Class: ROM::SQL::Relation

Inherits:
Relation
  • Object
show all
Extended by:
Notifications::Listener
Includes:
ROM::SQL, Reading, Writing
Defined in:
lib/rom/sql/relation.rb,
lib/rom/sql/relation/reading.rb,
lib/rom/sql/relation/writing.rb

Overview

Sequel-specific relation extensions

Defined Under Namespace

Modules: Reading, Writing

Instance Method Summary collapse

Instance Method Details

#as_hash(attribute = primary_key) ⇒ Hash Originally defined in module Reading

Returns hash with all tuples being the key of each the provided attribute

Examples:

default use primary_key

users.as_hash
# {1 => {id: 1, name: 'Jane'}}

using other attribute

users.as_hash(:name)
# {'Jane' => {id: 1, name: 'Jane'}}

Returns:

  • (Hash)

#assoc(name) ⇒ Relation

Return relation that will load associated tuples of this relation

This method is useful for defining custom relation views for relation composition when you want to enhance default association query

Examples:

assoc(:tasks).where(tasks[:title] => "Task One")

Parameters:

  • name (Symbol) —

    The association name

Returns:



117
118
119
 
# File 'lib/rom/sql/relation.rb', line 117

def assoc(name)
  associations[name].()
end

#avg(*args) ⇒ Object Originally defined in module Reading

Returns a result of SQL AVG clause.

Examples:

users.avg(:age)

Parameters:

  • args (Array<Symbol>) —

    A list with column names

Returns:

  • Number

#count ⇒ Relation Originally defined in module Reading

Return relation count

Examples:

users.count
# => 12

Returns:

#delete(*args, &block) ⇒ Integer Originally defined in module Writing

Delete tuples from the relation

Examples:

users.delete # deletes all
users.where(name: 'Jane').delete # delete tuples
                                   from restricted relation

Returns:

  • (Integer) —

    Number of deleted tuples

#distinct(*columns) ⇒ Relation #distinct(&block) ⇒ Relation Originally defined in module Reading

Returns a copy of the relation with a SQL DISTINCT clause.

Overloads:

  • #distinct(*columns) ⇒ Relation

    Create a distinct statement from column names

    Examples:

    users.distinct(:country)

    Parameters:

    • columns (Array<Symbol>) —

      A list with column names

  • #distinct(&block) ⇒ Relation

    Create a distinct statement from a block

    Examples:

    users.distinct { func(id) }
# SELECT DISTINCT ON (count("id")) "id" ...

Returns:

#each_batch(size: 1000) {|| ... } ⇒ Object Originally defined in module Reading

Process the dataset in batches. The method yields a relation restricted by a primary key value. This means it discards any order internally and uses the PK sort. Currently, works only with a single-column primary key.

Examples:

update in batches

users.each_batch do |rel|
  rel.
    command(:update).
    call(name: users[:first_name].concat(users[:last_name])
end

Parameters:

  • [Integer] (Hash) —

    a customizable set of options

Yield Parameters:

#exclude(*args, &block) ⇒ Relation Originally defined in module Reading

Restrict a relation to not match criteria

Examples:

users.exclude(name: 'Jane')

Parameters:

  • args (Hash) —

    A hash with conditions for exclusion

Returns:

#exist?(*args, &block) ⇒ TrueClass, FalseClass Originally defined in module Reading

Checks whether a relation has at least one tuple

@example users.where(name: 'John').exist? # => true

users.exist?(name: 'Klaus') # => false

users.exist? { name.is('klaus') } # => false

@param [Array] args Optional restrictions to filter the relation @yield An optional block filters the relation using where DSL

Returns:

  • (TrueClass, FalseClass)

#exists(other, condition = nil) ⇒ SQL::Relation Originally defined in module Reading

Restrict with rows from another relation. Accepts only SQL relations and uses the EXISTS clause under the hood

Examples:

using associations

users.exists(tasks)

using provided condition

users.exists(tasks, tasks[:user_id] => users[:id])

Parameters:

  • other (SQL::Relation) —

    The other relation

  • condition (Hash, Object) (defaults to: nil) —

    An optional join condition

Returns:

#fetch(pk) ⇒ Relation Originally defined in module Reading

Fetch a tuple identified by the pk

Examples:

users.fetch(1)
# {:id => 1, name: "Jane"}

Returns:

Raises:

  • (ROM::TupleCountMismatchError) —

    When 0 or more than 1 tuples were found

#first ⇒ Hash Originally defined in module Reading

Get first tuple from the relation

Examples:

users.first
# {:id => 1, :name => "Jane"}

Returns:

  • (Hash)

#group(*columns) ⇒ Relation #group(*attributes) ⇒ Relation #group(*attributes, &block) ⇒ Relation Originally defined in module Reading

Group by specific columns

Overloads:

  • #group(*columns) ⇒ Relation

    Return a new relation grouped by provided columns

    Examples:

    tasks.group(:user_id)

    Parameters:

    • columns (Array<Symbol>) —

      A list with column names

  • #group(*attributes) ⇒ Relation

    Return a new relation grouped by provided schema attributes

    Examples:

    tasks.group(tasks[:id], tasks[:title])

    Parameters:

  • #group(*attributes, &block) ⇒ Relation

    Return a new relation grouped by provided attributes from a block

    Examples:

    tasks.group(tasks[:id]) { title.qualified }

    Parameters:

    • attributes (Array<SQL::Attributes>) —

      A list with relation attributes

Returns:

#group_and_count(*args, &block) ⇒ Relation Originally defined in module Reading

Group by specific columns and count by group

Examples:

tasks.group_and_count(:user_id)
# => [{ user_id: 1, count: 2 }, { user_id: 2, count: 3 }]

Parameters:

  • args (Array<Symbol>) —

    A list of column names

Returns:

#group_append(*columns) ⇒ Relation #group_append(*attributes) ⇒ Relation #group_append(*attributes, &block) ⇒ Relation Originally defined in module Reading

Group by more columns

Overloads:

  • #group_append(*columns) ⇒ Relation

    Return a new relation grouped by provided columns

    Examples:

    tasks.group_append(:user_id)

    Parameters:

    • columns (Array<Symbol>) —

      A list with column names

  • #group_append(*attributes) ⇒ Relation

    Return a new relation grouped by provided schema attributes

    Examples:

    tasks.group_append(tasks[:id], tasks[:title])
  • #group_append(*attributes, &block) ⇒ Relation

    Return a new relation grouped by provided schema attributes from a block

    Examples:

    tasks.group_append(tasks[:id]) { id.qualified }

    Parameters:

Returns:

#having(conditions) ⇒ Relation #having(&block) ⇒ Relation Originally defined in module Reading

Restrict a relation to match grouping criteria

Overloads:

  • #having(conditions) ⇒ Relation

    Return a new relation with having clause from conditions hash

    Examples:

    users.
  qualified.
  left_join(tasks).
  select { [id, name, integer::count(:tasks__id).as(:task_count)] }.
  group(users[:id].qualified).
  having(task_count: 2)
  first
# {:id => 1, :name => "Jane", :task_count => 2}

    Parameters:

    • conditions (Hash) —

      A hash with conditions

  • #having(&block) ⇒ Relation

    Return a new relation with having clause created from restriction DSL

    Examples:

    users.
  qualified.
  left_join(tasks).
  select { [id, name, integer::count(:tasks__id).as(:task_count)] }.
  group(users[:id].qualified).
  having { count(id.qualified) >= 1 }.
  first
# {:id => 1, :name => "Jane", :task_count => 2}

Returns:

#import(other_sql_relation, options) ⇒ Integer #import(other, options) ⇒ Integer Originally defined in module Writing

Insert tuples from other relation

NOTE: The method implicitly uses a transaction

Examples:

users.import(new_users)

Overloads:

  • #import(other_sql_relation, options) ⇒ Integer

    If both relations uses the same gateway the INSERT ... SELECT statement will be used for importing the data

    Parameters:

  • #import(other, options) ⇒ Integer

    Import data from another relation. The source relation will be materialized before loading

    Parameters:

Returns:

  • (Integer) —

    Number of imported tuples

#insert(*args, &block) ⇒ Hash Originally defined in module Writing

Insert tuple into relation

Examples:

users.insert(name: 'Jane')

Parameters:

  • args (Hash)

Returns:

  • (Hash) —

    Inserted tuple

#invert ⇒ Relation Originally defined in module Reading

Inverts the current WHERE and HAVING clauses. If there is neither a WHERE or HAVING clause, adds a WHERE clause that is always false.

Examples:

users.exclude(name: 'Jane').invert

# this is the same as:
users.where(name: 'Jane')

Returns:

#join(dataset, join_conditions) ⇒ Relation #join(dataset, join_conditions, options) ⇒ Relation #join(relation) ⇒ Relation #join(relation, &block) ⇒ Relation Also known as: inner_join Originally defined in module Reading

Join with another relation using INNER JOIN

Overloads:

  • #join(dataset, join_conditions) ⇒ Relation

    Join with another relation using dataset name and join conditions

    Examples:

    users.join(:tasks, id: :user_id)

    Parameters:

    • dataset (Symbol) —

      Join table name

    • join_conditions (Hash) —

      A hash with join conditions

  • #join(dataset, join_conditions, options) ⇒ Relation

    Join with another relation using dataset name and join conditions with additional join options

    Examples:

    users.join(:tasks, { id: :user_id }, { table_alias: :tasks_1 })

    Parameters:

    • dataset (Symbol) —

      Join table name

    • join_conditions (Hash) —

      A hash with join conditions

    • options (Hash) —

      Additional join options

  • #join(relation) ⇒ Relation

    Join with another relation

    Join conditions are automatically set based on schema association

    Examples:

    users.join(tasks)

    Parameters:

    • relation (Relation) —

      A relation for join

  • #join(relation, &block) ⇒ Relation

    Join with another relation using DSL

    Examples:

    users.join(tasks) { |users:, tasks:|
  tasks[:user_id].is(users[:id]) & users[:name].is('John')
}

    Parameters:

    • relation (Relation) —

      A relation for join

Returns:

#last ⇒ Hash Originally defined in module Reading

Get last tuple from the relation

Examples:

users.last
# {:id => 2, :name => "Joe"}

Returns:

  • (Hash)

#left_join(dataset, left_join_conditions) ⇒ Relation #left_join(dataset, left_join_conditions, options) ⇒ Relation #left_join(relation) ⇒ Relation #join(relation, &block) ⇒ Relation Originally defined in module Reading

Join with another relation using LEFT OUTER JOIN

Overloads:

  • #left_join(dataset, left_join_conditions) ⇒ Relation

    Left_Join with another relation using dataset name and left_join conditions

    Examples:

    users.left_join(:tasks, id: :user_id)

    Parameters:

    • dataset (Symbol) —

      Left_Join table name

    • left_join_conditions (Hash) —

      A hash with left_join conditions

  • #left_join(dataset, left_join_conditions, options) ⇒ Relation

    Left_Join with another relation using dataset name and left_join conditions with additional left_join options

    Examples:

    users.left_join(:tasks, { id: :user_id }, { table_alias: :tasks_1 })

    Parameters:

    • dataset (Symbol) —

      Left_Join table name

    • left_join_conditions (Hash) —

      A hash with left_join conditions

    • options (Hash) —

      Additional left_join options

  • #left_join(relation) ⇒ Relation

    Left_Join with another relation

    Left_Join conditions are automatically set based on schema association

    Examples:

    users.left_join(tasks)

    Parameters:

    • relation (Relation) —

      A relation for left_join

  • #join(relation, &block) ⇒ Relation

    Join with another relation using DSL

    Examples:

    users.left_join(tasks) { |users:, tasks:|
  tasks[:user_id].is(users[:id]) & users[:name].is('John')
}

    Parameters:

    • relation (Relation) —

      A relation for left_join

Returns:

#limit(num) ⇒ Relation #limit(num, offset) ⇒ Relation Originally defined in module Reading

Limit a relation to a specific number of tuples

Overloads:

  • #limit(num) ⇒ Relation

    Return a new relation with the limit set to the provided num

    Examples:

    users.limit(1)

    Parameters:

    • num (Integer) —

      The limit value

  • #limit(num, offset) ⇒ Relation

    Return a new relation with the limit set to the provided num

    Examples:

    users.limit(10, 2)

    Parameters:

    • num (Integer) —

      The limit value

    • offset (Integer) —

      The offset value

Returns:

#lock(options) ⇒ SQL::Relation #lock(options) {|relation| ... } ⇒ Object Originally defined in module Reading

Lock rows with in the specified mode. Check out ROW_LOCK_MODES for the list of supported modes, keep in mind available lock modes heavily depend on the database type+version you're running on.

Overloads:

  • #lock(options) ⇒ SQL::Relation

    Options Hash (options):

    • :mode (Symbol) —

      Lock mode

    • :wait (Boolean, Integer) —

      Controls the (NO)WAIT part

    • :skip_locked (Boolean) —

      Skip locked rows

    • :of (Array, Symbol, String) —

      List of objects in the OF part

    Returns:

  • #lock(options) {|relation| ... } ⇒ Object

    Runs the block inside a transaction. The relation will be materialized and passed inside the block so that the lock will be acquired right before the block gets executed.

    Parameters:

    • options (Hash) —

      The same options as for the version without a block

    Yield Parameters:

    • relation (Array)

#map(key = nil, &block) ⇒ Object Originally defined in module Reading

Map tuples from the relation

Examples:

users.map { |user| user[:id] }
# [1, 2, 3]

users.map(:id).to_a
# [1, 2, 3]

Parameters:

  • key (Symbol) (defaults to: nil) —

    An optional name of the key for extracting values from tuples

#max(*args) ⇒ Object Originally defined in module Reading

Returns a result of SQL MAX clause.

Examples:

users.max(:age)

Parameters:

  • args (Array<Symbol>) —

    A list with column names

Returns:

  • Number

#min(*args) ⇒ Object Originally defined in module Reading

Returns a result of SQL MIN clause.

Examples:

users.min(:age)

Parameters:

  • args (Array<Symbol>) —

    A list with column names

Returns:

  • Number

#multi_insert(*args, &block) ⇒ Array<String> Originally defined in module Writing

Multi insert tuples into relation

Examples:

users.multi_insert([{name: 'Jane'}, {name: 'Jack'}])

Parameters:

  • args (Array<Hash>)

Returns:

  • (Array<String>) —

    A list of executed SQL statements

#offset(num) ⇒ Relation Originally defined in module Reading

Set offset for the relation

Examples:

users.limit(10).offset(2)

Parameters:

  • num (Integer) —

    The offset value

Returns:

#order(*columns) ⇒ Relation #order(*attributes) ⇒ Relation #order(&block) ⇒ Relation Originally defined in module Reading

Set order for the relation

Overloads:

  • #order(*columns) ⇒ Relation

    Return a new relation ordered by provided columns (ASC by default)

    Examples:

    users.order(:name, :id)

    Parameters:

    • columns (Array<Symbol>) —

      A list with column names

  • #order(*attributes) ⇒ Relation

    Return a new relation ordered by provided schema attributes

    Examples:

    users.order(self[:name].qualified.desc, self[:id].qualified.desc)

    Parameters:

    • attributes (Array<SQL::Attribute>) —

      A list with schema attributes

  • #order(&block) ⇒ Relation

    Return a new relation ordered using order DSL

    Examples:

    using attribute

    users.order { id.desc }
users.order { price.desc(nulls: :first) }

    using a function

    users.order { nullif(name.qualified, `''`).desc(nulls: :first) }

Returns:

#pluck(*names) ⇒ Array Originally defined in module Reading

Pluck values from a specific column

Examples:

Single value

users.pluck(:id)
# [1, 2]

Multiple values

users.pluck(:id, :name)
# [[1, "Jane"] [2, "Joe"]]

Returns:

  • (Array)

#prefix(name = Inflector.singularize(schema.name.dataset)) ⇒ Relation Originally defined in module Reading

Prefix all columns in a relation

This method is intended to be used internally within a relation object

Examples:

users.prefix(:user).to_a
# {:user_id => 1, :user_name => "Jane"}

Parameters:

  • name (Symbol) (defaults to: Inflector.singularize(schema.name.dataset)) —

    The prefix

Returns:

#qualified(table_alias = nil) ⇒ Relation Originally defined in module Reading

Qualifies all columns in a relation

This method is intended to be used internally within a relation object

Examples:

users.qualified.dataset.sql
# SELECT "users"."id", "users"."name" ...

Returns:

#qualified_columns ⇒ Array<Symbol> Originally defined in module Reading

Return a list of qualified column names

This method is intended to be used internally within a relation object

Examples:

users.qualified_columns
# [:users__id, :users__name]

Returns:

  • (Array<Symbol>)

#query ⇒ SQL::Attribute Originally defined in module Reading

Turn a relation into a subquery. Can be used for selecting a column with a subquery or restricting the result set with a IN (SELECT ...) condtion.

Examples:

adding number of user tasks

tasks = relations[:tasks]
users = relations[:users]
user_tasks = tasks.where(tasks[:user_id].is(users[:id]))
tasks_count = user_tasks.select { integer::count(id) }
users.select_append(tasks_count.as(:tasks_count))

Returns:

#read(sql) ⇒ SQL::Relation Originally defined in module Reading

Return a new relation from a raw SQL string

Examples:

users.read('SELECT name FROM users')

Parameters:

  • sql (String) —

    The SQL string

Returns:

#rename(options) ⇒ Relation Originally defined in module Reading

Rename columns in a relation

This method is intended to be used internally within a relation object

Examples:

users.rename(name: :user_name).first
# {:id => 1, :user_name => "Jane" }

Parameters:

  • options (Hash<Symbol=>Symbol>) —

    A name => new_name map

Returns:

#reverse(*args, &block) ⇒ Relation Originally defined in module Reading

Reverse the order of the relation

Examples:

users.order(:name).reverse

Returns:

#right_join(dataset, right_join_conditions) ⇒ Relation #right_join(dataset, right_join_conditions, options) ⇒ Relation #right_join(relation) ⇒ Relation #join(relation, &block) ⇒ Relation Originally defined in module Reading

Join with another relation using RIGHT JOIN

Overloads:

  • #right_join(dataset, right_join_conditions) ⇒ Relation

    Right_Join with another relation using dataset name and right_join conditions

    Examples:

    users.right_join(:tasks, id: :user_id)

    Parameters:

    • dataset (Symbol) —

      Right_Join table name

    • right_join_conditions (Hash) —

      A hash with right_join conditions

  • #right_join(dataset, right_join_conditions, options) ⇒ Relation

    Right_Join with another relation using dataset name and right_join conditions with additional right_join options

    Examples:

    users.right_join(:tasks, { id: :user_id }, { table_alias: :tasks_1 })

    Parameters:

    • dataset (Symbol) —

      Right_Join table name

    • right_join_conditions (Hash) —

      A hash with right_join conditions

    • options (Hash) —

      Additional right_join options

  • #right_join(relation) ⇒ Relation

    Right_Join with another relation

    Right_Join conditions are automatically set based on schema association

    Examples:

    users.right_join(tasks)

    Parameters:

    • relation (Relation) —

      A relation for right_join

  • #join(relation, &block) ⇒ Relation

    Join with another relation using DSL

    Examples:

    users.right_join(tasks) { |users:, tasks:|
  tasks[:user_id].is(users[:id]) & users[:name].is('John')
}

    Parameters:

    • relation (Relation) —

      A relation for right_join

Returns:

#select(*columns) ⇒ Relation #select(*attributes) ⇒ Relation #select(&block) ⇒ Relation #select(*columns, &block) ⇒ Relation Also known as: project Originally defined in module Reading

Select specific columns for select clause

Overloads:

  • #select(*columns) ⇒ Relation

    Project relation using column names

    Examples:

    using column names

    users.select(:id, :name).first
# {:id => 1, :name => "Jane"}

    Parameters:

    • columns (Array<Symbol>) —

      A list of column names

  • #select(*attributes) ⇒ Relation

    Project relation using schema attributes

    Examples:

    using attributes

    users.select(:id, :name).first
# {:id => 1, :name => "Jane"}

    using schema

    users.select(*schema.project(:id)).first
# {:id => 1}

    Parameters:

  • #select(&block) ⇒ Relation

    Project relation using projection DSL

    Examples:

    using attributes

    users.select { id.as(:user_id) }
# {:user_id => 1}

users.select { [id, name] }
# {:id => 1, :name => "Jane"}

    using SQL functions

    users.select { string::concat(id, '-', name).as(:uid) }.first
# {:uid => "1-Jane"}
  • #select(*columns, &block) ⇒ Relation

    Project relation using column names and projection DSL

    Examples:

    using attributes

    users.select(:id) { integer::count(id).as(:count) }.group(:id).first
# {:id => 1, :count => 1}

users.select { [id, name] }
# {:id => 1, :name => "Jane"}

    Parameters:

Returns:

#select_append(*args, &block) ⇒ Relation Originally defined in module Reading

Append specific columns to select clause

Returns:

See Also:

#select_group(*args, &block) ⇒ Relation Originally defined in module Reading

Select and group by specific columns

Examples:

tasks.select_group(:user_id)
# => [{ user_id: 1 }, { user_id: 2 }]

Parameters:

  • args (Array<Symbol>) —

    A list of column names

Returns:

#sum(*args) ⇒ Integer Originally defined in module Reading

Returns a result of SQL SUM clause.

Examples:

users.sum(:age)

Parameters:

  • args (Array<Symbol>) —

    A list with column names

Returns:

  • (Integer)

#transaction(opts = EMPTY_HASH) {|t| ... } ⇒ Mixed

Open a database transaction

Parameters:

  • opts (Hash) (defaults to: EMPTY_HASH)

Options Hash (opts):

  • :auto_savepoint (Boolean) —

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

  • :isolation (Symbol) —

    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.

  • :num_retries (Integer) —

    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.

  • :before_retry (Proc) —

    Proc to execute before rertrying 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.

  • :prepare (String) —

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

  • :retry_on (Class) —

    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.

  • :rollback (Symbol) —

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

  • :server (Symbol) —

    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.

  • :savepoint (Boolean) —

    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 transacation.

  • :deferrable (Boolean) —

    PG 9.1+ only If present, set to DEFERRABLE if true or NOT DEFERRABLE if false.

  • :read_only (Boolean) —

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

  • :synchronous (Symbol) —

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

Yields:

  • (t) —

    Transaction

Returns:

  • (Mixed) 


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# File 'lib/rom/sql/relation.rb', line 142

def transaction(opts = EMPTY_HASH, &block)
  Transaction.new(dataset.db).run(opts, &block)
end

#unfiltered ⇒ SQL::Relation Originally defined in module Reading

Discard restrictions in WHERE and HAVING clauses

Examples:

calling .by_pk has no effect

users.by_pk(1).unfiltered

Returns:

#union(relation, options = EMPTY_HASH, &block) ⇒ Object Originally defined in module Reading

Adds a UNION clause for relation dataset using second relation dataset

@returRelation]

Examples:

users.where(id: 1).union(users.where(id: 2))
# => [{ id: 1, name: 'Piotr' }, { id: 2, name: 'Jane' }]

Parameters:

  • relation (Relation) —

    Another relation

  • options (Hash) (defaults to: EMPTY_HASH) —

    Options for union

Options Hash (options):

  • :alias (Symbol) —

    Use the given value as the #from_self alias

  • :all (TrueClass, FalseClass) —

    Set to true to use UNION ALL instead of UNION, so duplicate rows can occur

  • :from_self (TrueClass, FalseClass) —

    Set to false to not wrap the returned dataset in a #from_self, use with care.

#unique?(criteria) ⇒ TrueClass, FalseClass Originally defined in module Reading

Return if a restricted relation has 0 tuples

Examples:

users.unique?(email: 'jane@doe.org') # true

users.insert(email: 'jane@doe.org')

users.unique?(email: 'jane@doe.org') # false

Parameters:

  • criteria (Hash) —

    The condition hash for WHERE clause

Returns:

  • (TrueClass, FalseClass)

#update(*args, &block) ⇒ Integer Originally defined in module Writing

Update tuples in the relation

Examples:

users.update(name: 'Jane')
users.where(name: 'Jane').update(name: 'Jane Doe')

Returns:

  • (Integer) —

    Number of updated rows

#upsert(*args, &block) ⇒ Integer Originally defined in module Writing

Add upsert option (only PostgreSQL >= 9.5) Uses internal Sequel implementation Default - ON CONFLICT DO NOTHING more options: http://sequel.jeremyevans.net/rdoc-adapters/classes/Sequel/Postgres/DatasetMethods.html#method-i-insert_conflict

Examples:

users.upsert({ name: 'Jane', email: 'jane@foo.com' },
             { target: :email, update: { name: :excluded__name } })

Returns:

  • (Integer) —

    Number of affected rows

#where(conditions) ⇒ Relation #where(conditions, &block) ⇒ Relation #where(&block) ⇒ Relation Originally defined in module Reading

Restrict a relation to match criteria

Overloads:

  • #where(conditions) ⇒ Relation

    Restrict a relation using a hash with conditions

    Examples:

    users.where(name: 'Jane', age: 30)

    Parameters:

    • conditions (Hash) —

      A hash with conditions

  • #where(conditions, &block) ⇒ Relation

    Restrict a relation using a hash with conditions and restriction DSL

    Examples:

    users.where(name: 'Jane') { age > 18 }

    Parameters:

    • conditions (Hash) —

      A hash with conditions

  • #where(&block) ⇒ Relation

    Restrict a relation using restriction DSL

    Examples:

    users.where { age > 18 }
users.where { (id < 10) | (id > 20) }

Returns:

#wrap(*names) ⇒ Wrap Originally defined in module Reading

Wrap other relations using association names

Examples:

tasks.wrap(:owner)

Parameters:

  • names (Array<Symbol>) —

    A list with association identifiers

Returns: