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 Sequel.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

:nocov:

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 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.

Timezones

Backwards compatible alias

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

Public Class Methods

core_extensions?() click to toggle source

This extension loads the core extensions.

   # File lib/sequel/extensions/core_extensions.rb
11 def Sequel.core_extensions?
12   true
13 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
6 def self.inflections
7   yield Inflections if block_given?
8   Inflections
9 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
291 def self.migration(&block)
292   MigrationDSL.create(&block)
293 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
22 def self.version
23   VERSION
24 end