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Sequel

The thread_local_timezones extension allows you to set a per-thread timezone that will override the default global timezone while the thread is executing. The main use case is for web applications that execute each request in its own thread, and want to set the timezones based on the request. The most common example is having the database always store time in UTC, but have the application deal with the timezone of the current user. That can be done with:

Sequel.database_timezone = :utc
# In each thread:
Sequel.thread_application_timezone = current_user.timezone

This extension is designed to work with the named_timezones extension.

This extension adds the thread_application_timezone=, thread_database_timezone=, and thread_typecast_timezone= methods to the Sequel module. It overrides the application_timezone, database_timezone, and typecast_timezone methods to check the related thread local timezone first, and use it if present. If the related thread local timezone is not present, it falls back to the default global timezone.

There is one special case of note. If you have a default global timezone and you want to have a nil thread local timezone, you have to set the thread local value to :nil instead of nil:

Sequel.application_timezone = :utc
Sequel.thread_application_timezone = nil
Sequel.application_timezone # => :utc
Sequel.thread_application_timezone = :nil
Sequel.application_timezone # => nil

The sql_expr extension adds the sql_expr method to every object, which returns an object that works nicely with Sequel’s DSL. This is best shown by example:

1.sql_expr < :a     # 1 < a
false.sql_expr & :a # FALSE AND a
true.sql_expr | :a  # TRUE OR a
~nil.sql_expr       # NOT NULL
"a".sql_expr + "b"  # 'a' || 'b'

The pagination extension adds the Sequel::Dataset#paginate and each_page methods, which return paginated (limited and offset) datasets with some helpful methods that make creating a paginated display easier.


Adds the Sequel::Migration and Sequel::Migrator classes, which allow the user to easily group schema changes and migrate the database to a newer version or revert to a previous version.


The LooserTypecasting extension changes the float and integer typecasting to use the looser .to_f and .to_i instead of the more strict Kernel.Float and Kernel.Integer. To use it, you should extend the database with the Sequel::LooserTypecasting module after loading the extension:

Sequel.extension :looser_typecasting
DB.extend(Sequel::LooserTypecasting)

The schema_dumper extension supports dumping tables and indexes in a Sequel::Migration format, so they can be restored on another database (which can be the same type or a different type than the current database). The main interface is through Sequel::Database#dump_schema_migration.


The pretty_table extension adds Sequel::Dataset#print and the Sequel::PrettyTable class for creating nice-looking plain-text tables.


The query extension adds Sequel::Dataset#query which allows a different way to construct queries instead of the usual method chaining.


Top level module for Sequel

There are some class 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}

Sequel doesn't pay much attention to timezones by default, but you can set it handle timezones if you want. There are three separate timezone settings:

You can set also set all three timezones to the same value at once via Sequel.default_timezone=.

Sequel.application_timezone = :utc # or :local or nil
Sequel.database_timezone = :utc # or :local or nil
Sequel.typecast_timezone = :utc # or :local or nil
Sequel.default_timezone = :utc # or :local or nil

The only timezone values that are supported by default are :utc (convert to UTC), :local (convert to local time), and nil (don’t convert). If you need to convert to a specific timezone, or need the timezones being used to change based on the environment (e.g. current user), you need to use an extension (and use DateTime as the datetime_class).

You can set the SEQUEL_NO_CORE_EXTENSIONS constant or environment variable to have Sequel not extend the core classes.

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

Constants

ADAPTER_MAP

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

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 they will not get garbage collected.

DEFAULT_INFLECTIONS_PROC

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

LOCAL_DATETIME_OFFSET

The offset of the current time zone from UTC, as a fraction of a day.

LOCAL_DATETIME_OFFSET_SECS

The offset of the current time zone from UTC, in seconds.

MAJOR
MINOR
TINY
VERSION

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 setting this to 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, set this to DateTime.

virtual_row_instance_eval[RW]

Public Class Methods

Model(source) click to toggle source

Lets you create a Model subclass with its dataset already set. source can be an existing dataset or a symbol (in which case it will create a dataset using the default database with the given symbol as the table name).

The purpose of this method is to set the dataset automatically for a model class, if the table name doesn’t match the implicit name. This is neater than using set_dataset inside the class, doesn’t require a bogus query for the schema, and allows it to work correctly in a system that uses code reloading.

Example:

class Comment < Sequel::Model(:something)
  table_name # => :something
end
# File lib/sequel/model.rb, line 19
def self.Model(source)
  Model::ANONYMOUS_MODEL_CLASSES[source] ||= if source.is_a?(Database)
    c = Class.new(Model)
    c.db = source
    c
  else
    Class.new(Model).set_dataset(source)
  end
end
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 all two pairs as condition specifiers.

# File lib/sequel/core.rb, line 97
def self.condition_specifier?(obj)
  case obj
  when Hash
    true
  when Array
    !obj.empty? && obj.all?{|i| (Array === i) && (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)

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}

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 126
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 133
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
extension(*extensions) click to toggle source

Load all Sequel extensions given. Only loads extensions included in this release of Sequel, doesn’t load external extensions.

Sequel.extension(:schema_dumper)
Sequel.extension(:pagination, :query)
# File lib/sequel/core.rb, line 146
def self.extension(*extensions)
  extensions.each{|e| tsk_require "sequel/extensions/#{e}"}
end
identifier_input_method=(value) click to toggle source

Set the method to call on identifiers going into the database. This affects the literalization of identifiers by calling this method on them before they are input. Sequel upcases identifiers in all SQL strings for most databases, so to turn that off:

Sequel.identifier_input_method = nil

to downcase instead:

Sequel.identifier_input_method = :downcase

Other String instance methods work as well.

# File lib/sequel/core.rb, line 161
def self.identifier_input_method=(value)
  Database.identifier_input_method = value
end
identifier_output_method=(value) click to toggle source

Set the method to call on identifiers coming out of the database. This affects the literalization of identifiers by calling this method on them when they are retrieved from the database. Sequel downcases identifiers retrieved for most databases, so to turn that off:

Sequel.identifier_output_method = nil

to upcase instead:

Sequel.identifier_output_method = :upcase

Other String instance methods work as well.

# File lib/sequel/core.rb, line 177
def self.identifier_output_method=(value)
  Database.identifier_output_method = value
end
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 4
def self.inflections
  yield Inflections if block_given?
  Inflections
end
k_require(files, subdir=nil) click to toggle source

Alias to the standard version of require

Alias for: require
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 124
def self.migration(&block)
  MigrationDSL.create(&block)
end
quote_identifiers=(value) click to toggle source

Set whether to quote identifiers for all databases by default. By default, Sequel quotes identifiers in all SQL strings, so to turn that off:

Sequel.quote_identifiers = false
# File lib/sequel/core.rb, line 185
def self.quote_identifiers=(value)
  Database.quote_identifiers = value
end
require(files, subdir=nil) click to toggle source

Require all given files which should be in the same or a subdirectory of this file. If a subdir is given, assume all files are in that subdir.

# File lib/sequel/core.rb, line 191
def self.require(files, subdir=nil)
  Array(files).each{|f| super("#{File.dirname(__FILE__)}/#{"#{subdir}/" if subdir}#{f}")}
end
Also aliased as: k_require
single_threaded=(value) click to toggle source

Set whether to set the single threaded mode for all databases by default. By default, Sequel uses a threadsafe connection pool, which isn’t as fast as the single threaded connection pool. If your program will only have one thread, and speed is a priority, you may want to set this to true:

Sequel.single_threaded = true
# File lib/sequel/core.rb, line 201
def self.single_threaded=(value)
  Database.single_threaded = value
end
string_to_date(s) click to toggle source

Converts the given string into a Date object.

# File lib/sequel/core.rb, line 206
def self.string_to_date(s)
  begin
    Date.parse(s, Sequel.convert_two_digit_years)
  rescue => e
    raise convert_exception_class(e, InvalidValue)
  end
end
string_to_datetime(s) click to toggle source

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

# File lib/sequel/core.rb, line 216
def self.string_to_datetime(s)
  begin
    if datetime_class == DateTime
      DateTime.parse(s, convert_two_digit_years)
    else
      datetime_class.parse(s)
    end
  rescue => e
    raise convert_exception_class(e, InvalidValue)
  end
end
string_to_time(s) click to toggle source

Converts the given string into a Time object.

# File lib/sequel/core.rb, line 229
def self.string_to_time(s)
  begin
    Time.parse(s)
  rescue => e
    raise convert_exception_class(e, InvalidValue)
  end
end
ts_require(*args) click to toggle source

Same as Sequel.require, but wrapped in a mutex in order to be thread safe.

# File lib/sequel/core.rb, line 238
def self.ts_require(*args)
  check_requiring_thread{require(*args)}
end
tsk_require(*args) click to toggle source

Same as Kernel.require, but wrapped in a mutex in order to be thread safe.

# File lib/sequel/core.rb, line 243
def self.tsk_require(*args)
  check_requiring_thread{k_require(*args)}
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 9
def self.version
  VERSION
end
virtual_row(&block) click to toggle source

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

# File lib/sequel/core.rb, line 251
def self.virtual_row(&block)
  vr = SQL::VirtualRow.new
  case block.arity
  when -1, 0
    vr.instance_eval(&block)
  else
    block.call(vr)
  end  
end

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