class Sequel::Database

  1. lib/sequel/database.rb
  2. lib/sequel/database/connecting.rb
  3. lib/sequel/database/dataset.rb
  4. lib/sequel/database/dataset_defaults.rb
  5. lib/sequel/database/features.rb
  6. lib/sequel/database/logging.rb
  7. lib/sequel/database/misc.rb
  8. lib/sequel/database/query.rb
  9. lib/sequel/database/schema_methods.rb
  10. lib/sequel/database/transactions.rb
  11. show all
Superclass: Object

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.


Public Class

  1. adapter_class
  2. adapter_scheme
  3. after_initialize
  4. connect
  5. extension
  6. load_adapter
  7. new
  8. register_extension
  9. run_after_initialize
  10. set_shared_adapter_scheme

Public Instance

  1. <<
  2. []
  3. adapter_scheme
  4. add_column
  5. add_index
  6. add_servers
  7. after_commit
  8. after_rollback
  9. alter_table
  10. alter_table_generator
  11. cache_schema
  12. call
  13. cast_type_literal
  14. create_join_table
  15. create_join_table!
  16. create_join_table?
  17. create_or_replace_view
  18. create_table
  19. create_table!
  20. create_table?
  21. create_table_generator
  22. create_view
  23. database_type
  24. dataset
  25. dataset_class
  26. dataset_class=
  27. default_string_column_size
  28. disconnect
  29. disconnect_connection
  30. drop_column
  31. drop_index
  32. drop_join_table
  33. drop_table
  34. drop_table?
  35. drop_view
  36. execute_ddl
  37. execute_dui
  38. execute_insert
  39. extend_datasets
  40. extension
  41. fetch
  42. freeze
  43. from
  44. from_application_timestamp
  45. get
  46. global_index_namespace?
  47. in_transaction?
  48. inspect
  49. literal
  50. literal_symbol
  51. literal_symbol_set
  52. log_connection_info
  53. log_connection_yield
  54. log_exception
  55. log_info
  56. log_warn_duration
  57. logger=
  58. loggers
  59. opts
  60. pool
  61. prepared_statement
  62. prepared_statements
  63. quote_identifier
  64. remove_servers
  65. rename_column
  66. rename_table
  67. rollback_checker
  68. rollback_on_exit
  69. run
  70. schema
  71. schema_type_class
  72. select
  73. serial_primary_key_options
  74. servers
  75. set_column_default
  76. set_column_type
  77. set_prepared_statement
  78. sharded?
  79. single_threaded?
  80. sql_log_level
  81. supports_create_table_if_not_exists?
  82. supports_deferrable_constraints?
  83. supports_deferrable_foreign_key_constraints?
  84. supports_drop_table_if_exists?
  85. supports_foreign_key_parsing?
  86. supports_index_parsing?
  87. supports_partial_indexes?
  88. supports_prepared_transactions?
  89. supports_savepoints?
  90. supports_savepoints_in_prepared_transactions?
  91. supports_schema_parsing?
  92. supports_table_listing?
  93. supports_transaction_isolation_levels?
  94. supports_transactional_ddl?
  95. supports_view_listing?
  96. supports_views_with_check_option?
  97. supports_views_with_local_check_option?
  98. synchronize
  99. table_exists?
  100. test_connection
  101. timezone
  102. timezone
  103. to_application_timestamp
  104. transaction
  105. transaction_isolation_level
  106. typecast_value
  107. uri
  108. url
  109. valid_connection?


OPTS = Sequel::OPTS  

1 - Methods that execute queries and/or return results


COLUMN_SCHEMA_DATETIME_TYPES = [:date, :datetime].freeze  
COLUMN_SCHEMA_STRING_TYPES = [:string, :blob, :date, :datetime, :time, :enum, :set, :interval].freeze  


cache_schema [RW]

Whether the schema should be cached for this database. True by default for performance, can be set to false to always issue a database query to get the schema.

prepared_statements [R]

The prepared statement object hash for this database, keyed by name symbol

Public Instance methods


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

DB << "UPDATE albums SET artist_id = NULL" << "DROP TABLE artists"
[show source]
   # File lib/sequel/database/query.rb
25 def <<(sql)
26   run(sql)
27   self
28 end
call(ps_name, hash=OPTS, &block)

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

DB[:items].where(id: 1).prepare(:first, :sa) # SELECT * FROM items WHERE id = 1
[show source]
   # File lib/sequel/database/query.rb
35 def call(ps_name, hash=OPTS, &block)
36   prepared_statement(ps_name).call(hash, &block)
37 end
execute_ddl(sql, opts=OPTS, &block)

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

[show source]
   # File lib/sequel/database/query.rb
42 def execute_ddl(sql, opts=OPTS, &block)
43   execute_dui(sql, opts, &block)
44 end
execute_dui(sql, opts=OPTS, &block)

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

[show source]
   # File lib/sequel/database/query.rb
49 def execute_dui(sql, opts=OPTS, &block)
50   execute(sql, opts, &block)
51 end
execute_insert(sql, opts=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.

[show source]
   # File lib/sequel/database/query.rb
56 def execute_insert(sql, opts=OPTS, &block)
57   execute_dui(sql, opts, &block)
58 end
get(*args, &block)

Returns a single value from the database, see Dataset#get.

DB.get(1) # SELECT 1
# => 1
DB.get{server_version.function} # SELECT server_version()
[show source]
   # File lib/sequel/database/query.rb
65 def get(*args, &block)
66   @default_dataset.get(*args, &block)
67 end
run(sql, opts=OPTS)

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


The server to run the SQL on."SET some_server_variable = 42")
[show source]
   # File lib/sequel/database/query.rb
74 def run(sql, opts=OPTS)
75   sql = literal(sql) if sql.is_a?(SQL::PlaceholderLiteralString)
76   execute_ddl(sql, opts)
77   nil
78 end
schema(table, opts=OPTS)

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


Ignore any cached results, and get fresh information from the database.


An explicit schema to use. It may also be implicitly provided via the table name.

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


Whether NULL is an allowed value for the column.


The database type for the column, as a database specific string.


The database default for the column, as a database specific string, or nil if there is no default value.


Whether the columns is a primary key column. If this column is not present, it means that primary key information is unavailable, not that the column is not a primary key.


The database default for the column, as a ruby object. In many cases, complex database defaults cannot be parsed into ruby objects, in which case nil will be used as the value.


A symbol specifying the type, such as :integer or :string.


# [[:id,
#   {:type=>:integer,
#    :primary_key=>true,
#    :default=>"nextval('artist_id_seq'::regclass)",
#    :ruby_default=>nil,
#    :db_type=>"integer",
#    :allow_null=>false}],
#  [:name,
#   {:type=>:string,
#    :primary_key=>false,
#    :default=>nil,
#    :ruby_default=>nil,
#    :db_type=>"text",
#    :allow_null=>false}]]
[show source]
    # File lib/sequel/database/query.rb
121 def schema(table, opts=OPTS)
122   raise(Error, 'schema parsing is not implemented on this database') unless supports_schema_parsing?
124   opts = opts.dup
125   tab = if table.is_a?(Dataset)
126     o = table.opts
127     from = o[:from]
128     raise(Error, "can only parse the schema for a dataset with a single from table") unless from && from.length == 1 && !o.include?(:join) && !o.include?(:sql)
129     table.first_source_table
130   else
131     table
132   end
134   qualifiers = split_qualifiers(tab)
135   table_name = qualifiers.pop
136   sch = qualifiers.pop
137   information_schema_schema = case qualifiers.length
138   when 1
139     Sequel.identifier(*qualifiers)
140   when 2
141     Sequel.qualify(*qualifiers)
142   end
144   if table.is_a?(Dataset)
145     quoted_name = table.literal(tab)
146     opts[:dataset] = table
147   else
148     quoted_name = schema_utility_dataset.literal(table)
149   end
151   opts[:schema] = sch if sch && !opts.include?(:schema)
152   opts[:information_schema_schema] = information_schema_schema if information_schema_schema && !opts.include?(:information_schema_schema)
154   Sequel.synchronize{@schemas.delete(quoted_name)} if opts[:reload]
155   if v = Sequel.synchronize{@schemas[quoted_name]}
156     return v
157   end
159   cols = schema_parse_table(table_name, opts)
160   raise(Error, "schema parsing returned no columns, table #{table_name.inspect} probably doesn't exist") if cols.nil? || cols.empty?
162   primary_keys = 0
163   auto_increment_set = false
164   cols.each do |_,c|
165     auto_increment_set = true if c.has_key?(:auto_increment)
166     primary_keys += 1 if c[:primary_key]
167   end
169   cols.each do |_,c|
170     c[:ruby_default] = column_schema_to_ruby_default(c[:default], c[:type]) unless c.has_key?(:ruby_default)
171     if c[:primary_key] && !auto_increment_set
172       # If adapter didn't set it, assume that integer primary keys are auto incrementing
173       c[:auto_increment] = primary_keys == 1 && !!(c[:db_type] =~ /int/io)
174     end
175     if !c[:max_length] && c[:type] == :string && (max_length = column_schema_max_length(c[:db_type]))
176       c[:max_length] = max_length
177     end
178   end
179   schema_post_process(cols)
181   Sequel.synchronize{@schemas[quoted_name] = cols} if cache_schema
182   cols
183 end

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

DB.table_exists?(:foo) # => false

Note that since this does a SELECT from the table, it can give false negatives if you don't have permission to SELECT from the table.

[show source]
    # File lib/sequel/database/query.rb
193 def table_exists?(name)
194   sch, table_name = schema_and_table(name)
195   name =, table_name) if sch
196   ds = from(name)
197   transaction(:savepoint=>:only){_table_exists?(ds)}
198   true
199 rescue DatabaseError
200   false
201 end

2 - Methods that modify the database schema


COLUMN_DEFINITION_ORDER = [:collate, :default, :null, :unique, :primary_key, :auto_increment, :references].freeze  

The order of column modifiers to use when defining a column.

COMBINABLE_ALTER_TABLE_OPS = [:add_column, :drop_column, :rename_column, :set_column_type, :set_column_default, :set_column_null, :add_constraint, :drop_constraint].freeze  

The alter table operations that are combinable.

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, String, unique: true, null: false
DB.add_column :items, :category, String, default: 'ruby'

See alter_table.

[show source]
   # File lib/sequel/database/schema_methods.rb
25 def add_column(table, *args)
26   alter_table(table) {add_column(*args)}
27 end
add_index(table, columns, options=OPTS)

Adds an index to a table for the given columns:

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



Ignore any DatabaseErrors that are raised


Name to use for index instead of default

See alter_table.

[show source]
   # File lib/sequel/database/schema_methods.rb
40 def add_index(table, columns, options=OPTS)
41   e = options[:ignore_errors]
42   begin
43     alter_table(table){add_index(columns, options)}
44   rescue DatabaseError
45     raise unless e
46   end
47   nil
48 end
alter_table(name, &block)

Alters the given table with the specified block. Example:

DB.alter_table :items do
  add_column :category, String, default: 'ruby'
  drop_column :category
  rename_column :cntr, :counter
  set_column_type :value, Float
  set_column_default :value, 4.2
  add_index [:group, :category]
  drop_index [:group, :category]

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 guide.

[show source]
   # File lib/sequel/database/schema_methods.rb
67 def alter_table(name, &block)
68   generator = alter_table_generator(&block)
69   remove_cached_schema(name)
70   apply_alter_table_generator(name, generator)
71   nil
72 end

Return a new Schema::AlterTableGenerator instance with the receiver as the database and the given block.

[show source]
   # File lib/sequel/database/schema_methods.rb
76 def alter_table_generator(&block)
77, &block)
78 end
create_join_table(hash, options=OPTS)

Create a join table using a hash of foreign keys to referenced table names. Example:

create_join_table(cat_id: :cats, dog_id: :dogs)
# CREATE TABLE cats_dogs (
#  cat_id integer NOT NULL REFERENCES cats,
#  dog_id integer NOT NULL REFERENCES dogs,
#  PRIMARY KEY (cat_id, dog_id)
# )
# CREATE INDEX cats_dogs_dog_id_cat_id_index ON cats_dogs(dog_id, cat_id)

The primary key and index are used so that almost all operations on the table can benefit from one of the two indexes, and the primary key ensures that entries in the table are unique, which is the typical desire for a join table.

The default table name this will create is the sorted version of the two hash values, joined by an underscore. So the following two method calls create the same table:

create_join_table(cat_id: :cats, dog_id: :dogs) # cats_dogs
create_join_table(dog_id: :dogs, cat_id: :cats) # cats_dogs

You can provide column options by making the values in the hash be option hashes, so long as the option hashes have a :table entry giving the table referenced:

create_join_table(cat_id: {table: :cats, type: :Bignum}, dog_id: :dogs)

You can provide a second argument which is a table options hash:

create_join_table({cat_id: :cats, dog_id: :dogs}, temp: true)

Some table options are handled specially:


The options to pass to the index


The name of the table to create


Set to true not to create the second index.


Set to true to not create the primary key.

[show source]
    # File lib/sequel/database/schema_methods.rb
119 def create_join_table(hash, options=OPTS)
120   keys = hash.keys.sort
121   create_table(join_table_name(hash, options), options) do
122     keys.each do |key|
123       v = hash[key]
124       unless v.is_a?(Hash)
125         v = {:table=>v}
126       end
127       v[:null] = false unless v.has_key?(:null)
128       foreign_key(key, v)
129     end
130     primary_key(keys) unless options[:no_primary_key]
131     index(keys.reverse, options[:index_options] || OPTS) unless options[:no_index]
132   end
133   nil
134 end
create_join_table!(hash, options=OPTS)

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

[show source]
    # File lib/sequel/database/schema_methods.rb
137 def create_join_table!(hash, options=OPTS)
138   drop_table?(join_table_name(hash, options))
139   create_join_table(hash, options)
140 end
create_join_table?(hash, options=OPTS)

Creates the join table unless it already exists.

[show source]
    # File lib/sequel/database/schema_methods.rb
143 def create_join_table?(hash, options=OPTS)
144   if supports_create_table_if_not_exists? && options[:no_index]
145     create_join_table(hash, options.merge(:if_not_exists=>true))
146   elsif !table_exists?(join_table_name(hash, options))
147     create_join_table(hash, options)
148   end
149 end
create_or_replace_view(name, source, options = OPTS)

Creates a view, replacing a view with the same name if one already exists.

DB.create_or_replace_view(:some_items, "SELECT * FROM items WHERE price < 100")
DB.create_or_replace_view(:some_items, DB[:items].where(category: 'ruby'))

For databases where replacing a view is not natively supported, support is emulated by dropping a view with the same name before creating the view.

[show source]
    # File lib/sequel/database/schema_methods.rb
239 def create_or_replace_view(name, source, options = OPTS)
240   if supports_create_or_replace_view?
241     options = options.merge(:replace=>true)
242   else
243     swallow_database_error{drop_view(name)}
244   end
246   create_view(name, source, options)
247   nil
248 end
create_table(name, options=OPTS, &block)

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

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

General options:


Create the table using the value, which should be either a dataset or a literal SQL string. If this option is used, a block should not be given to the method.


Ignore any errors when creating indexes.


Create the table as a temporary table.

MySQL specific options:


The character set to use for the table.


The collation to use for the table.


The table engine to use for the table.

PostgreSQL specific options:


Either :preserve_rows (default), :drop or :delete_rows. Should only be specified when creating a temporary table.


Create a foreign table. The value should be the name of the foreign server that was specified in CREATE SERVER.


Inherit from a different table. An array can be specified to inherit from multiple tables.


Create the table as an unlogged table.


The OPTIONS clause to use for foreign tables. Should be a hash where keys are option names and values are option values. Note that option names are unquoted, so you should not use untrusted keys.


The tablespace to use for the table.

See Schema::CreateTableGenerator and the “Schema Modification” guide.

[show source]
    # File lib/sequel/database/schema_methods.rb
187 def create_table(name, options=OPTS, &block)
188   remove_cached_schema(name)
189   if sql = options[:as]
190     raise(Error, "can't provide both :as option and block to create_table") if block
191     create_table_as(name, sql, options)
192   else
193     generator = options[:generator] || create_table_generator(&block)
194     create_table_from_generator(name, generator, options)
195     create_table_indexes_from_generator(name, generator, options)
196   end
197   nil
198 end
create_table!(name, options=OPTS, &block)

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

DB.create_table!(:a){Integer :a} 
# SELECT NULL FROM a LIMIT 1 -- check existence
# DROP TABLE a -- drop table if already exists
# CREATE TABLE a (a integer)
[show source]
    # File lib/sequel/database/schema_methods.rb
206 def create_table!(name, options=OPTS, &block)
207   drop_table?(name)
208   create_table(name, options, &block)
209 end
create_table?(name, options=OPTS, &block)

Creates the table unless the table already exists.

DB.create_table?(:a){Integer :a} 
# SELECT NULL FROM a LIMIT 1 -- check existence
# CREATE TABLE a (a integer) -- if it doesn't already exist
[show source]
    # File lib/sequel/database/schema_methods.rb
216 def create_table?(name, options=OPTS, &block)
217   options = options.dup
218   generator = options[:generator] ||= create_table_generator(&block)
219   if generator.indexes.empty? && supports_create_table_if_not_exists?
220     create_table(name, options.merge!(:if_not_exists=>true))
221   elsif !table_exists?(name)
222     create_table(name, options)
223   end
224 end

Return a new Schema::CreateTableGenerator instance with the receiver as the database and the given block.

[show source]
    # File lib/sequel/database/schema_methods.rb
228 def create_table_generator(&block)
229, &block)
230 end
create_view(name, source, options = OPTS)

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

DB.create_view(:cheap_items, "SELECT * FROM items WHERE price < 100")
# CREATE VIEW cheap_items AS
# SELECT * FROM items WHERE price < 100

DB.create_view(:ruby_items, DB[:items].where(category: 'ruby'))
# CREATE VIEW ruby_items AS
# SELECT * FROM items WHERE (category = 'ruby')

DB.create_view(:checked_items, DB[:items].where(:foo), check: true)
# CREATE VIEW checked_items AS
# SELECT * FROM items WHERE foo

DB.create_view(:bar_items, DB[:items].select(:foo), columns: [:bar])
# CREATE VIEW bar_items (bar) AS
# SELECT foo FROM items



The column names to use for the view. If not given, automatically determined based on the input dataset.


Adds a WITH CHECK OPTION clause, so that attempting to modify rows in the underlying table that would not be returned by the view is not allowed. This can be set to :local to use WITH LOCAL CHECK OPTION.

PostgreSQL/SQLite specific option:


Create a temporary view, automatically dropped on disconnect.

PostgreSQL specific options:


Creates a materialized view, similar to a regular view, but backed by a physical table.


Creates a recursive view. As columns must be specified for recursive views, you can also set them as the value of this option. Since a recursive view requires a union that isn't in a subquery, if you are providing a Dataset as the source argument, if should probably call the union method with the all: true and from_self: false options.


The tablespace to use for materialized views.

[show source]
    # File lib/sequel/database/schema_methods.rb
290 def create_view(name, source, options = OPTS)
291   execute_ddl(create_view_sql(name, source, options))
292   remove_cached_schema(name)
293   nil
294 end
drop_column(table, *args)

Removes a column from the specified table:

DB.drop_column :items, :category

See alter_table.

[show source]
    # File lib/sequel/database/schema_methods.rb
301 def drop_column(table, *args)
302   alter_table(table) {drop_column(*args)}
303 end
drop_index(table, columns, options=OPTS)

Removes an index for the given table and column(s):

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

See alter_table.

[show source]
    # File lib/sequel/database/schema_methods.rb
311 def drop_index(table, columns, options=OPTS)
312   alter_table(table){drop_index(columns, options)}
313 end
drop_join_table(hash, options=OPTS)

Drop the join table that would have been created with the same arguments to create_join_table:

drop_join_table(cat_id: :cats, dog_id: :dogs)
# DROP TABLE cats_dogs
[show source]
    # File lib/sequel/database/schema_methods.rb
320 def drop_join_table(hash, options=OPTS)
321   drop_table(join_table_name(hash, options), options)
322 end

Drops one or more tables corresponding to the given names:

DB.drop_table(:posts) # DROP TABLE posts
DB.drop_table(:posts, :comments)
DB.drop_table(:posts, :comments, cascade: true)
[show source]
    # File lib/sequel/database/schema_methods.rb
329 def drop_table(*names)
330   options = names.last.is_a?(Hash) ? names.pop : OPTS 
331   names.each do |n|
332     execute_ddl(drop_table_sql(n, options))
333     remove_cached_schema(n)
334   end
335   nil
336 end

Drops the table if it already exists. If it doesn't exist, does nothing.

# SELECT NULL FROM a LIMIT 1 -- check existence
# DROP TABLE a -- if it already exists
[show source]
    # File lib/sequel/database/schema_methods.rb
344 def drop_table?(*names)
345   options = names.last.is_a?(Hash) ? names.pop : OPTS
346   if supports_drop_table_if_exists?
347     options = options.merge(:if_exists=>true)
348     names.each do |name|
349       drop_table(name, options)
350     end
351   else
352     names.each do |name|
353       drop_table(name, options) if table_exists?(name)
354     end
355   end
356   nil
357 end

Drops one or more views corresponding to the given names:

DB.drop_view(:cheap_items, :pricey_items)
DB.drop_view(:cheap_items, :pricey_items, cascade: true)
DB.drop_view(:cheap_items, :pricey_items, if_exists: true)



Also drop objects depending on this view.


Do not raise an error if the view does not exist.

PostgreSQL specific options:


Drop a materialized view.

[show source]
    # File lib/sequel/database/schema_methods.rb
372 def drop_view(*names)
373   options = names.last.is_a?(Hash) ? names.pop : OPTS
374   names.each do |n|
375     execute_ddl(drop_view_sql(n, options))
376     remove_cached_schema(n)
377   end
378   nil
379 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.

[show source]
    # File lib/sequel/database/schema_methods.rb
398 def rename_column(table, *args)
399   alter_table(table) {rename_column(*args)}
400 end
rename_table(name, new_name)

Renames a table:

DB.tables #=> [:items]
DB.rename_table :items, :old_items
DB.tables #=> [:old_items]
[show source]
    # File lib/sequel/database/schema_methods.rb
386 def rename_table(name, new_name)
387   execute_ddl(rename_table_sql(name, new_name))
388   remove_cached_schema(name)
389   nil
390 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.

[show source]
    # File lib/sequel/database/schema_methods.rb
407 def set_column_default(table, *args)
408   alter_table(table) {set_column_default(*args)}
409 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.

[show source]
    # File lib/sequel/database/schema_methods.rb
416 def set_column_type(table, *args)
417   alter_table(table) {set_column_type(*args)}
418 end

3 - Methods that create datasets

Public Instance methods


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

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

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

DB[:items].sql #=> "SELECT * FROM items"
[show source]
   # File lib/sequel/database/dataset.rb
21 def [](*args)
22   args.first.is_a?(String) ? fetch(*args) : from(*args)
23 end

Returns a blank dataset for this database.

DB.dataset # SELECT *
DB.dataset.from(:items) # SELECT * FROM items
[show source]
   # File lib/sequel/database/dataset.rb
29 def dataset
31 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 fetch method returns a dataset instance:

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

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

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

See caveats listed in Dataset#with_sql regarding datasets using custom SQL and the methods that can be called on them.

[show source]
   # File lib/sequel/database/dataset.rb
49 def fetch(sql, *args, &block)
50   ds = @default_dataset.with_sql(sql, *args)
51   ds.each(&block) if block
52   ds
53 end
from(*args, &block)

Returns a new dataset with the from method invoked. If a block is given, it acts as a virtual row block

DB.from(:items) # SELECT * FROM items
DB.from{schema[:table]} # SELECT * FROM schema.table
[show source]
   # File lib/sequel/database/dataset.rb
60 def from(*args, &block)
61   if block
62     @default_dataset.from(*args, &block)
63   elsif args.length == 1 && (table = args[0]).is_a?(Symbol)
64     @default_dataset.send(:cached_dataset, :"_from_#{table}_ds"){@default_dataset.from(table)}
65   else
66     @default_dataset.from(*args)
67   end
68 end
select(*args, &block)

Returns a new dataset with the select method invoked. # SELECT 1{server_version.function} # SELECT server_version() # SELECT id FROM items
[show source]
   # File lib/sequel/database/dataset.rb
75 def select(*args, &block)
76*args, &block)
77 end

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


ADAPTERS = %w'ado amalgalite ibmdb jdbc mock mysql mysql2 odbc oracle postgres sqlanywhere sqlite tinytds'.map(&:to_sym)  

Array of supported database adapters


pool [R]

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

Public Class methods


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

[show source]
   # File lib/sequel/database/connecting.rb
16 def self.adapter_class(scheme)
17   scheme.is_a?(Class) ? scheme : load_adapter(scheme.to_sym)
18 end

Returns the scheme symbol for the Database class.

[show source]
   # File lib/sequel/database/connecting.rb
21 def self.adapter_scheme
22   @scheme
23 end
connect(conn_string, opts = OPTS)

Connects to a database. See Sequel.connect.

[show source]
   # File lib/sequel/database/connecting.rb
26 def self.connect(conn_string, opts = OPTS)
27   case conn_string
28   when String
29     if conn_string.start_with?('jdbc:')
30       c = adapter_class(:jdbc)
31       opts = opts.merge(:orig_opts=>opts.dup)
32       opts = {:uri=>conn_string}.merge!(opts)
33     else
34       uri = URI.parse(conn_string)
35       scheme = uri.scheme
36       c = adapter_class(scheme)
37       uri_options = c.send(:uri_to_options, uri)
38       uri.query.split('&').map{|s| s.split('=')}.each{|k,v| uri_options[k.to_sym] = v if k && !k.empty?} unless uri.query.to_s.strip.empty?
39       uri_options.to_a.each{|k,v| uri_options[k] = URI::DEFAULT_PARSER.unescape(v) if v.is_a?(String)}
40       opts = uri_options.merge(opts).merge!(:orig_opts=>opts.dup, :uri=>conn_string, :adapter=>scheme)
41     end
42   when Hash
43     opts = conn_string.merge(opts)
44     opts = opts.merge(:orig_opts=>opts.dup)
45     c = adapter_class(opts[:adapter_class] || opts[:adapter] || opts['adapter'])
46   else
47     raise Error, "Sequel::Database.connect takes either a Hash or a String, given: #{conn_string.inspect}"
48   end
50   opts = opts.inject({}) do |m, (k,v)|
51     k = :user if k.to_s == 'username'
52     m[k.to_sym] = v
53     m
54   end
56   begin
57     db =
58     if block_given?
59       return yield(db)
60     end
61   ensure
62     if block_given?
63       db.disconnect if db
64       Sequel.synchronize{::Sequel::DATABASES.delete(db)}
65     end
66   end
67   db
68 end
load_adapter(scheme, opts=OPTS)

Load the adapter from the file system. Raises Sequel::AdapterNotFound if the adapter cannot be loaded, or if the adapter isn't registered correctly after being loaded. Options:


The Hash in which to look for an already loaded adapter (defaults to ADAPTER_MAP).


The subdirectory of sequel/adapters to look in, only to be used for loading subadapters.

[show source]
    # File lib/sequel/database/connecting.rb
 76 def self.load_adapter(scheme, opts=OPTS)
 77   map = opts[:map] || ADAPTER_MAP
 78   if subdir = opts[:subdir]
 79     file = "#{subdir}/#{scheme}"
 80   else
 81     file = scheme
 82   end
 84   unless obj = Sequel.synchronize{map[scheme]}
 85     # attempt to load the adapter file
 86     begin
 87       require "sequel/adapters/#{file}"
 88     rescue LoadError => e
 89       # If subadapter file doesn't exist, just return,
 90       # using the main adapter class without database customizations.
 91       return if subdir
 92       raise Sequel.convert_exception_class(e, AdapterNotFound)
 93     end
 95     # make sure we actually loaded the adapter
 96     unless obj = Sequel.synchronize{map[scheme]}
 97       raise AdapterNotFound, "Could not load #{file} adapter: adapter class not registered in ADAPTER_MAP"
 98     end
 99   end
101   obj
102 end
set_shared_adapter_scheme(scheme, mod)

Sets the given module as the shared adapter module for the given scheme. Used to register shared adapters for use by the mock adapter. Example:

# in file sequel/adapters/shared/mydb.rb
module Sequel::MyDB
  Sequel::Database.set_shared_adapter_scheme :mydb, self

  def self.mock_adapter_setup(db)
    # ...

  module DatabaseMethods
    # ...

  module DatasetMethods
    # ...

would allow the mock adapter to return a Database instance that supports the MyDB syntax via:

[show source]
    # File lib/sequel/database/connecting.rb
146 def self.set_shared_adapter_scheme(scheme, mod)
147   Sequel.synchronize{SHARED_ADAPTER_MAP[scheme] = mod}
148 end

Public Instance methods


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

# => :jdbc
[show source]
    # File lib/sequel/database/connecting.rb
161 def adapter_scheme
162   self.class.adapter_scheme
163 end

Dynamically add new servers or modify server options at runtime. Also adds new servers to the connection pool. Only usable when using a sharded connection pool.

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"})
[show source]
    # File lib/sequel/database/connecting.rb
173 def add_servers(servers)
174   unless sharded?
175     raise Error, "cannot call Database#add_servers on a Database instance that does not use a sharded connection pool"
176   end
178   h = @opts[:servers]
179   Sequel.synchronize{h.merge!(servers)}
180   @pool.add_servers(servers.keys)
181 end

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

# => :postgres
[show source]
    # File lib/sequel/database/connecting.rb
192 def database_type
193   adapter_scheme
194 end
disconnect(opts = OPTS)

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


Should be a symbol specifing the server to disconnect from,

or an array of symbols to specify multiple servers.


DB.disconnect # All servers
DB.disconnect(server: :server1) # Single server
DB.disconnect(server: [:server1, :server2]) # Multiple servers
[show source]
    # File lib/sequel/database/connecting.rb
206 def disconnect(opts = OPTS)
207   pool.disconnect(opts)
208 end

Should only be called by the connection pool code to disconnect a connection. By default, calls the close method on the connection object, since most adapters use that, but should be overwritten on other adapters.

[show source]
    # File lib/sequel/database/connecting.rb
213 def disconnect_connection(conn)
214   conn.close
215 end

Dynamically remove existing servers from the connection pool. Only usable when using a sharded connection pool

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)
[show source]
    # File lib/sequel/database/connecting.rb
226 def remove_servers(*servers)
227   unless sharded?
228     raise Error, "cannot call Database#remove_servers on a Database instance that does not use a sharded connection pool"
229   end
231   h = @opts[:servers]
232   servers.flatten.each{|s| Sequel.synchronize{h.delete(s)}}
233   @pool.remove_servers(servers)
234 end

An array of servers/shards for this Database object.

DB.servers # Unsharded: => [:default]
DB.servers # Sharded:   => [:default, :server1, :server2]
[show source]
    # File lib/sequel/database/connecting.rb
240 def servers
241   pool.servers
242 end

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

[show source]
    # File lib/sequel/database/connecting.rb
245 def single_threaded?
246   @single_threaded
247 end


[show source]
    # File lib/sequel/database/connecting.rb
251 def synchronize(server=nil)
252   @pool.hold(server || :default){|conn| yield conn}
253 end

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

[show source]
    # File lib/sequel/database/connecting.rb
277 def test_connection(server=nil)
278   synchronize(server){|conn|}
279   true
280 end

Check whether the given connection is currently valid, by running a query against it. If the query fails, the connection should probably be removed from the connection pool.

[show source]
    # File lib/sequel/database/connecting.rb
286 def valid_connection?(conn)
287   sql = valid_connection_sql
288   begin
289     log_connection_execute(conn, sql)
290   rescue Sequel::DatabaseError, *database_error_classes
291     false
292   else
293     true
294   end
295 end

5 - Methods that set defaults for created datasets


dataset_class [R]

The class to use for creating datasets. Should respond to new with the Database argument as the first argument, and an optional options hash.

Public Instance methods


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

[show source]
   # File lib/sequel/database/dataset_defaults.rb
18 def dataset_class=(c)
19   unless @dataset_modules.empty?
20     c =
21     @dataset_modules.each{|m| c.send(:include, m)}
22   end
23   @dataset_class = c
24   reset_default_dataset
25 end
extend_datasets(mod=nil, &block)

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

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

If a block is given, a Dataset::DatasetModule instance is created, allowing for the easy creation of named dataset methods that will do caching.


# Introspect columns for all of DB's datasets

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

# Add some named dataset methods
DB.extend_datasets do
  order :by_id, :id
  select :with_id_and_name, :id, :name
  where :active, :active

# SELECT id, name FROM table WHERE active ORDER BY id
[show source]
   # File lib/sequel/database/dataset_defaults.rb
62 def extend_datasets(mod=nil, &block)
63   raise(Error, "must provide either mod or block, not both") if mod && block
64   mod = if block
65   if @dataset_modules.empty?
66    @dataset_modules = [mod]
67    @dataset_class =
68   else
69    @dataset_modules << mod
70   end
71   @dataset_class.send(:include, mod)
72   reset_default_dataset
73 end

6 - Methods relating to logging


log_connection_info [RW]

Whether to include information about the connection in use when logging queries.

log_warn_duration [RW]

Numeric specifying the duration beyond which queries are logged at warn level instead of info level.

loggers [RW]

Array of SQL loggers to use for this database.

sql_log_level [RW]

Log level at which to log SQL queries. This is actually the method sent to the logger, so it should be the method name symbol. The default is :info, it can be set to :debug to log at DEBUG level.

Public Instance methods

log_connection_yield(sql, conn, args=nil)

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.

[show source]
   # File lib/sequel/database/logging.rb
37 def log_connection_yield(sql, conn, args=nil)
38   return yield if skip_logging?
39   sql = "#{connection_info(conn) if conn && log_connection_info}#{sql}#{"; #{args.inspect}" if args}"
40   timer = Sequel.start_timer
42   begin
43     yield
44   rescue => e
45     log_exception(e, sql)
46     raise
47   ensure
48     log_duration(Sequel.elapsed_seconds_since(timer), sql) unless e
49   end
50 end
log_exception(exception, message)

Log a message at error level, with information about the exception.

[show source]
   # File lib/sequel/database/logging.rb
26 def log_exception(exception, message)
27   log_each(:error, "#{exception.class}: #{exception.message.strip if exception.message}: #{message}")
28 end
log_info(message, args=nil)

Log a message at level info to all loggers.

[show source]
   # File lib/sequel/database/logging.rb
31 def log_info(message, args=nil)
32   log_each(:info, args ? "#{message}; #{args.inspect}" : message)
33 end

Remove any existing loggers and just use the given logger:

DB.logger =$stdout)
[show source]
   # File lib/sequel/database/logging.rb
55 def logger=(logger)
56   @loggers = Array(logger)
57 end

7 - Miscellaneous methods


CHECK_CONSTRAINT_SQLSTATES = %w'23513 23514'.freeze.each(&:freeze)  

Empty exception regexp to class map, used by default if Sequel doesn't have specific support for the database in use.


The general default size for string columns for all Sequel::Database instances.


Hash of extension name symbols to callable objects to load the extension into the Database object (usually by extending it with a module defined in the extension).

FOREIGN_KEY_CONSTRAINT_SQLSTATES = %w'23503 23506 23504'.freeze.each(&:freeze)  
NOT_NULL_CONSTRAINT_SQLSTATES = %w'23502'.freeze.each(&:freeze)  
SCHEMA_TYPE_CLASSES = {:string=>String, :integer=>Integer, :date=>Date, :datetime=>[Time, DateTime].freeze, :time=>Sequel::SQLTime, :boolean=>[TrueClass, FalseClass].freeze, :float=>Float, :decimal=>BigDecimal, :blob=>Sequel::SQL::Blob}.freeze  

Mapping of schema type symbols to class or arrays of classes for that symbol.

SERIALIZATION_CONSTRAINT_SQLSTATES = %w'40001'.freeze.each(&:freeze)  
UNIQUE_CONSTRAINT_SQLSTATES = %w'23505'.freeze.each(&:freeze)  


default_string_column_size [RW]

The specific default size of string columns for this Sequel::Database, usually 255 by default.

opts [R]

The options hash for this database

timezone [W]

Set the timezone to use for this database, overridding Sequel.database_timezone.

Public Class methods


Register a hook that will be run when a new Database is instantiated. It is called with the new database handle.

[show source]
   # File lib/sequel/database/misc.rb
34 def self.after_initialize(&block)
35   raise Error, "must provide block to after_initialize" unless block
36   Sequel.synchronize do
37     previous = @initialize_hook
38     @initialize_hook = proc do |db|
41     end
42   end
43 end

Apply an extension to all Database objects created in the future.

[show source]
   # File lib/sequel/database/misc.rb
46 def self.extension(*extensions)
47   after_initialize{|db| db.extension(*extensions)}
48 end
new(opts = OPTS)

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

Accepts the following options:


Whether schema should be cached for this Database instance


The default size of string columns, 255 by default.


Extensions to load into this Database instance. Can be a symbol, array of symbols, or string with extensions separated by columns. These extensions are loaded after connections are made by the :preconnect option.


Whether to keep a reference to this instance in Sequel::DATABASES, true by default.


A specific logger to use.


An array of loggers to use.


Whether connection information should be logged when logging queries.


The number of elapsed seconds after which queries should be logged at warn level.


A name to use for the Database object, displayed in PoolTimeout .


Automatically create the maximum number of connections, so that they don't need to be created as needed. This is useful when connecting takes a long time and you want to avoid possible latency during runtime. Set to :concurrently to create the connections in separate threads. Otherwise they'll be created sequentially.


Similar to the :extensions option, but loads the extensions before the connections are made by the :preconnect option.


Whether to quote identifiers.


A hash specifying a server/shard specific options, keyed by shard symbol .


Whether to use a single-threaded connection pool.


Method to use to log SQL to a logger, :info by default.

All options given are also passed to the connection pool. Additional options respected by the connection pool are :after_connect, :connect_sqls, :max_connections, :pool_timeout, :servers, and :servers_hash. See the connection pool documentation for details.

[show source]
    # File lib/sequel/database/misc.rb
124 def initialize(opts = OPTS)
125   @opts ||= opts
126   @opts = connection_pool_default_options.merge(@opts)
127   @loggers = Array(@opts[:logger]) + Array(@opts[:loggers])
128   @opts[:servers] = {} if @opts[:servers].is_a?(String)
129   @sharded = !!@opts[:servers]
130   @opts[:adapter_class] = self.class
131   @opts[:single_threaded] = @single_threaded = typecast_value_boolean(@opts.fetch(:single_threaded, Sequel.single_threaded))
132   @default_string_column_size = @opts[:default_string_column_size] || DEFAULT_STRING_COLUMN_SIZE
134   @schemas = {}
135   @prepared_statements = {}
136   @transactions = {}
137   @symbol_literal_cache = {}
139   @timezone = nil
141   @dataset_class = dataset_class_default
142   @cache_schema = typecast_value_boolean(@opts.fetch(:cache_schema, true))
143   @dataset_modules = []
144   @loaded_extensions = []
145   @schema_type_classes = SCHEMA_TYPE_CLASSES.dup
147   self.sql_log_level = @opts[:sql_log_level] ? @opts[:sql_log_level].to_sym : :info
148   self.log_warn_duration = @opts[:log_warn_duration]
149   self.log_connection_info = typecast_value_boolean(@opts[:log_connection_info])
151   @pool = ConnectionPool.get_pool(self, @opts)
153   reset_default_dataset
154   adapter_initialize
156   keep_reference = typecast_value_boolean(@opts[:keep_reference]) != false
157   begin
158     Sequel.synchronize{::Sequel::DATABASES.push(self)} if keep_reference
159     Sequel::Database.run_after_initialize(self)
161     initialize_load_extensions(:preconnect_extensions)
163     if typecast_value_boolean(@opts[:preconnect]) && @pool.respond_to?(:preconnect, true)
164       concurrent = typecast_value_string(@opts[:preconnect]) == "concurrently"
165       @pool.send(:preconnect, concurrent)
166     end
168     initialize_load_extensions(:extensions)
169     test_connection if typecast_value_boolean(@opts.fetch(:test, true)) && respond_to?(:connect, true)
170   rescue
171     Sequel.synchronize{::Sequel::DATABASES.delete(self)} if keep_reference
172     raise
173   end
174 end
register_extension(ext, mod=nil, &block)

Register an extension callback for Database objects. ext should be the extension name symbol, and mod should either be a Module that the database is extended with, or a callable object called with the database object. If mod is not provided, a block can be provided and is treated as the mod object.

[show source]
   # File lib/sequel/database/misc.rb
55 def self.register_extension(ext, mod=nil, &block)
56   if mod
57     raise(Error, "cannot provide both mod and block to Database.register_extension") if block
58     if mod.is_a?(Module)
59       block = proc{|db| db.extend(mod)}
60     else
61       block = mod
62     end
63   end
64   Sequel.synchronize{EXTENSIONS[ext] = block}
65 end

Run the after_initialize hook for the given instance.

[show source]
   # File lib/sequel/database/misc.rb
68 def self.run_after_initialize(instance)
70 end

Public Instance methods


Cast the given type to a literal type

DB.cast_type_literal(Float) # double precision
DB.cast_type_literal(:foo)  # foo
[show source]
    # File lib/sequel/database/misc.rb
203 def cast_type_literal(type)
204   type_literal(:type=>type)
205 end

Load an extension into the receiver. In addition to requiring the extension file, this also modifies the database to work with the extension (usually extending it with a module defined in the extension file). If no related extension file exists or the extension does not have specific support for Database objects, an Error will be raised. Returns self.

[show source]
    # File lib/sequel/database/misc.rb
212 def extension(*exts)
213   Sequel.extension(*exts)
214   exts.each do |ext|
215     if pr = Sequel.synchronize{EXTENSIONS[ext]}
216       if Sequel.synchronize{@loaded_extensions.include?(ext) ? false : (@loaded_extensions << ext)}
218       end
219     else
220       raise(Error, "Extension #{ext} does not have specific support handling individual databases (try: Sequel.extension #{ext.inspect})")
221     end
222   end
223   self
224 end

Freeze internal data structures for the Database instance.

[show source]
    # File lib/sequel/database/misc.rb
177 def freeze
178   valid_connection_sql
179   metadata_dataset
180   @opts.freeze
181   @loggers.freeze
182   @pool.freeze
183   @dataset_class.freeze
184   @dataset_modules.freeze
185   @schema_type_classes.freeze
186   @loaded_extensions.freeze
187   metadata_dataset
188   super
189 end

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

[show source]
    # File lib/sequel/database/misc.rb
229 def from_application_timestamp(v)
230   Sequel.convert_output_timestamp(v, timezone)
231 end

Returns a string representation of the database object including the class name and connection URI and options used when connecting (if any).

[show source]
    # File lib/sequel/database/misc.rb
235 def inspect
236   a = []
237   a << uri.inspect if uri
238   if (oo = opts[:orig_opts]) && !oo.empty?
239     a << oo.inspect
240   end
241   "#<#{self.class}: #{a.join(' ')}>"
242 end

Proxy the literal call to the dataset.

DB.literal(1)   # 1
DB.literal(:a)  # a
DB.literal('a') # 'a'
[show source]
    # File lib/sequel/database/misc.rb
249 def literal(v)
250   schema_utility_dataset.literal(v)
251 end

Return the literalized version of the symbol if cached, or nil if it is not cached.

[show source]
    # File lib/sequel/database/misc.rb
255 def literal_symbol(sym)
256   Sequel.synchronize{@symbol_literal_cache[sym]}
257 end
literal_symbol_set(sym, lit)

Set the cached value of the literal symbol.

[show source]
    # File lib/sequel/database/misc.rb
260 def literal_symbol_set(sym, lit)
261   Sequel.synchronize{@symbol_literal_cache[sym] = lit}
262 end

Synchronize access to the prepared statements cache.

[show source]
    # File lib/sequel/database/misc.rb
265 def prepared_statement(name)
266   Sequel.synchronize{prepared_statements[name]}
267 end

Proxy the quote_identifier method to the dataset, useful for quoting unqualified identifiers for use outside of datasets.

[show source]
    # File lib/sequel/database/misc.rb
272 def quote_identifier(v)
273   schema_utility_dataset.quote_identifier(v)
274 end

Return ruby class or array of classes for the given type symbol.

[show source]
    # File lib/sequel/database/misc.rb
277 def schema_type_class(type)
278   @schema_type_classes[type]
279 end

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

[show source]
    # File lib/sequel/database/misc.rb
282 def serial_primary_key_options
283   {:primary_key => true, :type => Integer, :auto_increment => true}
284 end
set_prepared_statement(name, ps)

Cache the prepared statement object at the given name.

[show source]
    # File lib/sequel/database/misc.rb
287 def set_prepared_statement(name, ps)
288   Sequel.synchronize{prepared_statements[name] = ps}
289 end

Whether this database instance uses multiple servers, either for sharding or for primary/replica configurations.

[show source]
    # File lib/sequel/database/misc.rb
293 def sharded?
294   @sharded
295 end

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

[show source]
    # File lib/sequel/database/misc.rb
298 def timezone
299   @timezone || Sequel.database_timezone
300 end

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

[show source]
    # File lib/sequel/database/misc.rb
305 def to_application_timestamp(v)
306   Sequel.convert_timestamp(v, timezone)
307 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.

[show source]
    # File lib/sequel/database/misc.rb
314 def typecast_value(column_type, value)
315   return nil if value.nil?
316   meth = "typecast_value_#{column_type}"
317   begin
318     # Allow calling private methods as per-type typecasting methods are private
319     respond_to?(meth, true) ? send(meth, value) : value
320   rescue ArgumentError, TypeError => e
321     raise Sequel.convert_exception_class(e, InvalidValue)
322   end
323 end

Returns the URI use to connect to the database. If a URI was not used when connecting, returns nil.

[show source]
    # File lib/sequel/database/misc.rb
327 def uri
328   opts[:uri]
329 end

Explicit alias of uri for easier subclassing.

[show source]
    # File lib/sequel/database/misc.rb
332 def url
333   uri
334 end

8 - Methods related to database transactions


TRANSACTION_ISOLATION_LEVELS = {:uncommitted=>'READ UNCOMMITTED'.freeze, :committed=>'READ COMMITTED'.freeze, :repeatable=>'REPEATABLE READ'.freeze, :serializable=>'SERIALIZABLE'.freeze}.freeze  


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

after_commit(opts=OPTS, &block)

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


If currently inside a savepoint, only run this hook on transaction commit if all enclosing savepoints have been released.


The server/shard to use.

[show source]
   # File lib/sequel/database/transactions.rb
31 def after_commit(opts=OPTS, &block)
32   raise Error, "must provide block to after_commit" unless block
33   synchronize(opts[:server]) do |conn|
34     if h = _trans(conn)
35       raise Error, "cannot call after_commit in a prepared transaction" if h[:prepare]
36       if opts[:savepoint] && in_savepoint?(conn)
37         add_savepoint_hook(conn, :after_commit, block)
38       else
39         add_transaction_hook(conn, :after_commit, block)
40       end
41     else
42       yield
43     end
44   end
45 end
after_rollback(opts=OPTS, &block)

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


If currently inside a savepoint, run this hook immediately when any enclosing savepoint is rolled back, which may be before the transaction commits or rollsback.


The server/shard to use.

[show source]
   # File lib/sequel/database/transactions.rb
55 def after_rollback(opts=OPTS, &block)
56   raise Error, "must provide block to after_rollback" unless block
57   synchronize(opts[:server]) do |conn|
58     if h = _trans(conn)
59       raise Error, "cannot call after_rollback in a prepared transaction" if h[:prepare]
60       if opts[:savepoint] && in_savepoint?(conn)
61         add_savepoint_hook(conn, :after_rollback, block)
62       else
63         add_transaction_hook(conn, :after_rollback, block)
64       end
65     end
66   end
67 end

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

[show source]
    # File lib/sequel/database/transactions.rb
113 def in_transaction?(opts=OPTS)
114   synchronize(opts[:server]){|conn| !!_trans(conn)}
115 end

Returns a proc that you can call to check if the transaction has been rolled back. The proc will return nil if the transaction is still in progress, true if the transaction was rolled back, and false if it was committed. Raises an Error if called outside a transaction. Respects the :server option for selecting a shard.

[show source]
    # File lib/sequel/database/transactions.rb
123 def rollback_checker(opts=OPTS)
124   synchronize(opts[:server]) do |conn|
125     raise Error, "not in a transaction" unless t = _trans(conn)
126     t[:rollback_checker] ||= proc{Sequel.synchronize{t[:rolled_back]}}
127   end
128 end

When exiting the transaction block through methods other than an exception (e.g. normal exit, non-local return, or throw), set the current transaction to rollback instead of committing. This is designed for use in cases where you want to preform a non-local return but also want to rollback instead of committing. Options:


Cancel the current rollback_on_exit setting, so exiting will commit instead of rolling back.


Rollback only the current savepoint if inside a savepoint. Can also be an positive integer value to rollback that number of enclosing savepoints, up to and including the transaction itself. If the database does not support savepoints, this option is ignored and the entire transaction is affected.


The server/shard the transaction is being executed on.

[show source]
    # File lib/sequel/database/transactions.rb
 83 def rollback_on_exit(opts=OPTS)
 84   synchronize(opts[:server]) do |conn|
 85     raise Error, "Cannot call Sequel:: Database#rollback_on_exit unless inside a transaction" unless h = _trans(conn)
 86     rollback = !opts[:cancel]
 88     if supports_savepoints?
 89       savepoints = h[:savepoints]
 91       if level = opts[:savepoint]
 92         level = 1 if level == true
 93         raise Error, "invalid :savepoint option to Database#rollback_on_exit: #{level.inspect}" unless level.is_a?(Integer)
 94         raise Error, "cannot pass nonpositive integer (#{level.inspect}) as :savepoint option to Database#rollback_on_exit" if level < 1
 95         level.times do |i|
 96           break unless savepoint = savepoints[-1 - i]
 97           savepoint[:rollback_on_exit] = rollback
 98         end
 99       else
100         savepoints[0][:rollback_on_exit] = rollback
101       end
102     else
103       h[:rollback_on_exit] = rollback
104     end
105   end
107   nil
108 end
transaction(opts=OPTS, &block)

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 tables do not support transactions.

The following general options are respected:


Automatically use a savepoint for Database#transaction calls inside this transaction block.


The transaction isolation level to use for this transaction, should be :uncommitted, :committed, :repeatable, or :serializable, used if given and the database/adapter supports customizable transaction isolation levels.


The number of times to retry if the :retry_on option is used. The default is 5 times. Can be set to nil to retry indefinitely, but that is not recommended.


Proc to execute before retrying if the :retry_on option is used. Called with two arguments: the number of retry attempts (counting the current one) and the error the last attempt failed with.


A string to use as the transaction identifier for a prepared transaction (two-phase commit), if the database/adapter supports prepared transactions.


An exception class or array of exception classes for which to automatically retry the transaction. Can only be set if not inside an existing transaction. Note that this should not be used unless the entire transaction block is idempotent, as otherwise it can cause non-idempotent behavior to execute multiple times.


Can be set to :reraise to reraise any Sequel::Rollback exceptions raised, or :always to always rollback even if no exceptions occur (useful for testing).


The server to use for the transaction. Set to :default, :read_only, or whatever symbol you used in the connect string when naming your servers.


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. If the surrounding transaction uses :auto_savepoint, you can set this to false to not use a savepoint. If the value given for this option is :only, it will only create a savepoint if it is inside a transaction.

PostgreSQL specific options:


(9.1+) If present, set to DEFERRABLE if true or NOT DEFERRABLE if false.


If present, set to READ ONLY if true or READ WRITE if false.


if non-nil, set synchronous_commit appropriately. Valid values true, :on, false, :off, :local (9.1+), and :remote_write (9.2+).

[show source]
    # File lib/sequel/database/transactions.rb
177 def transaction(opts=OPTS, &block)
178   opts = Hash[opts]
179   if retry_on = opts[:retry_on]
180     tot_retries = opts.fetch(:num_retries, 5)
181     num_retries = 0
182     begin
183       opts[:retry_on] = nil
184       opts[:retrying] = true
185       transaction(opts, &block)
186     rescue *retry_on => e
187       num_retries += 1
188       if tot_retries.nil? || num_retries <= tot_retries
189         opts[:before_retry].call(num_retries, e) if opts[:before_retry]
190         retry
191       end
192       raise
193     end
194   else
195     synchronize(opts[:server]) do |conn|
196       if opts[:savepoint] == :only
197         if supports_savepoints?
198           if _trans(conn)
199             opts[:savepoint] = true
200           else
201             return yield(conn)
202           end
203         else
204           opts[:savepoint] = false
205         end
206       end
208       if opts[:savepoint] && !supports_savepoints?
209         raise Sequel::InvalidOperation, "savepoints not supported on #{database_type}"
210       end
212       if already_in_transaction?(conn, opts)
213         if opts[:rollback] == :always && !opts.has_key?(:savepoint)
214           if supports_savepoints? 
215             opts[:savepoint] = true
216           else
217             raise Sequel::Error, "cannot set :rollback=>:always transaction option if already inside a transaction"
218           end
219         end
221         if opts[:savepoint] != false && (stack = _trans(conn)[:savepoints]) && stack.last[:auto_savepoint]
222           opts[:savepoint] = true
223         end
225         unless opts[:savepoint]
226           if opts[:retrying]
227             raise Sequel::Error, "cannot set :retry_on options if you are already inside a transaction"
228           end
229           return yield(conn)
230         end
231       end
233       _transaction(conn, opts, &block)
234     end
235   end
236 end

9 - Methods that describe what the database supports

Public Instance methods


Whether the database uses a global namespace for the index, true by default. If false, the indexes are going to be namespaced per table.

[show source]
   # File lib/sequel/database/features.rb
13 def global_index_namespace?
14   true
15 end

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

[show source]
   # File lib/sequel/database/features.rb
19 def supports_create_table_if_not_exists?
20   false
21 end

Whether the database supports deferrable constraints, false by default as few databases do.

[show source]
   # File lib/sequel/database/features.rb
25 def supports_deferrable_constraints?
26   false
27 end

Whether the database supports deferrable foreign key constraints, false by default as few databases do.

[show source]
   # File lib/sequel/database/features.rb
31 def supports_deferrable_foreign_key_constraints?
32   supports_deferrable_constraints?
33 end

Whether the database supports DROP TABLE IF EXISTS syntax, false by default.

[show source]
   # File lib/sequel/database/features.rb
37 def supports_drop_table_if_exists?
38   supports_create_table_if_not_exists?
39 end

Whether the database supports Database#foreign_key_list for parsing foreign keys.

[show source]
   # File lib/sequel/database/features.rb
43 def supports_foreign_key_parsing?
44   respond_to?(:foreign_key_list)
45 end

Whether the database supports Database#indexes for parsing indexes.

[show source]
   # File lib/sequel/database/features.rb
48 def supports_index_parsing?
49   respond_to?(:indexes)
50 end

Whether the database supports partial indexes (indexes on a subset of a table), false by default.

[show source]
   # File lib/sequel/database/features.rb
54 def supports_partial_indexes?
55   false
56 end

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

[show source]
   # File lib/sequel/database/features.rb
60 def supports_prepared_transactions?
61   false
62 end

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

[show source]
   # File lib/sequel/database/features.rb
65 def supports_savepoints?
66   false
67 end

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

[show source]
   # File lib/sequel/database/features.rb
71 def supports_savepoints_in_prepared_transactions?
72   supports_prepared_transactions? && supports_savepoints?
73 end

Whether the database supports schema parsing via Database#schema.

[show source]
   # File lib/sequel/database/features.rb
76 def supports_schema_parsing?
77   respond_to?(:schema_parse_table, true)
78 end

Whether the database supports Database#tables for getting list of tables.

[show source]
   # File lib/sequel/database/features.rb
81 def supports_table_listing?
82   respond_to?(:tables)
83 end

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

[show source]
   # File lib/sequel/database/features.rb
91 def supports_transaction_isolation_levels?
92   false
93 end

Whether DDL statements work correctly in transactions, false by default.

[show source]
   # File lib/sequel/database/features.rb
96 def supports_transactional_ddl?
97   false
98 end

Whether the database supports Database#views for getting list of views.

[show source]
   # File lib/sequel/database/features.rb
86 def supports_view_listing?
87   respond_to?(:views)
88 end

Whether CREATE VIEW … WITH CHECK OPTION is supported, false by default.

[show source]
    # File lib/sequel/database/features.rb
101 def supports_views_with_check_option?
102   !!view_with_check_option_support
103 end

Whether CREATE VIEW … WITH LOCAL CHECK OPTION is supported, false by default.

[show source]
    # File lib/sequel/database/features.rb
106 def supports_views_with_local_check_option?
107   view_with_check_option_support == :local
108 end