming from the database

[Source]

        # File lib/sequel/database/dataset_defaults.rb, line 68
    68:     def identifier_output_method
    69:       case @identifier_output_method
    70:       when nil
    71:         @identifier_output_method = @opts.fetch(:identifier_output_method, (@@identifier_output_method.nil? ? identifier_output_method_default : @@identifier_output_method))
    72:         @identifier_output_method == "" ? nil : @identifier_output_method
    73:       when ""
    74:         nil
    75:       else
    76:         @identifier_output_method
    77:       end
    78:     end

identifier_output_method=(v)

Set the method to call on identifiers coming from the database

[Source]

        # File lib/sequel/database/dataset_defaults.rb, line 81
    81:     def identifier_output_method=(v)
    82:       reset_schema_utility_dataset
    83:       @identifier_output_method = v || ""
    84:     end

quote_identifiers=(v)

Whether to quote identifiers (columns and tables) for this database

[Source]

        # File lib/sequel/database/dataset_defaults.rb, line 87
    87:     def quote_identifiers=(v)
    88:       reset_schema_utility_dataset
    89:       @quote_identifiers = v
    90:     end

quote_identifiers?()

Returns true if the database quotes identifiers.

[Source]

        # File lib/sequel/database/dataset_defaults.rb, line 93
    93:     def quote_identifiers?
    94:       return @quote_identifiers unless @quote_identifiers.nil?
    95:       @quote_identifiers = @opts.fetch(:quote_identifiers, (@@quote_identifiers.nil? ? quote_identifiers_default : @@quote_identifiers))
    96:     end

## 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

### Public Instance methods

log_info(message, args=nil)

Log a message at level info to all loggers.

[Source]

        # File lib/sequel/database/logging.rb, line 16
    16:     def log_info(message, args=nil)
    17:       log_each(:info, args ? "#{message}; #{args.inspect}" : message)
    18:     end

log_yield(sql, args=nil) {|if @loggers.empty?| ...}

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 22
    22:     def log_yield(sql, args=nil)
    23:       return yield if @loggers.empty?
    24:       sql = "#{sql}; #{args.inspect}" if args
    25:       start = Time.now
    26:       begin
    27:         yield
    28:       rescue => e
    29:         log_each(:error, "#{e.class}: #{e.message.strip}: #{sql}")
    30:         raise
    31:       ensure
    32:         log_duration(Time.now - start, sql) unless e
    33:       end
    34:     end

logger=(logger)

Remove any existing loggers and just use the given logger.

[Source]

        # File lib/sequel/database/logging.rb, line 37
    37:     def logger=(logger)
    38:       @loggers = Array(logger)
    39:     end

## Miscellaneous methods

These methods don‘t fit neatly into another category.

### Attributes

opts | [R] | The options for this database

### Public Class methods

new(opts = {}, &block)

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

Sequel::Database is an abstract class that is not useful by itself.

Takes 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
- :loggers : An array of loggers to use.
- :quote_identifiers : Whether to quote identifiers
- :single_threaded : Whether to use a single-threaded connection pool

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

[Source]

        # File lib/sequel/database/misc.rb, line 38
    38:     def initialize(opts = {}, &block)
    39:       @opts ||= opts
    40:       @opts = connection_pool_default_options.merge(@opts)
    41:       @loggers = Array(@opts[:logger]) + Array(@opts[:loggers])
    42:       self.log_warn_duration = @opts[:log_warn_duration]
    43:       @opts[:disconnection_proc] ||= proc{|conn| disconnect_connection(conn)}
    44:       block ||= proc{|server| connect(server)}
    45:       @opts[:servers] = {} if @opts[:servers].is_a?(String)
    46:
    47:       @opts[:single_threaded] = @single_threaded = typecast_value_boolean(@opts.fetch(:single_threaded, @@single_threaded))
    48:       @schemas = {}
    49:       @default_schema = @opts.fetch(:default_schema, default_schema_default)
    50:       @prepared_statements = {}
    51:       @transactions = []
    52:       @identifier_input_method = nil
    53:       @identifier_output_method = nil
    54:       @quote_identifiers = nil
    55:       @pool = ConnectionPool.get_pool(@opts, &block)
    56:
    57:       ::Sequel::DATABASES.push(self)
    58:     end

### Public Instance methods

cast_type_literal(type)

Cast the given type to a literal type

[Source]

        # File lib/sequel/database/misc.rb, line 61
    61:     def cast_type_literal(type)
    62:       type_literal(:type=>type)
    63:     end

inspect()

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 68
    68:     def inspect
    69:       "#<#{self.class}: #{(uri rescue opts).inspect}>"
    70:     end

literal(v)

Proxy the literal call to the dataset, used for default values.

[Source]

        # File lib/sequel/database/misc.rb, line 73
    73:     def literal(v)
    74:       schema_utility_dataset.literal(v)
    75:     end

serial_primary_key_options()

Default serial primary key options.

[Source]

        # File lib/sequel/database/misc.rb, line 78
    78:     def serial_primary_key_options
    79:       {:primary_key => true, :type => Integer, :auto_increment => true}
    80:     end

supports_prepared_transactions?()

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

[Source]

        # File lib/sequel/database/misc.rb, line 84
    84:     def supports_prepared_transactions?
    85:       false
    86:     end

supports_savepoints?()

Whether the database and adapter support savepoints, false by default

[Source]

        # File lib/sequel/database/misc.rb, line 89
    89:     def supports_savepoints?
    90:       false
    91:     end

supports_transaction_isolation_levels?()

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

[Source]

        # File lib/sequel/database/misc.rb, line 94
    94:     def supports_transaction_isolation_levels?
    95:       false
    96:     end

typecast_value(column_type, value)

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 103
    103:     def typecast_value(column_type, value)
    104:       return nil if value.nil?
    105:       meth = "typecast_value_#{column_type}"
    106:       begin
    107:         respond_to?(meth, true) ? send(meth, value) : value
    108:       rescue ArgumentError, TypeError => e
    109:         raise Sequel.convert_exception_class(e, InvalidValue)
    110:       end
    111:     end

uri()

Returns the URI identifying the database. This method can raise an error if the database used options instead of a connection string.

[Source]

         # File lib/sequel/database/misc.rb, line 116
    116:     def uri
    117:       uri = URI::Generic.new(
    118:         self.class.adapter_scheme.to_s,
    119:         nil,
    120:         @opts[:host],
    121:         @opts[:port],
    122:         nil,
    123:         "/#{@opts[:database]}",
    124:         nil,
    125:         nil,
    126:         nil
    127:       )
    128:       uri.user = @opts[:user]
    129:       uri.password = @opts[:password] if uri.user
    130:       uri.to_s
    131:     end

url()

Explicit alias of uri for easier subclassing.

[Source]

         # File lib/sequel/database/misc.rb, line 134
    134:     def url
    135:       uri
    136:     end

## 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 objects for this database, keyed by name
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

<<(sql)

Runs the supplied SQL statement string on the database server. Alias for run.

[Source]

        # File lib/sequel/database/query.rb, line 41
    41:     def <<(sql)
    42:       run(sql)
    43:     end

call(ps_name, hash={})

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

[Source]

        # File lib/sequel/database/query.rb, line 47
    47:     def call(ps_name, hash={})
    48:       prepared_statements[ps_name].call(hash)
    49:     end

dump_indexes_migration(options={})

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

dump_schema_migration(options={})

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

dump_table_schema(table, options={})

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

execute(sql, opts={})

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 53
    53:     def execute(sql, opts={})
    54:       raise NotImplemented, "#execute should be overridden by adapters"
    55:     end

execute_ddl(sql, opts={}, &block)

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

[Source]

        # File lib/sequel/database/query.rb, line 60
    60:     def execute_ddl(sql, opts={}, &block)
    61:       execute_dui(sql, opts, &block)
    62:     end

execute_dui(sql, opts={}, &block)

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 67
    67:     def execute_dui(sql, opts={}, &block)
    68:       execute(sql, opts, &block)
    69:     end

execute_insert(sql, opts={}, &block)

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 74
    74:     def execute_insert(sql, opts={}, &block)
    75:       execute_dui(sql, opts, &block)
    76:     end

get(*args, &block)

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

      # SELECT 1
      DB.get(1) #=> 1

      # SELECT version()
      DB.get(:version.sql_function) #=> ...

[Source]

        # File lib/sequel/database/query.rb, line 85
    85:     def get(*args, &block)
    86:       dataset.get(*args, &block)
    87:     end

indexes(table, opts={})

Return a hash containing index information. 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.

[Source]

        # File lib/sequel/database/query.rb, line 95
    95:     def indexes(table, opts={})
    96:       raise NotImplemented, "#indexes should be overridden by adapters"
    97:     end

query(&block)

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

run(sql, opts={})

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

- :server - The server to run the SQL on.

[Source]

         # File lib/sequel/database/query.rb, line 102
    102:     def run(sql, opts={})
    103:       execute_ddl(sql, opts)
    104:       nil
    105:     end

schema(table, opts={})

Parse the schema from the database. 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. Available options are:

- :reload - Get fresh information from the database, instead of using cached information. If table_name is blank, :reload should be used unless you are sure that schema has not been called before with a table_name, otherwise you may only getting the schemas for tables that have been requested explicitly.
- :schema - An explicit schema to use. It may also be implicitly provided via the table name.

[Source]

         # File lib/sequel/database/query.rb, line 119
    119:     def schema(table, opts={})
    120:       raise(Error, 'schema parsing is not implemented on this database') unless respond_to?(:schema_parse_table, true)
    121:
    122:       sch, table_name = schema_and_table(table)
    123:       quoted_name = quote_schema_table(table)
    124:       opts = opts.merge(:schema=>sch) if sch && !opts.include?(:schema)
    125:
    126:       @schemas.delete(quoted_name) if opts[:reload]
    127:       return @schemas[quoted_name] if @schemas[quoted_name]
    128:
    129:       cols = schema_parse_table(table_name, opts)
    130:       raise(Error, 'schema parsing returned no columns, table probably doesn\'t exist') if cols.nil? || cols.empty?
    131:       cols.each{|_,c| c[:ruby_default] = column_schema_to_ruby_default(c[:default], c[:type])}
    132:       @schemas[quoted_name] = cols
    133:     end

table_exists?(name)

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

[Source]

         # File lib/sequel/database/query.rb, line 137
    137:     def table_exists?(name)
    138:       begin
    139:         from(name).first
    140:         true
    141:       rescue
    142:         false
    143:       end
    144:     end

tables(opts={})

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

[Source]

         # File lib/sequel/database/query.rb, line 147
    147:     def tables(opts={})
    148:       raise NotImplemented, "#tables should be overridden by adapters"
    149:     end

transaction(opts={}) {|conn| ...}

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.
:prepare : | A string to use as the transaction identifier for a prepared transaction (two-phase commit), if the database/adapter supports prepared transactions
: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 167
    167:     def transaction(opts={}, &block)
    168:       synchronize(opts[:server]) do |conn|
    169:         return yield(conn) if already_in_transaction?(conn, opts)
    170:         _transaction(conn, opts, &block)
    171:       end
    172:     end

[Validate]