module Sequel

Top level module for Sequel

There are some module methods that are added via metaprogramming, one for each supported adapter. For example:

DB = Sequel.sqlite # Memory database
DB = Sequel.sqlite('blog.db')
DB = Sequel.postgres('database_name',
       user:'user', 
       password: 'password',
       host: 'host'
       port: 5432, 
       max_connections: 10)

If a block is given to these methods, it is passed the opened Database object, which is closed (disconnected) when the block exits, just like a block passed to ::connect. For example:

Sequel.sqlite('blog.db'){|db| puts db[:users].count}

For a more expanded introduction, see the README. For a quicker introduction, see the cheat sheet.

The duplicate_columns_handler extension allows you to customize handling of duplicate column names in your queries on a per-database or per-dataset level.

For example, you may want to raise an exception if you join 2 tables together which contains a column that will override another columns.

To use the extension, you need to load the extension into the database:

DB.extension :duplicate_columns_handler

or into individual datasets:

ds = DB[:items].extension(:duplicate_columns_handler)

A database option is introduced: :on_duplicate_columns. It accepts a Symbol or any object that responds to :call.

on_duplicate_columns: :raise
on_duplicate_columns: :warn
on_duplicate_columns: :ignore
on_duplicate_columns: lambda{|columns| arbitrary_condition? ? :raise : :warn}

You may also configure duplicate columns handling for a specific dataset:

ds.on_duplicate_columns(:warn)
ds.on_duplicate_columns(:raise)
ds.on_duplicate_columns(:ignore)
ds.on_duplicate_columns{|columns| arbitrary_condition? ? :raise : :warn}
ds.on_duplicate_columns(lambda{|columns| arbitrary_condition? ? :raise : :warn})

If :raise is specified, a Sequel::DuplicateColumnError is raised. If :warn is specified, you will receive a warning via warn. If a callable is specified, it will be called. If no on_duplicate_columns is specified, the default is :warn.

Related module: Sequel::DuplicateColumnsHandler

The pg_range extension adds support for the PostgreSQL 9.2+ range types to Sequel. PostgreSQL range types are similar to ruby's Range class, representating an array of values. However, they are more flexible than ruby's ranges, allowing exclusive beginnings and endings (ruby's range only allows exclusive endings), and unbounded beginnings and endings (which ruby's range does not support).

This extension integrates with Sequel's native postgres and jdbc/postgresql adapters, so that when range type values are retrieved, they are parsed and returned as instances of Sequel::Postgres::PGRange. PGRange mostly acts like a Range, but it's not a Range as not all PostgreSQL range type values would be valid ruby ranges. If the range type value you are using is a valid ruby range, you can call PGRange#to_range to get a Range. However, if you call PGRange#to_range on a range type value uses features that ruby's Range does not support, an exception will be raised.

In addition to the parser, this extension comes with literalizers for both PGRange and Range that use the standard Sequel literalization callbacks, so they work on all adapters.

To turn an existing Range into a PGRange, use Sequel.pg_range:

Sequel.pg_range(range)

If you have loaded the core_extensions extension, or you have loaded the core_refinements extension and have activated refinements for the file, you can also use Range#pg_range:

range.pg_range

You may want to specify a specific range type:

Sequel.pg_range(range, :daterange)
range.pg_range(:daterange)

If you specify the range database type, Sequel will automatically cast the value to that type when literalizing.

To use this extension, load it into the Database instance:

DB.extension :pg_range

See the schema modification guide for details on using range type columns in CREATE/ALTER TABLE statements.

This extension makes it easy to add support for other range types. In general, you just need to make sure that the subtype is handled and has the appropriate converter installed. For user defined types, you can do this via:

DB.add_conversion_proc(subtype_oid){|string| }

Then you can call Sequel::Postgres::PGRange::DatabaseMethods#register_range_type to automatically set up a handler for the range type. So if you want to support the timerange type (assuming the time type is already supported):

DB.register_range_type('timerange')

This extension integrates with the pg_array extension. If you plan to use arrays of range types, load the pg_array extension before the pg_range extension:

DB.extension :pg_array, :pg_range

Related module: Sequel::Postgres::PGRange

The round_timestamps extension will automatically round timestamp values to the database's supported level of precision before literalizing them.

For example, if the database supports millisecond precision, and you give it a Time value with microsecond precision, it will round it appropriately:

Time.at(1405341161.917999982833862)
# default: 2014-07-14 14:32:41.917999
# with extension: 2014-07-14 14:32:41.918000

The round_timestamps extension correctly deals with databases that support millisecond or second precision. In addition to handling Time values, it also handles DateTime values and Sequel::SQLTime values (for the TIME type).

To round timestamps for a single dataset:

ds = ds.extension(:round_timestamps)

To round timestamps for all datasets on a single database:

DB.extension(:round_timestamps)

Related module: Sequel::Dataset::RoundTimestamps

Constants

ADAPTER_MAP

Hash of adapters that have been used. The key is the adapter scheme symbol, and the value is the Database subclass.

AdapterNotFound

Error raised when the adapter requested doesn't exist or can't be loaded.

CheckConstraintViolation

Error raised when Sequel determines a database check constraint has been violated.

ConstraintViolation

Generic error raised when Sequel determines a database constraint has been violated.

DATABASES

Array of all databases to which Sequel has connected. If you are developing an application that can connect to an arbitrary number of databases, delete the database objects from this (or use the :keep_reference Database option or a block when connecting) or they will not get garbage collected.

DEFAULT_INFLECTIONS_PROC

Proc that is instance_execed to create the default inflections for both the model inflector and the inflector extension.

DatabaseConnectionError

Error raised when the Sequel is unable to connect to the database with the connection parameters it was given.

DatabaseDisconnectError

Error raised by adapters when they determine that the connection to the database has been lost. Instructs the connection pool code to remove that connection from the pool so that other connections can be acquired automatically.

DatabaseError

Generic error raised by the database adapters, indicating a problem originating from the database server. Usually raised because incorrect SQL syntax is used.

DatabaseLockTimeout

Error raised when Sequel determines the database could not acquire a necessary lock before timing out. Use of Sequel::Dataset#nowait can often cause this exception when retrieving rows.

ForeignKeyConstraintViolation

Error raised when Sequel determines a database foreign key constraint has been violated.

InvalidOperation

Error raised on an invalid operation, such as trying to update or delete a joined or grouped dataset when the database does not support that.

InvalidValue

Error raised when attempting an invalid type conversion.

MAJOR

The major version of Sequel. Only bumped for major changes.

MINOR

The minor version of Sequel. Bumped for every non-patch level release, generally around once a month.

MassAssignmentRestriction

Raised when a mass assignment method is called in strict mode with either a restricted column or a column without a setter method.

NoExistingObject

Exception class raised when require_modification is set and an UPDATE or DELETE statement to modify the dataset doesn't modify a single row.

NotNullConstraintViolation

Error raised when Sequel determines a database NOT NULL constraint has been violated.

OPTS

Frozen hash used as the default options hash for most options.

PoolTimeout

Error raised when the connection pool cannot acquire a database connection before the timeout.

Rollback

Error that you should raise to signal a rollback of the current transaction. The transaction block will catch this exception, rollback the current transaction, and won't reraise it (unless a reraise is requested).

SHARED_ADAPTER_MAP

Hash of shared adapters that have been registered. The key is the adapter scheme symbol, and the value is the Sequel module containing the shared adapter.

SPLIT_SYMBOL_CACHE
SerializationFailure

Error raised when Sequel determines a serialization failure/deadlock in the database.

TINY

The tiny version of Sequel. Usually 0, only bumped for bugfix releases that fix regressions from previous versions.

UndefinedAssociation

Raised when an undefined association is used when eager loading.

UniqueConstraintViolation

Error raised when Sequel determines a database unique constraint has been violated.

VERSION

The version of Sequel you are using, as a string (e.g. “2.11.0”)

VERSION_NUMBER

The version of Sequel you are using, as a number (2.11.0 -> 20110)

VIRTUAL_ROW

Attributes

convert_two_digit_years[RW]

Sequel converts two digit years in Dates and DateTimes by default, so 01/02/03 is interpreted at January 2nd, 2003, and 12/13/99 is interpreted as December 13, 1999. You can override this to treat those dates as January 2nd, 0003 and December 13, 0099, respectively, by:

Sequel.convert_two_digit_years = false
datetime_class[RW]

Sequel can use either Time or DateTime for times returned from the database. It defaults to Time. To change it to DateTime:

Sequel.datetime_class = DateTime

Note that Time and DateTime objects have a different API, and in cases where they implement the same methods, they often implement them differently (e.g. + using seconds on Time and days on DateTime).

single_threaded[RW]

Set whether Sequel is being used in single threaded mode. by default, Sequel uses a thread-safe connection pool, which isn't as fast as the single threaded connection pool, and also has some additional thread safety checks. If your program will only have one thread, and speed is a priority, you should set this to true:

Sequel.single_threaded = true

Public Class Methods

condition_specifier?(obj) click to toggle source

Returns true if the passed object could be a specifier of conditions, false otherwise. Currently, Sequel considers hashes and arrays of two element arrays as condition specifiers.

Sequel.condition_specifier?({}) # => true
Sequel.condition_specifier?([[1, 2]]) # => true
Sequel.condition_specifier?([]) # => false
Sequel.condition_specifier?([1]) # => false
Sequel.condition_specifier?(1) # => false
# File lib/sequel/core.rb, line 71
def self.condition_specifier?(obj)
  case obj
  when Hash
    true
  when Array
    !obj.empty? && !obj.is_a?(SQL::ValueList) && obj.all?{|i| i.is_a?(Array) && (i.length == 2)}
  else
    false
  end
end
connect(*args, &block) click to toggle source

Creates a new database object based on the supplied connection string and optional arguments. The specified scheme determines the database class used, and the rest of the string specifies the connection options. For example:

DB = Sequel.connect('sqlite:/') # Memory database
DB = Sequel.connect('sqlite://blog.db') # ./blog.db
DB = Sequel.connect('sqlite:///blog.db') # /blog.db
DB = Sequel.connect('postgres://user:password@host:port/database_name')
DB = Sequel.connect('sqlite:///blog.db', max_connections: 10)

You can also pass a single options hash:

DB = Sequel.connect(adapter: 'sqlite', database: './blog.db')

If a block is given, it is passed the opened Database object, which is closed when the block exits. For example:

Sequel.connect('sqlite://blog.db'){|db| puts db[:users].count}

If a block is not given, a reference to this database will be held in Sequel::DATABASES until it is removed manually. This is by design, and used by Sequel::Model to pick the default database. It is recommended to pass a block if you do not want the resulting Database object to remain in memory until the process terminates, or use the keep_reference: false Database option.

For details, see the “Connecting to a Database” guide. To set up a master/slave or sharded database connection, see the “Master/Slave Databases and Sharding” guide.

# File lib/sequel/core.rb, line 114
def self.connect(*args, &block)
  Database.connect(*args, &block)
end
convert_exception_class(exception, klass) click to toggle source

Convert the exception to the given class. The given class should be Sequel::Error or a subclass. Returns an instance of klass with the message and backtrace of exception.

# File lib/sequel/core.rb, line 127
def self.convert_exception_class(exception, klass)
  return exception if exception.is_a?(klass)
  e = klass.new("#{exception.class}: #{exception.message}")
  e.wrapped_exception = exception
  e.set_backtrace(exception.backtrace)
  e
end
core_extensions?() click to toggle source

Assume the core extensions are not loaded by default, if the core_extensions extension is loaded, this will be overridden.

# File lib/sequel/core.rb, line 120
def self.core_extensions?
  false
end
elapsed_seconds_since(timer) click to toggle source

The elapsed seconds since the given timer object was created. The timer object should have been created via ::start_timer.

# File lib/sequel/core.rb, line 321
def self.elapsed_seconds_since(timer)
  start_timer - timer
end
extension(*extensions) click to toggle source

Load all Sequel extensions given. Extensions are just files that exist under sequel/extensions in the load path, and are just required.

In some cases, requiring an extension modifies classes directly, and in others, it just loads a module that you can extend other classes with. Consult the documentation for each extension you plan on using for usage.

Sequel.extension(:blank)
Sequel.extension(:core_extensions, :named_timezones)
# File lib/sequel/core.rb, line 143
def self.extension(*extensions)
  extensions.each{|e| Kernel.require "sequel/extensions/#{e}"}
end
inflections() { |Inflections| ... } click to toggle source

Yield the Inflections module if a block is given, and return the Inflections module.

# File lib/sequel/model/inflections.rb, line 5
def self.inflections
  yield Inflections if block_given?
  Inflections
end
json_parser_error_class() click to toggle source

The exception classed raised if there is an error parsing JSON. This can be overridden to use an alternative json implementation.

# File lib/sequel/core.rb, line 149
def self.json_parser_error_class
  JSON::ParserError
end
migration(&block) click to toggle source

The preferred method for writing Sequel migrations, using a DSL:

Sequel.migration do
  up do
    create_table(:artists) do
      primary_key :id
      String :name
    end
  end

  down do
    drop_table(:artists)
  end
end

Designed to be used with the Migrator class, part of the migration extension.

# File lib/sequel/extensions/migration.rb, line 287
def self.migration(&block)
  MigrationDSL.create(&block)
end
object_to_json(obj, *args, &block) click to toggle source

Convert given object to json and return the result. This can be overridden to use an alternative json implementation.

# File lib/sequel/core.rb, line 155
def self.object_to_json(obj, *args, &block)
  obj.to_json(*args, &block)
end
parse_json(json) click to toggle source

Parse the string as JSON and return the result. This can be overridden to use an alternative json implementation.

# File lib/sequel/core.rb, line 161
def self.parse_json(json)
  JSON.parse(json, :create_additions=>false)
end
recursive_map(array, converter) click to toggle source

Convert each item in the array to the correct type, handling multi-dimensional arrays. For each element in the array or subarrays, call the converter, unless the value is nil.

# File lib/sequel/core.rb, line 168
def self.recursive_map(array, converter)
  array.map do |i|
    if i.is_a?(Array)
      recursive_map(i, converter)
    elsif !i.nil?
      converter.call(i)
    end
  end
end
require(files, subdir=nil) click to toggle source

For backwards compatibility only. require_relative should be used instead.

# File lib/sequel/core.rb, line 179
def self.require(files, subdir=nil)
  # Use Kernel.require_relative to work around JRuby 9.0 bug
  Array(files).each{|f| Kernel.require_relative "#{"#{subdir}/" if subdir}#{f}"}
end
split_symbol(sym) click to toggle source

Splits the symbol into three parts, if symbol splitting is enabled (not the default). Each part will either be a string or nil. If symbol splitting is disabled, returns an array with the first and third parts being nil, and the second part beind a string version of the symbol.

For columns, these parts are the table, column, and alias. For tables, these parts are the schema, table, and alias.

# File lib/sequel/core.rb, line 193
def self.split_symbol(sym)
  unless v = Sequel.synchronize{SPLIT_SYMBOL_CACHE[sym]}
    if split_symbols?
      v = case s = sym.to_s
      when /\A((?:(?!__).)+)__((?:(?!___).)+)___(.+)\z/
        [$1.freeze, $2.freeze, $3.freeze].freeze
      when /\A((?:(?!___).)+)___(.+)\z/
        [nil, $1.freeze, $2.freeze].freeze
      when /\A((?:(?!__).)+)__(.+)\z/
        [$1.freeze, $2.freeze, nil].freeze
      else
        [nil, s.freeze, nil].freeze
      end
    else
      v = [nil,sym.to_s.freeze,nil].freeze
    end
    Sequel.synchronize{SPLIT_SYMBOL_CACHE[sym] = v}
  end
  v
end
split_symbols=(v) click to toggle source

Setting this to true enables Sequel's historical behavior of splitting symbols on double or triple underscores:

:table__column         # table.column
:column___alias        # column AS alias
:table__column___alias # table.column AS alias

It is only recommended to turn this on for backwards compatibility until such symbols have been converted to use newer Sequel APIs such as:

Sequel[:table][:column]            # table.column
Sequel[:column].as(:alias)         # column AS alias
Sequel[:table][:column].as(:alias) # table.column AS alias

Sequel::Database instances do their own caching of literalized symbols, and changing this setting does not affect those caches. It is recommended that if you want to change this setting, you do so directly after requiring Sequel, before creating any Sequel::Database instances.

Disabling symbol splitting will also disable the handling of double underscores in virtual row methods, causing such methods to yield regular identifers instead of qualified identifiers:

# Sequel.split_symbols = true
Sequel.expr{table__column}  # table.column
Sequel.expr{table[:column]} # table.column

# Sequel.split_symbols = false
Sequel.expr{table__column}  # table__column
Sequel.expr{table[:column]} # table.column
# File lib/sequel/core.rb, line 244
def self.split_symbols=(v)
  Sequel.synchronize{SPLIT_SYMBOL_CACHE.clear}
  @split_symbols = v
end
split_symbols?() click to toggle source

Whether Sequel currently splits symbols into qualified/aliased identifiers.

# File lib/sequel/core.rb, line 250
def self.split_symbols?
  @split_symbols
end
start_timer() click to toggle source

A timer object that can be passed to ::elapsed_seconds_since to return the number of seconds elapsed.

# File lib/sequel/core.rb, line 308
def self.start_timer
  Process.clock_gettime(Process::CLOCK_MONOTONIC)
end
string_to_date(string) click to toggle source

Converts the given string into a Date object.

Sequel.string_to_date('2010-09-10') # Date.civil(2010, 09, 10)
# File lib/sequel/core.rb, line 257
def self.string_to_date(string)
  begin
    Date.parse(string, Sequel.convert_two_digit_years)
  rescue => e
    raise convert_exception_class(e, InvalidValue)
  end
end
string_to_datetime(string) click to toggle source

Converts the given string into a Time or DateTime object, depending on the value of Sequel.datetime_class.

Sequel.string_to_datetime('2010-09-10 10:20:30') # Time.local(2010, 09, 10, 10, 20, 30)
# File lib/sequel/core.rb, line 269
def self.string_to_datetime(string)
  begin
    if datetime_class == DateTime
      DateTime.parse(string, convert_two_digit_years)
    else
      datetime_class.parse(string)
    end
  rescue => e
    raise convert_exception_class(e, InvalidValue)
  end
end
string_to_time(string) click to toggle source

Converts the given string into a Sequel::SQLTime object.

v = Sequel.string_to_time('10:20:30') # Sequel::SQLTime.parse('10:20:30')
DB.literal(v) # => '10:20:30'
# File lib/sequel/core.rb, line 285
def self.string_to_time(string)
  begin
    SQLTime.parse(string)
  rescue => e
    raise convert_exception_class(e, InvalidValue)
  end
end
synchronize() { |: synchronize(&block)| ... } click to toggle source

Unless in single threaded mode, protects access to any mutable global data structure in Sequel. Uses a non-reentrant mutex, so calling code should be careful. In general, this should only be used around the minimal possible code such as Hash#[], Hash#[]=, Hash#delete, Array#<<, and Array#delete.

# File lib/sequel/core.rb, line 301
def self.synchronize(&block)
  @single_threaded ? yield : @data_mutex.synchronize(&block)
end
transaction(dbs, opts=OPTS, &block) click to toggle source

Uses a transaction on all given databases with the given options. This:

Sequel.transaction([DB1, DB2, DB3]){}

is equivalent to:

DB1.transaction do
  DB2.transaction do
    DB3.transaction do
    end
  end
end

except that if Sequel::Rollback is raised by the block, the transaction is rolled back on all databases instead of just the last one.

Note that this method cannot guarantee that all databases will commit or rollback. For example, if DB3 commits but attempting to commit on DB2 fails (maybe because foreign key checks are deferred), there is no way to uncommit the changes on DB3. For that kind of support, you need to have two-phase commit/prepared transactions (which Sequel supports on some databases).

# File lib/sequel/core.rb, line 347
def self.transaction(dbs, opts=OPTS, &block)
  unless opts[:rollback]
    rescue_rollback = true
    opts = Hash[opts].merge!(:rollback=>:reraise)
  end
  pr = dbs.reverse.inject(block){|bl, db| proc{db.transaction(opts, &bl)}}
  if rescue_rollback
    begin
      pr.call
    rescue Sequel::Rollback
      nil
    end
  else
    pr.call
  end
end
version() click to toggle source

The version of Sequel you are using, as a string (e.g. “2.11.0”)

# File lib/sequel/version.rb, line 19
def self.version
  VERSION
end
virtual_row(&block) click to toggle source

If the supplied block takes a single argument, yield an SQL::VirtualRow instance to the block argument. Otherwise, evaluate the block in the context of a SQL::VirtualRow instance.

Sequel.virtual_row{a} # Sequel::SQL::Identifier.new(:a)
Sequel.virtual_row{|o| o.a} # Sequel::SQL::Function.new(:a)
# File lib/sequel/core.rb, line 371
def self.virtual_row(&block)
  vr = VIRTUAL_ROW
  case block.arity
  when -1, 0
    vr.instance_exec(&block)
  else
    block.call(vr)
  end  
end

Private Class Methods

adapter_method(adapter, *args, &block) click to toggle source

Helper method that the database adapter class methods that are added to Sequel via metaprogramming use to parse arguments.

# File lib/sequel/core.rb, line 385
def self.adapter_method(adapter, *args, &block)
  options = args.last.is_a?(Hash) ? args.pop : OPTS
  opts = {:adapter => adapter.to_sym}
  opts[:database] = args.shift if args.first.is_a?(String)
  if args.any?
    raise ::Sequel::Error, "Wrong format of arguments, either use (), (String), (Hash), or (String, Hash)"
  end

  connect(opts.merge(options), &block)
end