Class: Sequel::Dataset

Inherits:
Object show all
Extended by:
Metaprogramming
Includes:
Enumerable, Metaprogramming
Defined in:
lib/sequel/dataset.rb,
lib/sequel/deprecated.rb,
lib/sequel/dataset/sql.rb,
lib/sequel/object_graph.rb,
lib/sequel/extensions/query.rb,
lib/sequel/dataset/convenience.rb,
lib/sequel/extensions/pagination.rb,
lib/sequel/extensions/pretty_table.rb,
lib/sequel/adapters/utils/unsupported.rb,
lib/sequel/dataset/prepared_statements.rb,
lib/sequel/adapters/utils/stored_procedures.rb

Overview

A Dataset represents a view of a the data in a database, constrained by specific parameters such as filtering conditions, order, etc. Datasets can be used to create, retrieve, update and delete records.

Query results are always retrieved on demand, so a dataset can be kept around and reused indefinitely:

my_posts = DB[:posts].filter(:author => 'david') # no records are retrieved
p my_posts.all # records are now retrieved
...
p my_posts.all # records are retrieved again

In order to provide this functionality, dataset methods such as where, select, order, etc. return modified copies of the dataset, so you can use different datasets to access data:

posts = DB[:posts]
davids_posts = posts.filter(:author => 'david')
old_posts = posts.filter('stamp < ?', Date.today - 7)

Datasets are Enumerable objects, so they can be manipulated using any of the Enumerable methods, such as map, inject, etc.

Methods added via metaprogramming

Some methods are added via metaprogramming:

  • ! methods - These methods are the same as their non-! counterparts, but they modify the receiver instead of returning a modified copy of the dataset.

  • inner_join, full_outer_join, right_outer_join, left_outer_join - This methods are shortcuts to join_table with the join type already specified.

Defined Under Namespace

Modules: ArgumentMapper, Pagination, PreparedStatementMethods, QueryBlockCopy, SQLStandardDateFormat, StoredProcedureMethods, StoredProcedures, UnnumberedArgumentMapper, UnsupportedIntersectExcept, UnsupportedIntersectExceptAll, UnsupportedIsTrue

Constant Summary collapse

COLUMN_CHANGE_OPTS =

The dataset options that require the removal of cached columns if changed.

[:select, :sql, :from, :join].freeze
MUTATION_METHODS =

All methods that should have a ! method added that modifies the receiver.

%w'add_graph_aliases and distinct exclude exists
filter from from_self full_outer_join graph
group group_and_count group_by having inner_join intersect invert join
left_outer_join limit naked or order order_by order_more paginate query reject
reverse reverse_order right_outer_join select select_all select_more
set_defaults set_graph_aliases set_overrides sort sort_by
unfiltered union unordered where with_sql'.collect{|x| x.to_sym}
NOTIMPL_MSG = 
"This method must be overridden in Sequel adapters".freeze
STOCK_TRANSFORMS = 
{
  :marshal => [
    # for backwards-compatibility we support also non-base64-encoded values.
    proc {|v| Marshal.load(v.unpack('m')[0]) rescue Marshal.load(v)}, 
    proc {|v| [Marshal.dump(v)].pack('m')}
  ],
  :yaml => [
    proc {|v| YAML.load v if v}, 
    proc {|v| v.to_yaml}
  ]
}
DATASET_CLASSES = 
[]
AND_SEPARATOR = 
" AND ".freeze
BOOL_FALSE = 
"'f'".freeze
BOOL_TRUE = 
"'t'".freeze
COLUMN_REF_RE1 = 
/\A([\w ]+)__([\w ]+)___([\w ]+)\z/.freeze
COLUMN_REF_RE2 = 
/\A([\w ]+)___([\w ]+)\z/.freeze
COLUMN_REF_RE3 = 
/\A([\w ]+)__([\w ]+)\z/.freeze
COUNT_FROM_SELF_OPTS = 
[:distinct, :group, :sql, :limit, :compounds]
IS_LITERALS = 
{nil=>'NULL'.freeze, true=>'TRUE'.freeze, false=>'FALSE'.freeze}.freeze
IS_OPERATORS = 
::Sequel::SQL::ComplexExpression::IS_OPERATORS
N_ARITY_OPERATORS = 
::Sequel::SQL::ComplexExpression::N_ARITY_OPERATORS
NULL = 
"NULL".freeze
QUESTION_MARK = 
'?'.freeze
STOCK_COUNT_OPTS = 
{:select => [LiteralString.new("COUNT(*)").freeze], :order => nil}.freeze
SELECT_CLAUSE_ORDER = 
%w'distinct columns from join where group having compounds order limit'.freeze
TWO_ARITY_OPERATORS = 
::Sequel::SQL::ComplexExpression::TWO_ARITY_OPERATORS
WILDCARD = 
'*'.freeze
COMMA_SEPARATOR = 
', '.freeze
COUNT_OF_ALL_AS_COUNT = 
SQL::Function.new(:count, LiteralString.new('*'.freeze)).as(:count)
PREPARED_ARG_PLACEHOLDER = 
LiteralString.new('?').freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Metaprogramming

meta_def

Methods included from Enumerable

#send_each

Constructor Details

#initialize(db, opts = nil) ⇒ Dataset

Constructs a new instance of a dataset with an associated database and options. Datasets are usually constructed by invoking Database methods:

DB[:posts]

Or:

DB.dataset # the returned dataset is blank

Sequel::Dataset is an abstract class that is not useful by itself. Each database adaptor should provide a descendant class of Sequel::Dataset.



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# File 'lib/sequel/dataset.rb', line 98

def initialize(db, opts = nil)
  @db = db
  @quote_identifiers = db.quote_identifiers? if db.respond_to?(:quote_identifiers?)
  @identifier_input_method = db.identifier_input_method if db.respond_to?(:identifier_input_method)
  @identifier_output_method = db.identifier_output_method if db.respond_to?(:identifier_output_method)
  @opts = opts || {}
  @row_proc = nil
  @transform = nil
end

Instance Attribute Details

#db ⇒ Object

The database that corresponds to this dataset



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# File 'lib/sequel/dataset.rb', line 68

def db
  @db
end

#identifier_input_method ⇒ Object

Set the method to call on identifiers going into the database for this dataset



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# File 'lib/sequel/dataset.rb', line 71

def identifier_input_method
  @identifier_input_method
end

#identifier_output_method ⇒ Object

Set the method to call on identifiers coming the database for this dataset



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# File 'lib/sequel/dataset.rb', line 74

def identifier_output_method
  @identifier_output_method
end

#opts ⇒ Object

The hash of options for this dataset, keys are symbols.



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# File 'lib/sequel/dataset.rb', line 77

def opts
  @opts
end

#quote_identifiers=(value) ⇒ Object (writeonly)

Whether to quote identifiers for this dataset



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# File 'lib/sequel/dataset.rb', line 80

def quote_identifiers=(value)
  @quote_identifiers = value
end

#row_proc ⇒ Object

The row_proc for this database, should be a Proc that takes a single hash argument and returns the object you want to fetch_rows to return.



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# File 'lib/sequel/dataset.rb', line 85

def row_proc
  @row_proc
end

Class Method Details

.dataset_classes ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 89

def self.dataset_classes
  Deprecation.deprecate('Sequel::Dataset#dataset_classes', 'No replacement is planned')
  DATASET_CLASSES
end

.def_mutation_method(*meths) ⇒ Object

Setup mutation (e.g. filter!) methods. These operate the same as the non-! methods, but replace the options of the current dataset with the options of the resulting dataset.



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# File 'lib/sequel/dataset.rb', line 113

def self.def_mutation_method(*meths)
  meths.each do |meth|
    class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end")
  end
end

.inherited(c) ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 94

def self.inherited(c)
  DATASET_CLASSES << c
end

Instance Method Details

#<<(*args) ⇒ Object

Alias for insert, but not aliased directly so subclasses don’t have to override both methods.



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# File 'lib/sequel/dataset.rb', line 123

def <<(*args)
  insert(*args)
end

#[](*conditions) ⇒ Object

Returns the first record matching the conditions.



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# File 'lib/sequel/dataset/convenience.rb', line 7

def [](*conditions)
  Deprecation.deprecate('Using an Integer argument to Dataset#[] is deprecated and will raise an error in a future version. Use Dataset#first.') if conditions.length == 1 and conditions.is_a?(Integer)
  first(*conditions)
end

#[]=(conditions, values) ⇒ Object

Update all records matching the conditions with the values specified.



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# File 'lib/sequel/dataset/convenience.rb', line 14

def []=(conditions, values)
  filter(conditions).update(values)
end

#add_graph_aliases(graph_aliases) ⇒ Object

Adds the give graph aliases to the list of graph aliases to use, unlike #set_graph_aliases, which replaces the list. See #set_graph_aliases.



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# File 'lib/sequel/object_graph.rb', line 167

def add_graph_aliases(graph_aliases)
  ds = select_more(*graph_alias_columns(graph_aliases))
  ds.opts[:graph_aliases] = (ds.opts[:graph_aliases] || {}).merge(graph_aliases)
  ds
end

#aliased_expression_sql(ae) ⇒ Object

SQL fragment for the aliased expression



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# File 'lib/sequel/dataset/sql.rb', line 29

def aliased_expression_sql(ae)
  as_sql(literal(ae.expression), ae.aliaz)
end

#all(opts = (defarg=true;nil), &block) ⇒ Object

Returns an array with all records in the dataset. If a block is given, the array is iterated over after all items have been loaded.



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# File 'lib/sequel/dataset.rb', line 135

def all(opts = (defarg=true;nil), &block)
  Deprecation.deprecate("Calling Dataset#all with an argument is deprecated and will raise an error in a future version.  Use dataset.clone(opts).all.") unless defarg
  a = []
  defarg ? each{|r| a << r} : each(opts){|r| a << r}
  post_load(a)
  a.each(&block) if block
  a
end

#and(*cond, &block) ⇒ Object

Adds an further filter to an existing filter using AND. If no filter exists an error is raised. This method is identical to #filter except it expects an existing filter.

Raises:



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# File 'lib/sequel/dataset/sql.rb', line 23

def and(*cond, &block)
  raise(Error::NoExistingFilter, "No existing filter found.") unless @opts[:having] || @opts[:where]
  filter(*cond, &block)
end

#array_sql(a) ⇒ Object

SQL fragment for the SQL array.



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# File 'lib/sequel/dataset/sql.rb', line 34

def array_sql(a)
  a.empty? ? '(NULL)' : "(#{expression_list(a)})"     
end

#as(aliaz) ⇒ Object

Return the dataset as a column with the given alias, so it can be used in the SELECT clause. This dataset should result in a single row and a single column.



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# File 'lib/sequel/dataset.rb', line 129

def as(aliaz)
  ::Sequel::SQL::AliasedExpression.new(self, aliaz)
end

#avg(column) ⇒ Object

Returns the average value for the given column.



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# File 'lib/sequel/dataset/convenience.rb', line 19

def avg(column)
  get{|o| o.avg(column)}
end

#call(type, bind_variables = {}, values = nil) ⇒ Object

For the given type (:select, :insert, :update, or :delete), run the sql with the bind variables specified in the hash. values is a hash of passed to insert or update (if one of those types is used), which may contain placeholders.



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# File 'lib/sequel/dataset/prepared_statements.rb', line 181

def call(type, bind_variables={}, values=nil)
  prepare(type, nil, values).call(bind_variables)
end

#case_expression_sql(ce) ⇒ Object

SQL fragment for specifying given CaseExpression.



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# File 'lib/sequel/dataset/sql.rb', line 39

def case_expression_sql(ce)
  sql = '(CASE '
  sql << "#{literal(ce.expression)} " if ce.expression
  ce.conditions.collect{ |c,r|
    sql << "WHEN #{literal(c)} THEN #{literal(r)} "
  }
  sql << "ELSE #{literal(ce.default)} END)"
end

#cast_sql(expr, type) ⇒ Object

SQL fragment for the SQL CAST expression.



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# File 'lib/sequel/dataset/sql.rb', line 49

def cast_sql(expr, type)
  "CAST(#{literal(expr)} AS #{db.send(:type_literal_base, :type=>type)})"
end

#clone(opts = {}) ⇒ Object

Returns a new clone of the dataset with with the given options merged. If the options changed include options in COLUMN_CHANGE_OPTS, the cached columns are deleted.



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# File 'lib/sequel/dataset.rb', line 147

def clone(opts = {})
  c = super()
  c.opts = @opts.merge(opts)
  c.instance_variable_set(:@columns, nil) if opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
  c
end

#column_all_sql(ca) ⇒ Object

SQL fragment for specifying all columns in a given table.



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# File 'lib/sequel/dataset/sql.rb', line 54

def column_all_sql(ca)
  "#{quote_schema_table(ca.table)}.*"
end

#columns ⇒ Object

Returns the columns in the result set in their true order. If the columns are currently cached, returns the cached value. Otherwise, a SELECT query is performed to get a single row. Adapters are expected to fill the columns cache with the column information when a query is performed. If the dataset does not have any rows, this will be an empty array. If you are looking for all columns for a single table, see Database#schema.



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# File 'lib/sequel/dataset.rb', line 160

def columns
  return @columns if @columns
  ds = unfiltered.unordered.clone(:distinct => nil, :limit => 1)
  ds.each{break}
  @columns = ds.instance_variable_get(:@columns)
  @columns || []
end

#columns! ⇒ Object

Remove the cached list of columns and do a SELECT query to find the columns.



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# File 'lib/sequel/dataset.rb', line 170

def columns!
  @columns = nil
  columns
end

#complex_expression_sql(op, args) ⇒ Object

SQL fragment for complex expressions



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# File 'lib/sequel/dataset/sql.rb', line 59

def complex_expression_sql(op, args)
  case op
  when *IS_OPERATORS
    v = IS_LITERALS[args.at(1)] || raise(Error, 'Invalid argument used for IS operator')
    "(#{literal(args.at(0))} #{op} #{v})"
  when *TWO_ARITY_OPERATORS
    "(#{literal(args.at(0))} #{op} #{literal(args.at(1))})"
  when *N_ARITY_OPERATORS
    "(#{args.collect{|a| literal(a)}.join(" #{op} ")})"
  when :NOT
    "NOT #{literal(args.at(0))}"
  when :NOOP
    literal(args.at(0))
  when :'B~'
    "~#{literal(args.at(0))}"
  else
    raise(Sequel::Error, "invalid operator #{op}")
  end
end

#count ⇒ Object

Returns the number of records in the dataset.



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# File 'lib/sequel/dataset/sql.rb', line 80

def count
  options_overlap(COUNT_FROM_SELF_OPTS) ? from_self.count : clone(STOCK_COUNT_OPTS).single_value.to_i
end

#create_or_replace_view(name) ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 165

def create_or_replace_view(name)
  Sequel::Deprecation.deprecate('Sequel::Dataset#create_or_replace_view', 'Use Sequel::Database#create_or_replace_view')
  @db.create_or_replace_view(name, self)
end

#create_view(name) ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 160

def create_view(name)
  Sequel::Deprecation.deprecate('Sequel::Dataset#create_view', 'Use Sequel::Database#create_view')
  @db.create_view(name, self)
end

#def_mutation_method(*meths) ⇒ Object

Add a mutation method to this dataset instance.



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# File 'lib/sequel/dataset.rb', line 176

def def_mutation_method(*meths)
  meths.each do |meth|
    instance_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end")
  end
end

#delete(opts = (defarg=true;nil)) ⇒ Object

Deletes the records in the dataset. The returned value is generally the number of records deleted, but that is adapter dependent.



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# File 'lib/sequel/dataset.rb', line 184

def delete(opts=(defarg=true;nil))
  Deprecation.deprecate("Calling Dataset#delete with an argument is deprecated and will raise an error in a future version.  Use dataset.clone(opts).delete.") unless defarg
  execute_dui(defarg ? delete_sql : delete_sql(opts))
end

#delete_sql(opts = (defarg=true;nil)) ⇒ Object

Formats a DELETE statement using the given options and dataset options.

dataset.filter{|o| o.price >= 100}.delete_sql #=>
  "DELETE FROM items WHERE (price >= 100)"



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# File 'lib/sequel/dataset/sql.rb', line 88

def delete_sql(opts = (defarg=true;nil))
  Deprecation.deprecate("Calling Dataset#delete_sql with an argument is deprecated and will raise an error in a future version.  Use dataset.clone(opts).delete_sql.") unless defarg
  opts = opts ? @opts.merge(opts) : @opts

  return static_sql(opts[:sql]) if opts[:sql]

  if opts[:group]
    raise Error::InvalidOperation, "Grouped datasets cannot be deleted from"
  elsif opts[:from].is_a?(Array) && opts[:from].size > 1
    raise Error::InvalidOperation, "Joined datasets cannot be deleted from"
  end

  sql = "DELETE FROM #{source_list(opts[:from])}"

  if where = opts[:where]
    sql << " WHERE #{literal(where)}"
  end

  sql
end

#distinct(*args) ⇒ Object

Returns a copy of the dataset with the SQL DISTINCT clause. The DISTINCT clause is used to remove duplicate rows from the output. If arguments are provided, uses a DISTINCT ON clause, in which case it will only be distinct on those columns, instead of all returned columns.



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# File 'lib/sequel/dataset/sql.rb', line 114

def distinct(*args)
  clone(:distinct => args)
end

#each(opts = (defarg=true;nil), &block) ⇒ Object

Iterates over the records in the dataset and returns set. If opts have been passed that modify the columns, reset the column information.



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# File 'lib/sequel/dataset.rb', line 191

def each(opts = (defarg=true;nil), &block)
  Deprecation.deprecate("Calling Dataset#each with an argument is deprecated and will raise an error in a future version.  Use dataset.clone(opts).each.") unless defarg
  if opts && opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
    prev_columns = @columns
    begin
      defarg ? _each(&block) : _each(opts, &block)
    ensure
      @columns = prev_columns
    end
  else
    defarg ? _each(&block) : _each(opts, &block)
  end
  self
end

#each_page(page_size, &block) ⇒ Object

Yields a paginated dataset for each page and returns the receiver. Does a count to find the total number of records for this dataset.

Raises:



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# File 'lib/sequel/extensions/pagination.rb', line 16

def each_page(page_size, &block)
  Sequel::Deprecation.deprecate('Sequel::Dataset#each_page', 'require "sequel/extensions/pagination" first')
  raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
  record_count = count
  total_pages = (record_count / page_size.to_f).ceil
  (1..total_pages).each{|page_no| yield paginate(page_no, page_size, record_count)}
  self
end

#empty? ⇒ Boolean

Returns true if no records exists in the dataset

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/convenience.rb', line 24

def empty?
  get(1).nil?
end

#except(dataset, all = false) ⇒ Object

Adds an EXCEPT clause using a second dataset object. If all is true the clause used is EXCEPT ALL, which may return duplicate rows.

DB[:items].except(DB[:other_items]).sql
#=> "SELECT * FROM items EXCEPT SELECT * FROM other_items"



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# File 'lib/sequel/dataset/sql.rb', line 123

def except(dataset, all = false)
  compound_clone(:except, dataset, all)
end

#exclude(*cond, &block) ⇒ Object

Performs the inverse of Dataset#filter.

dataset.exclude(:category => 'software').sql #=>
  "SELECT * FROM items WHERE (category != 'software')"



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# File 'lib/sequel/dataset/sql.rb', line 131

def exclude(*cond, &block)
  clause = (@opts[:having] ? :having : :where)
  cond = cond.first if cond.size == 1
  cond = cond.sql_or if (Hash === cond) || ((Array === cond) && (cond.all_two_pairs?))
  cond = filter_expr(cond, &block)
  cond = SQL::BooleanExpression.invert(cond)
  cond = SQL::BooleanExpression.new(:AND, @opts[clause], cond) if @opts[clause]
  clone(clause => cond)
end

#exists(opts = (defarg=true;nil)) ⇒ Object

Returns an EXISTS clause for the dataset as a LiteralString.

DB.select(1).where(DB[:items].exists).sql
#=> "SELECT 1 WHERE EXISTS (SELECT * FROM items)"



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# File 'lib/sequel/dataset/sql.rb', line 145

def exists(opts = (defarg=true;nil))
  Deprecation.deprecate("Calling Dataset#exists with an argument is deprecated and will raise an error in a future version.  Use dataset.clone(opts).exists.") unless defarg
  LiteralString.new("EXISTS (#{defarg ? select_sql : select_sql(opts)})")
end

#fetch_rows(sql, &block) ⇒ Object

Executes a select query and fetches records, passing each record to the supplied block. The yielded records are generally hashes with symbol keys, but that is adapter dependent.

Raises:

  • (NotImplementedError) 


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# File 'lib/sequel/dataset.rb', line 209

def fetch_rows(sql, &block)
  raise NotImplementedError, NOTIMPL_MSG
end

#filter(*cond, &block) ⇒ Object

Returns a copy of the dataset with the given conditions imposed upon it.

If the query already has a HAVING clause, then the conditions are imposed in the HAVING clause. If not, then they are imposed in the WHERE clause.

filter accepts the following argument types:

  • Hash - list of equality/inclusion expressions

  • Array - depends:

    • If first member is a string, assumes the rest of the arguments are parameters and interpolates them into the string.

    • If all members are arrays of length two, treats the same way as a hash, except it allows for duplicate keys to be specified.

  • String - taken literally

  • Symbol - taken as a boolean column argument (e.g. WHERE active)

  • Sequel::SQL::BooleanExpression - an existing condition expression, probably created using the Sequel expression filter DSL.

filter also takes a block, which should return one of the above argument types, and is treated the same way. If both a block and regular argument are provided, they get ANDed together.

Examples:

dataset.filter(:id => 3).sql #=>
  "SELECT * FROM items WHERE (id = 3)"
dataset.filter('price < ?', 100).sql #=>
  "SELECT * FROM items WHERE price < 100"
dataset.filter([[:id, (1,2,3)], [:id, 0..10]]).sql #=>
  "SELECT * FROM items WHERE ((id IN (1, 2, 3)) AND ((id >= 0) AND (id <= 10)))"
dataset.filter('price < 100').sql #=>
  "SELECT * FROM items WHERE price < 100"
dataset.filter(:active).sql #=>
  "SELECT * FROM items WHERE :active
dataset.filter{|o| o.price < 100}.sql #=>
  "SELECT * FROM items WHERE (price < 100)"

Multiple filter calls can be chained for scoping:

software = dataset.filter(:category => 'software')
software.filter{|o| o.price < 100}.sql #=>
  "SELECT * FROM items WHERE ((category = 'software') AND (price < 100))"

See doc/dataset_filters.rdoc for more examples and details.



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# File 'lib/sequel/dataset/sql.rb', line 194

def filter(*cond, &block)
  _filter(@opts[:having] ? :having : :where, *cond, &block)
end

#first(*args, &block) ⇒ Object

Returns the first record in the dataset. If a numeric argument is given, it is interpreted as a limit, and then returns all matching records up to that limit. If no argument is passed, it returns the first matching record. If any other type of argument(s) is passed, it is given to filter and the first matching record is returned. If a block is given, it is used to filter the dataset before returning anything.

Examples:

ds.first => {:id=>7}
ds.first(2) => [{:id=>6}, {:id=>4}]
ds.order(:id).first(2) => [{:id=>1}, {:id=>2}]
ds.first(:id=>2) => {:id=>2}
ds.first("id = 3") => {:id=>3}
ds.first("id = ?", 4) => {:id=>4}
ds.first{|o| o.id > 2} => {:id=>5}
ds.order(:id).first{|o| o.id > 2} => {:id=>3}
ds.first{|o| o.id > 2} => {:id=>5}
ds.first("id > ?", 4){|o| o.id < 6} => {:id=>5}
ds.order(:id).first(2){|o| o.id < 2} => [{:id=>1}]



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# File 'lib/sequel/dataset/convenience.rb', line 49

def first(*args, &block)
  ds = block ? filter(&block) : self

  if args.empty?
    ds.single_record
  else
    args = (args.size == 1) ? args.first : args
    if Integer === args
      ds.limit(args).all
    else
      ds.filter(args).single_record
    end
  end
end

#first_source ⇒ Object

The first source (primary table) for this dataset. If the dataset doesn’t have a table, raises an error. If the table is aliased, returns the aliased name.



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# File 'lib/sequel/dataset/sql.rb', line 200

def first_source
  source = @opts[:from]
  if source.nil? || source.empty?
    raise Error, 'No source specified for query'
  end
  case s = source.first
  when Hash
    s.values.first
  when Symbol
    sch, table, aliaz = split_symbol(s)
    aliaz ? aliaz.to_sym : s
  else
    s
  end
end

#from(*source) ⇒ Object

Returns a copy of the dataset with the source changed.



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# File 'lib/sequel/dataset/sql.rb', line 217

def from(*source)
  clone(:from => source)
end

#from_self ⇒ Object

Returns a dataset selecting from the current dataset.

ds = DB[:items].order(:name)
ds.sql #=> "SELECT * FROM items ORDER BY name"
ds.from_self.sql #=> "SELECT * FROM (SELECT * FROM items ORDER BY name)"



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# File 'lib/sequel/dataset/sql.rb', line 226

def from_self
  fs = {}
  @opts.keys.each{|k| fs[k] = nil} 
  fs[:from] = [self]
  clone(fs)
end

#function_sql(f) ⇒ Object

SQL fragment specifying an SQL function call



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# File 'lib/sequel/dataset/sql.rb', line 234

def function_sql(f)
  args = f.args
  "#{f.f}#{args.empty? ? '()' : literal(args)}"
end

#get(column = nil, &block) ⇒ Object

Return the column value for the first matching record in the dataset.

Raises:



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# File 'lib/sequel/dataset/convenience.rb', line 65

def get(column=nil, &block)
  raise(Error, 'must provide argument or block to Dataset#get, not both') if column && block
  (column ? select(column) : select(&block)).single_value
end

#graph(dataset, join_conditions = nil, options = {}, &block) ⇒ Object

Allows you to join multiple datasets/tables and have the result set split into component tables.

This differs from the usual usage of join, which returns the result set as a single hash. For example:

# CREATE TABLE artists (id INTEGER, name TEXT);
# CREATE TABLE albums (id INTEGER, name TEXT, artist_id INTEGER);
DB[:artists].left_outer_join(:albums, :artist_id=>:id).first
=> {:id=>(albums.id||artists.id), :name=>(albums.name||artist.names), :artist_id=>albums.artist_id}
DB[:artists].graph(:albums, :artist_id=>:id).first
=> {:artists=>{:id=>artists.id, :name=>artists.name}, :albums=>{:id=>albums.id, :name=>albums.name, :artist_id=>albums.artist_id}}

Using a join such as left_outer_join, the attribute names that are shared between the tables are combined in the single return hash. You can get around that by using .select with correct aliases for all of the columns, but it is simpler to use graph and have the result set split for you. In addition, graph respects any row_proc or transform attributes of the current dataset and the datasets you use with graph.

If you are graphing a table and all columns for that table are nil, this indicates that no matching rows existed in the table, so graph will return nil instead of a hash with all nil values:

# If the artist doesn't have any albums
DB[:artists].graph(:albums, :artist_id=>:id).first
=> {:artists=>{:id=>artists.id, :name=>artists.name}, :albums=>nil}

Arguments:

  • dataset - Can be a symbol (specifying a table), another dataset, or an object that responds to .dataset and yields a symbol or a dataset

  • join_conditions - Any condition(s) allowed by join_table.

  • options - A hash of graph options. The following options are currently used:

    • :implicit_qualifier - The qualifier of implicit conditions, see #join_table.

    • :join_type - The type of join to use (passed to join_table). Defaults to :left_outer.

    • :select - An array of columns to select. When not used, selects all columns in the given dataset. When set to false, selects no columns and is like simply joining the tables, though graph keeps some metadata about join that makes it important to use graph instead of join.

    • :table_alias - The alias to use for the table. If not specified, doesn’t alias the table. You will get an error if the the alias (or table) name is used more than once.

  • block - A block that is passed to join_table.



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# File 'lib/sequel/object_graph.rb', line 48

def graph(dataset, join_conditions = nil, options = {}, &block)
  # Allow the use of a model, dataset, or symbol as the first argument
  # Find the table name/dataset based on the argument
  dataset = dataset.dataset if dataset.respond_to?(:dataset)
  case dataset
  when Symbol
    table = dataset
    dataset = @db[dataset]
  when ::Sequel::Dataset
    table = dataset.first_source
  else
    raise Error, "The dataset argument should be a symbol, dataset, or model"
  end

  # Raise Sequel::Error with explanation that the table alias has been used
  raise_alias_error = lambda do
    raise(Error, "this #{options[:table_alias] ? 'alias' : 'table'} has already been been used, please specify " \
      "#{options[:table_alias] ? 'a different alias' : 'an alias via the :table_alias option'}") 
  end

  # Only allow table aliases that haven't been used
  table_alias = options[:table_alias] || table
  raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)

  # Join the table early in order to avoid cloning the dataset twice
  ds = join_table(options[:join_type] || :left_outer, table, join_conditions, :table_alias=>table_alias, :implicit_qualifier=>options[:implicit_qualifier], &block)
  opts = ds.opts

  # Whether to include the table in the result set
  add_table = options[:select] == false ? false : true
  # Whether to add the columns to the list of column aliases
  add_columns = !ds.opts.include?(:graph_aliases)

  # Setup the initial graph data structure if it doesn't exist
  unless graph = opts[:graph]
    master = ds.first_source
    raise_alias_error.call if master == table_alias
    # Master hash storing all .graph related information
    graph = opts[:graph] = {}
    # Associates column aliases back to tables and columns
    column_aliases = graph[:column_aliases] = {}
    # Associates table alias (the master is never aliased)
    table_aliases = graph[:table_aliases] = {master=>self}
    # Keep track of the alias numbers used
    ca_num = graph[:column_alias_num] = Hash.new(0)
    # All columns in the master table are never
    # aliased, but are not included if set_graph_aliases
    # has been used.
    if add_columns
      select = opts[:select] = []
      columns.each do |column|
        column_aliases[column] = [master, column]
        select.push(column.qualify(master))
      end
    end
  end

  # Add the table alias to the list of aliases
  # Even if it isn't been used in the result set,
  # we add a key for it with a nil value so we can check if it
  # is used more than once
  table_aliases = graph[:table_aliases]
  table_aliases[table_alias] = add_table ? dataset : nil

  # Add the columns to the selection unless we are ignoring them
  if add_table && add_columns
    select = opts[:select]
    column_aliases = graph[:column_aliases]
    ca_num = graph[:column_alias_num]
    # Which columns to add to the result set
    cols = options[:select] || dataset.columns
    # If the column hasn't been used yet, don't alias it.
    # If it has been used, try table_column.
    # If that has been used, try table_column_N 
    # using the next value of N that we know hasn't been
    # used
    cols.each do |column|
      col_alias, identifier = if column_aliases[column]
        column_alias = :"#{table_alias}_#{column}"
        if column_aliases[column_alias]
          column_alias_num = ca_num[column_alias]
          column_alias = :"#{column_alias}_#{column_alias_num}" 
          ca_num[column_alias] += 1
        end
        [column_alias, column.qualify(table_alias).as(column_alias)]
      else
        [column, column.qualify(table_alias)]
      end
      column_aliases[col_alias] = [table_alias, column]
      select.push(identifier)
    end
  end
  ds
end

#grep(cols, terms) ⇒ Object

Pattern match any of the columns to any of the terms. The terms can be strings (which use LIKE) or regular expressions (which are only supported in some databases). See Sequel::SQL::StringExpression.like. Note that the total number of pattern matches will be cols.length * terms.length, which could cause performance issues.



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# File 'lib/sequel/dataset/sql.rb', line 244

def grep(cols, terms)
  filter(SQL::BooleanExpression.new(:OR, *Array(cols).collect{|c| SQL::StringExpression.like(c, *terms)}))
end

#group(*columns) ⇒ Object Also known as: group_by

Returns a copy of the dataset with the results grouped by the value of the given columns



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# File 'lib/sequel/dataset/sql.rb', line 250

def group(*columns)
  clone(:group => columns)
end

#group_and_count(*columns) ⇒ Object

Returns a dataset grouped by the given column with count by group.



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# File 'lib/sequel/dataset/convenience.rb', line 71

def group_and_count(*columns)
  group(*columns).select(*(columns + [COUNT_OF_ALL_AS_COUNT])).order(:count)
end

#having(*cond, &block) ⇒ Object

Returns a copy of the dataset with the HAVING conditions changed. Raises an error if the dataset has not been grouped. See #filter for argument types.

Raises:



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# File 'lib/sequel/dataset/sql.rb', line 257

def having(*cond, &block)
  raise(Error::InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group]
  _filter(:having, *cond, &block)
end

#import(*args, &block) ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 170

def import(*args, &block)
  Sequel::Deprecation.deprecate('Sequel::Dataset#import', 'Use Sequel::Dataset#multi_insert')
  multi_insert(*args, &block)
end

#insert(*values) ⇒ Object

Inserts values into the associated table. The returned value is generally the value of the primary key for the inserted row, but that is adapter dependent.



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# File 'lib/sequel/dataset.rb', line 215

def insert(*values)
  execute_insert(insert_sql(*values))
end

#insert_multiple(array, &block) ⇒ Object

Inserts multiple values. If a block is given it is invoked for each item in the given array before inserting it. See #multi_insert as a possible faster version that inserts multiple records in one SQL statement.



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# File 'lib/sequel/dataset/sql.rb', line 266

def insert_multiple(array, &block)
  if block
    array.each {|i| insert(block[i])}
  else
    array.each {|i| insert(i)}
  end
end

#insert_sql(*values) ⇒ Object

Formats an INSERT statement using the given values. If a hash is given, the resulting statement includes column names. If no values are given, the resulting statement includes a DEFAULT VALUES clause.

dataset.insert_sql() #=> 'INSERT INTO items DEFAULT VALUES'
dataset.insert_sql(1,2,3) #=> 'INSERT INTO items VALUES (1, 2, 3)'
dataset.insert_sql(:a => 1, :b => 2) #=>
  'INSERT INTO items (a, b) VALUES (1, 2)'



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# File 'lib/sequel/dataset/sql.rb', line 282

def insert_sql(*values)
  return static_sql(@opts[:sql]) if @opts[:sql]

  from = source_list(@opts[:from])
  case values.size
  when 0
    values = {}
  when 1
    vals = values.at(0)
    if [Hash, Dataset, Array].any?{|c| vals.is_a?(c)}
      values = vals
    elsif vals.respond_to?(:values)
      values = vals.values
    end
  end

  case values
  when Array
    if values.empty?
      insert_default_values_sql
    else
      "INSERT INTO #{from} VALUES #{literal(values)}"
    end
  when Hash
    values = @opts[:defaults].merge(values) if @opts[:defaults]
    values = values.merge(@opts[:overrides]) if @opts[:overrides]
    values = transform_save(values) if @transform
    if values.empty?
      insert_default_values_sql
    else
      fl, vl = [], []
      values.each do |k, v|
        fl << literal(String === k ? k.to_sym : k)
        vl << literal(v)
      end
      "INSERT INTO #{from} (#{fl.join(COMMA_SEPARATOR)}) VALUES (#{vl.join(COMMA_SEPARATOR)})"
    end
  when Dataset
    "INSERT INTO #{from} #{literal(values)}"
  end
end

#inspect ⇒ Object

Returns a string representation of the dataset including the class name and the corresponding SQL select statement.



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# File 'lib/sequel/dataset.rb', line 221

def inspect
  "#<#{self.class}: #{sql.inspect}>"
end

#intersect(dataset, all = false) ⇒ Object

Adds an INTERSECT clause using a second dataset object. If all is true the clause used is INTERSECT ALL, which may return duplicate rows.

DB[:items].intersect(DB[:other_items]).sql
#=> "SELECT * FROM items INTERSECT SELECT * FROM other_items"



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# File 'lib/sequel/dataset/sql.rb', line 329

def intersect(dataset, all = false)
  compound_clone(:intersect, dataset, all)
end

#interval(column) ⇒ Object

Returns the interval between minimum and maximum values for the given column.



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# File 'lib/sequel/dataset/convenience.rb', line 77

def interval(column)
  get{|o| o.max(column) - o.min(column)}
end

#invert ⇒ Object

Inverts the current filter

dataset.filter(:category => 'software').invert.sql #=>
  "SELECT * FROM items WHERE (category != 'software')"

Raises:



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# File 'lib/sequel/dataset/sql.rb', line 337

def invert
  having, where = @opts[:having], @opts[:where]
  raise(Error, "No current filter") unless having || where
  o = {}
  o[:having] = SQL::BooleanExpression.invert(having) if having
  o[:where] = SQL::BooleanExpression.invert(where) if where
  clone(o)
end

#irregular_function_sql(f) ⇒ Object

SQL fragment specifying an Irregular (cast/extract) SQL function call



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# File 'lib/sequel/dataset/sql.rb', line 347

def irregular_function_sql(f)
  "#{f.f}(#{literal(f.arg1)} #{f.joiner} #{literal(f.arg2)})"
end

#join_clause_sql(jc) ⇒ Object

SQL fragment specifying a JOIN clause without ON or USING.



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# File 'lib/sequel/dataset/sql.rb', line 352

def join_clause_sql(jc)
  table = jc.table
  table_alias = jc.table_alias
  table_alias = nil if table == table_alias
  tref = table_ref(table)
  " #{join_type_sql(jc.join_type)} #{table_alias ? as_sql(tref, table_alias) : tref}"
end

#join_on_clause_sql(jc) ⇒ Object

SQL fragment specifying a JOIN clause with ON.



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# File 'lib/sequel/dataset/sql.rb', line 361

def join_on_clause_sql(jc)
  "#{join_clause_sql(jc)} ON #{literal(filter_expr(jc.on))}"
end

#join_table(type, table, expr = nil, options = {}, &block) ⇒ Object

Returns a joined dataset. Uses the following arguments:

  • type - The type of join to do (:inner, :left_outer, :right_outer, :full)

  • table - Depends on type:

    • Dataset - a subselect is performed with an alias of tN for some value of N

    • Model (or anything responding to :table_name) - table.table_name

    • String, Symbol: table

  • expr - specifies conditions, depends on type:

    • Hash, Array with all two pairs - Assumes key (1st arg) is column of joined table (unless already qualified), and value (2nd arg) is column of the last joined or primary table (or the :implicit_qualifier option). To specify multiple conditions on a single joined table column, you must use an array. Uses a JOIN with an ON clause.

    • Array - If all members of the array are symbols, considers them as columns and uses a JOIN with a USING clause. Most databases will remove duplicate columns from the result set if this is used.

    • nil - If a block is not given, doesn’t use ON or USING, so the JOIN should be a NATURAL or CROSS join. If a block is given, uses a ON clause based on the block, see below.

    • Everything else - pretty much the same as a using the argument in a call to filter, so strings are considered literal, symbols specify boolean columns, and blockless filter expressions can be used. Uses a JOIN with an ON clause.

  • options - a hash of options, with any of the following keys:

    • :table_alias - the name of the table’s alias when joining, necessary for joining to the same table more than once. No alias is used by default.

    • :implicit_qualifer - The name to use for qualifying implicit conditions. By default, the last joined or primary table is used.

  • block - The block argument should only be given if a JOIN with an ON clause is used, in which case it yields the table alias/name for the table currently being joined, the table alias/name for the last joined (or first table), and an array of previous SQL::JoinClause.



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# File 'lib/sequel/dataset/sql.rb', line 400

def join_table(type, table, expr=nil, options={}, &block)
  if [Symbol, String].any?{|c| options.is_a?(c)}
    table_alias = options
    last_alias = nil 
  else
    table_alias = options[:table_alias]
    last_alias = options[:implicit_qualifier]
  end
  if Dataset === table
    if table_alias.nil?
      table_alias_num = (@opts[:num_dataset_sources] || 0) + 1
      table_alias = "t#{table_alias_num}"
    end
    table_name = table_alias
  else
    table = table.table_name if table.respond_to?(:table_name)
    table_name = table_alias || table
  end

  join = if expr.nil? and !block_given?
    SQL::JoinClause.new(type, table, table_alias)
  elsif Array === expr and !expr.empty? and expr.all?{|x| Symbol === x}
    raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block_given?
    SQL::JoinUsingClause.new(expr, type, table, table_alias)
  else
    last_alias ||= @opts[:last_joined_table] || (first_source.is_a?(Dataset) ? 't1' : first_source)
    if Hash === expr or (Array === expr and expr.all_two_pairs?)
      expr = expr.collect do |k, v|
        k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
        v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
        [k,v]
      end
    end
    if block_given?
      expr2 = yield(table_name, last_alias, @opts[:join] || [])
      expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
    end
    SQL::JoinOnClause.new(expr, type, table, table_alias)
  end

  opts = {:join => (@opts[:join] || []) + [join], :last_joined_table => table_name}
  opts[:num_dataset_sources] = table_alias_num if table_alias_num
  clone(opts)
end

#join_using_clause_sql(jc) ⇒ Object

SQL fragment specifying a JOIN clause with USING.



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# File 'lib/sequel/dataset/sql.rb', line 366

def join_using_clause_sql(jc)
  "#{join_clause_sql(jc)} USING (#{column_list(jc.using)})"
end

#last(*args, &block) ⇒ Object

Reverses the order and then runs first. Note that this will not necessarily give you the last record in the dataset, unless you have an unambiguous order. If there is not currently an order for this dataset, raises an Error.

Raises:



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# File 'lib/sequel/dataset/convenience.rb', line 85

def last(*args, &block)
  raise(Error, 'No order specified') unless @opts[:order]
  reverse.first(*args, &block)
end

#limit(l, o = nil) ⇒ Object

If given an integer, the dataset will contain only the first l results. If given a range, it will contain only those at offsets within that range. If a second argument is given, it is used as an offset.

Raises:



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# File 'lib/sequel/dataset/sql.rb', line 448

def limit(l, o = nil)
  return from_self.limit(l, o) if @opts[:sql]

  if Range === l
    o = l.first
    l = l.last - l.first + (l.exclude_end? ? 0 : 1)
  end
  l = l.to_i
  raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
  opts = {:limit => l}
  if o
    o = o.to_i
    raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
    opts[:offset] = o
  end
  clone(opts)
end

#literal(v) ⇒ Object

Returns a literal representation of a value to be used as part of an SQL expression.

dataset.literal("abc'def\\") #=> "'abc''def\\\\'"
dataset.literal(:items__id) #=> "items.id"
dataset.literal([1, 2, 3]) => "(1, 2, 3)"
dataset.literal(DB[:items]) => "(SELECT * FROM items)"
dataset.literal(:x + 1 > :y) => "((x + 1) > y)"

If an unsupported object is given, an exception is raised.



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# File 'lib/sequel/dataset/sql.rb', line 476

def literal(v)
  case v
  when String
    return v if v.is_a?(LiteralString)
    v.is_a?(SQL::Blob) ? literal_blob(v) : literal_string(v)
  when Symbol
    literal_symbol(v)
  when Integer
    literal_integer(v)
  when Hash
    literal_hash(v)
  when SQL::Expression
    literal_expression(v)
  when Float
    literal_float(v)
  when BigDecimal
    literal_big_decimal(v)
  when NilClass
    NULL
  when TrueClass
    literal_true
  when FalseClass
    literal_false
  when Array
    literal_array(v)
  when Time
    literal_time(v)
  when DateTime
    literal_datetime(v)
  when Date
    literal_date(v)
  when Dataset
    literal_dataset(v)
  else
    literal_other(v)
  end
end

#map(column_name = nil, &block) ⇒ Object

Maps column values for each record in the dataset (if a column name is given), or performs the stock mapping functionality of Enumerable.



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# File 'lib/sequel/dataset/convenience.rb', line 92

def map(column_name = nil, &block)
  if column_name
    super(){|r| r[column_name]}
  else
    super(&block)
  end
end

#max(column) ⇒ Object

Returns the maximum value for the given column.



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# File 'lib/sequel/dataset/convenience.rb', line 101

def max(column)
  get{|o| o.max(column)}
end

#min(column) ⇒ Object

Returns the minimum value for the given column.



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# File 'lib/sequel/dataset/convenience.rb', line 106

def min(column)
  get{|o| o.min(column)}
end

#model_classes ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 108

def model_classes
  Deprecation.deprecate('Sequel::Dataset#model_classes', 'Sequel::Model datasets no longer set this information')
  @opts[:models]
end

#multi_insert(*args) ⇒ Object

Inserts multiple records into the associated table. This method can be to efficiently insert a large amounts of records into a table. Inserts are automatically wrapped in a transaction.

This method should be called with a columns array and an array of value arrays:

dataset.multi_insert([:x, :y], [[1, 2], [3, 4]])

This method can also be called with an array of hashes:

dataset.multi_insert({:x => 1}, {:x => 2})

Be aware that all hashes should have the same keys if you use this calling method, otherwise some columns could be missed or set to null instead of to default values.

The method also accepts a :slice or :commit_every option that specifies the number of records to insert per transaction. This is useful especially when inserting a large number of records, e.g.:

# this will commit every 50 records
dataset.multi_insert(lots_of_records, :slice => 50)



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# File 'lib/sequel/dataset/convenience.rb', line 132

def multi_insert(*args)
  if args.empty?
    return
  elsif args[0].is_a?(Array) && args[1].is_a?(Array)
    columns, values, opts = *args
  elsif args[0].is_a?(Array) && args[1].is_a?(Dataset)
    table = @opts[:from].first
    columns, dataset = *args
    sql = "INSERT INTO #{quote_identifier(table)} (#{identifier_list(columns)}) VALUES #{literal(dataset)}"
    return @db.transaction{execute_dui(sql)}
  else
    # we assume that an array of hashes is given
    hashes, opts = *args
    return if hashes.empty?
    columns = hashes.first.keys
    # convert the hashes into arrays
    values = hashes.map {|h| columns.map {|c| h[c]}}
  end
  # make sure there's work to do
  return if columns.empty? || values.empty?
  
  slice_size = opts && (opts[:commit_every] || opts[:slice])
  
  if slice_size
    values.each_slice(slice_size) do |slice|
      statements = multi_insert_sql(columns, slice)
      @db.transaction(opts){statements.each{|st| execute_dui(st)}}
    end
  else
    statements = multi_insert_sql(columns, values)
    @db.transaction{statements.each{|st| execute_dui(st)}}
  end
end

#multi_insert_sql(columns, values) ⇒ Object

Returns an array of insert statements for inserting multiple records. This method is used by #multi_insert to format insert statements and expects a keys array and and an array of value arrays.

This method should be overridden by descendants if the support inserting multiple records in a single SQL statement.



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# File 'lib/sequel/dataset/sql.rb', line 520

def multi_insert_sql(columns, values)
  s = "INSERT INTO #{source_list(@opts[:from])} (#{identifier_list(columns)}) VALUES "
  values.map{|r| s + literal(r)}
end

#naked ⇒ Object

Returns a naked dataset clone - i.e. a dataset that returns records as hashes instead of calling the row proc.



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# File 'lib/sequel/dataset.rb', line 227

def naked
  ds = clone
  ds.row_proc = nil
  ds
end

#or(*cond, &block) ⇒ Object

Adds an alternate filter to an existing filter using OR. If no filter exists an error is raised.



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# File 'lib/sequel/dataset/sql.rb', line 527

def or(*cond, &block)
  clause = (@opts[:having] ? :having : :where)
  cond = cond.first if cond.size == 1
  if @opts[clause]
    clone(clause => SQL::BooleanExpression.new(:OR, @opts[clause], filter_expr(cond, &block)))
  else
    raise Error::NoExistingFilter, "No existing filter found."
  end
end

#order(*columns, &block) ⇒ Object Also known as: order_by

Returns a copy of the dataset with the order changed. If a nil is given the returned dataset has no order. This can accept multiple arguments of varying kinds, and even SQL functions.

ds.order(:name).sql #=> 'SELECT * FROM items ORDER BY name'
ds.order(:a, :b).sql #=> 'SELECT * FROM items ORDER BY a, b'
ds.order('a + b'.lit).sql #=> 'SELECT * FROM items ORDER BY a + b'
ds.order(:a + :b).sql #=> 'SELECT * FROM items ORDER BY (a + b)'
ds.order(:name.desc).sql #=> 'SELECT * FROM items ORDER BY name DESC'
ds.order(:name.asc).sql #=> 'SELECT * FROM items ORDER BY name ASC'
ds.order(:arr|1).sql #=> 'SELECT * FROM items ORDER BY arr[1]'
ds.order(nil).sql #=> 'SELECT * FROM items'



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# File 'lib/sequel/dataset/sql.rb', line 549

def order(*columns, &block)
  columns += Array(virtual_row_block_call(block)) if block
  clone(:order => (columns.compact.empty?) ? nil : columns)
end

#order_more(*columns, &block) ⇒ Object

Returns a copy of the dataset with the order columns added to the existing order.



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# File 'lib/sequel/dataset/sql.rb', line 557

def order_more(*columns, &block)
  order(*Array(@opts[:order]).concat(columns), &block)
end

#ordered_expression_sql(oe) ⇒ Object

SQL fragment for the ordered expression, used in the ORDER BY clause.



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# File 'lib/sequel/dataset/sql.rb', line 563

def ordered_expression_sql(oe)
  "#{literal(oe.expression)} #{oe.descending ? 'DESC' : 'ASC'}"
end

#paginate(page_no, page_size, record_count = nil) ⇒ Object

Returns a paginated dataset. The returned dataset is limited to the page size at the correct offset, and extended with the Pagination module. If a record count is not provided, does a count of total number of records for this dataset.

Raises:



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# File 'lib/sequel/extensions/pagination.rb', line 7

def paginate(page_no, page_size, record_count=nil)
  Sequel::Deprecation.deprecate('Sequel::Dataset#paginate', 'require "sequel/extensions/pagination" first')
  require "sequel/extensions/pagination"
  raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
  paginated = limit(page_size, (page_no - 1) * page_size)
  paginated.extend(Pagination)
  paginated.set_pagination_info(page_no, page_size, record_count || count)
end

#placeholder_literal_string_sql(pls) ⇒ Object

SQL fragment for a literal string with placeholders



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# File 'lib/sequel/dataset/sql.rb', line 568

def placeholder_literal_string_sql(pls)
  args = pls.args.dup
  s = pls.str.gsub(QUESTION_MARK){literal(args.shift)}
  s = "(#{s})" if pls.parens
  s
end

#polymorphic_key ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 113

def polymorphic_key
  Deprecation.deprecate('Sequel::Dataset#polymorphic_key', 'Sequel::Model datasets no longer set this information')
  @opts[:polymorphic_key]
end

#prepare(type, name = nil, values = nil) ⇒ Object

Prepare an SQL statement for later execution. This returns a clone of the dataset extended with PreparedStatementMethods, on which you can call call with the hash of bind variables to do substitution. The prepared statement is also stored in the associated database. The following usage is identical:

ps = prepare(:select, :select_by_name)
ps.call(:name=>'Blah')
db.call(:select_by_name, :name=>'Blah')



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# File 'lib/sequel/dataset/prepared_statements.rb', line 194

def prepare(type, name=nil, values=nil)
  ps = to_prepared_statement(type, values)
  db.prepared_statements[name] = ps if name
  ps
end

#print(*cols) ⇒ Object

Pretty prints the records in the dataset as plain-text table.



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# File 'lib/sequel/extensions/pretty_table.rb', line 4

def print(*cols)
  Sequel::Deprecation.deprecate('Sequel::Dataset#print', 'require "sequel/extensions/pretty_table" first')
  Sequel::PrettyTable.print(naked.all, cols.empty? ? columns : cols)
end

#qualified_identifier_sql(qcr) ⇒ Object

SQL fragment for the qualifed identifier, specifying a table and a column (or schema and table).



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# File 'lib/sequel/dataset/sql.rb', line 577

def qualified_identifier_sql(qcr)
  [qcr.table, qcr.column].map{|x| [SQL::QualifiedIdentifier, SQL::Identifier, Symbol].any?{|c| x.is_a?(c)} ? literal(x) : quote_identifier(x)}.join('.')
end

#query(&block) ⇒ Object

Translates a query block into a dataset. Query blocks can be useful when expressing complex SELECT statements, e.g.:

dataset = DB[:items].query do
  select :x, :y, :z
  filter{|o| (o.x > 1) & (o.y > 2)}
  order :z.desc
end

Which is the same as:

dataset = DB[:items].select(:x, :y, :z).filter{|o| (o.x > 1) & (o.y > 2)}.order(:z.desc)

Note that inside a call to query, you cannot call each, insert, update, or delete (or any method that calls those), or Sequel will raise an error.



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# File 'lib/sequel/extensions/query.rb', line 26

def query(&block)
  Sequel::Deprecation.deprecate('Sequel::Dataset#each_page', 'require "sequel/extensions/query" first')
  require "sequel/extensions/query"
  copy = clone({})
  copy.extend(QueryBlockCopy)
  copy.instance_eval(&block)
  clone(copy.opts)
end

#quote_column_ref(name) ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 185

def quote_column_ref(name)
  Sequel::Deprecation.deprecate('Sequel::Dataset#quote_column_ref', 'Use Sequel::Dataset#quote_identifier')
  quote_identifier(name)
end

#quote_identifier(name) ⇒ Object

Adds quoting to identifiers (columns and tables). If identifiers are not being quoted, returns name as a string. If identifiers are being quoted quote the name with quoted_identifier.



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# File 'lib/sequel/dataset/sql.rb', line 584

def quote_identifier(name)
  return name if name.is_a?(LiteralString)
  name = input_identifier(name)
  name = quoted_identifier(name) if quote_identifiers?
  name
end

#quote_identifiers? ⇒ Boolean

Whether this dataset quotes identifiers.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset.rb', line 234

def quote_identifiers?
  @quote_identifiers
end

#quote_schema_table(table) ⇒ Object

Separates the schema from the table and returns a string with them quoted (if quoting identifiers)



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# File 'lib/sequel/dataset/sql.rb', line 593

def quote_schema_table(table)
  schema, table = schema_and_table(table)
  "#{"#{quote_identifier(schema)}." if schema}#{quote_identifier(table)}"
end

#quoted_identifier(name) ⇒ Object

This method quotes the given name with the SQL standard double quote. should be overridden by subclasses to provide quoting not matching the SQL standard, such as backtick (used by MySQL and SQLite).



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# File 'lib/sequel/dataset/sql.rb', line 601

def quoted_identifier(name)
  "\"#{name.to_s.gsub('"', '""')}\""
end

#range(column) ⇒ Object

Returns a Range object made from the minimum and maximum values for the given column.



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# File 'lib/sequel/dataset/convenience.rb', line 168

def range(column)
  if r = select{|o| [o.min(column).as(:v1), o.max(column).as(:v2)]}.first
    (r[:v1]..r[:v2])
  end
end

#reverse_order(*order) ⇒ Object Also known as: reverse

Returns a copy of the dataset with the order reversed. If no order is given, the existing order is inverted.



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# File 'lib/sequel/dataset/sql.rb', line 607

def reverse_order(*order)
  order(*invert_order(order.empty? ? @opts[:order] : order))
end

#schema_and_table(table_name) ⇒ Object

Split the schema information from the table



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# File 'lib/sequel/dataset/sql.rb', line 613

def schema_and_table(table_name)
  sch = db.default_schema if db
  case table_name
  when Symbol
    s, t, a = split_symbol(table_name)
    [s||sch, t]
  when SQL::QualifiedIdentifier
    [table_name.table, table_name.column]
  when SQL::Identifier
    [sch, table_name.value]
  when String
    [sch, table_name]
  else
    raise Error, 'table_name should be a Symbol, SQL::QualifiedIdentifier, SQL::Identifier, or String'
  end
end

#select(*columns, &block) ⇒ Object

Returns a copy of the dataset with the columns selected changed to the given columns.



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# File 'lib/sequel/dataset/sql.rb', line 632

def select(*columns, &block)
  columns += Array(virtual_row_block_call(block)) if block
  clone(:select => columns)
end

#select_all ⇒ Object

Returns a copy of the dataset selecting the wildcard.



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# File 'lib/sequel/dataset/sql.rb', line 638

def select_all
  clone(:select => nil)
end

#select_more(*columns, &block) ⇒ Object

Returns a copy of the dataset with the given columns added to the existing selected columns.



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# File 'lib/sequel/dataset/sql.rb', line 644

def select_more(*columns, &block)
  select(*Array(@opts[:select]).concat(columns), &block)
end

#select_sql(opts = (defarg=true;nil)) ⇒ Object

Formats a SELECT statement using the given options and the dataset options.



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# File 'lib/sequel/dataset/sql.rb', line 650

def select_sql(opts = (defarg=true;nil))
  Deprecation.deprecate("Calling Dataset#select_sql with an argument is deprecated and will raise an error in a future version.  Use dataset.clone(opts).select_sql.") unless defarg
  opts = opts ? @opts.merge(opts) : @opts
  return static_sql(opts[:sql]) if opts[:sql]
  sql = 'SELECT'
  select_clause_order.each{|x| send("select_#{x}_sql", sql, opts)}
  sql
end

#server(servr) ⇒ Object

Set the server for this dataset to use. Used to pick a specific database shard to run a query against, or to override the default SELECT uses :read_only database and all other queries use the :default database.



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# File 'lib/sequel/dataset.rb', line 241

def server(servr)
  clone(:server=>servr)
end

#set(*args) ⇒ Object

Alias for set, but not aliased directly so subclasses don’t have to override both methods.



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# File 'lib/sequel/dataset.rb', line 247

def set(*args)
  update(*args)
end

#set_defaults(hash) ⇒ Object

Set the default values for insert and update statements. The values passed to insert or update are merged into this hash.



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# File 'lib/sequel/dataset.rb', line 253

def set_defaults(hash)
  clone(:defaults=>(@opts[:defaults]||{}).merge(hash))
end

#set_graph_aliases(graph_aliases) ⇒ Object

This allows you to manually specify the graph aliases to use when using graph. You can use it to only select certain columns, and have those columns mapped to specific aliases in the result set. This is the equivalent of .select for a graphed dataset, and must be used instead of .select whenever graphing is used. Example:

DB[:artists].graph(:albums, :artist_id=>:id).set_graph_aliases(:artist_name=>[:artists, :name], :album_name=>[:albums, :name]).first
=> {:artists=>{:name=>artists.name}, :albums=>{:name=>albums.name}}

Arguments:

  • graph_aliases - Should be a hash with keys being symbols of column aliases, and values being arrays with two symbol elements. The first element of the array should be the table alias, and the second should be the actual column name.



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# File 'lib/sequel/object_graph.rb', line 158

def set_graph_aliases(graph_aliases)
  ds = select(*graph_alias_columns(graph_aliases))
  ds.opts[:graph_aliases] = graph_aliases
  ds
end

#set_model(key, *args) ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 118

def set_model(key, *args)
  Deprecation.deprecate('Sequel::Dataset#set_model', 'Use Sequel::Dataset#set_row_proc with an appropriate row proc')
  # This code is more verbose then necessary for performance reasons
  case key
  when nil # set_model(nil) => no argument provided, so the dataset is denuded
    @opts.merge!(:naked => true, :models => nil, :polymorphic_key => nil)
    self.row_proc = nil
  when Class
    # isomorphic model
    @opts.merge!(:naked => nil, :models => {nil => key}, :polymorphic_key => nil)
    if key.respond_to?(:load)
      # the class has a values setter method, so we use it
      self.row_proc = proc{|h| key.load(h, *args)}
    else
      # otherwise we just pass the hash to the constructor
      self.row_proc = proc{|h| key.new(h, *args)}
    end
  when Symbol
    # polymorphic model
    hash = args.shift || raise(ArgumentError, "No class hash supplied for polymorphic model")
    @opts.merge!(:naked => true, :models => hash, :polymorphic_key => key)
    if (hash.empty? ? (hash[nil] rescue nil) : hash.values.first).respond_to?(:load)
      # the class has a values setter method, so we use it
      self.row_proc = proc do |h|
        c = hash[h[key]] || hash[nil] || \
          raise(Error, "No matching model class for record (#{polymorphic_key} => #{h[polymorphic_key].inspect})")
        c.load(h, *args)
      end
    else
      # otherwise we just pass the hash to the constructor
      self.row_proc = proc do |h|
        c = hash[h[key]] || hash[nil] || \
          raise(Error, "No matching model class for record (#{polymorphic_key} => #{h[polymorphic_key].inspect})")
        c.new(h, *args)
      end
    end
  else
    raise ArgumentError, "Invalid model specified"
  end
  self
end

#set_overrides(hash) ⇒ Object

Set values that override hash arguments given to insert and update statements. This hash is merged into the hash provided to insert or update.



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# File 'lib/sequel/dataset.rb', line 259

def set_overrides(hash)
  clone(:overrides=>hash.merge(@opts[:overrides]||{}))
end

#single_record(opts = (defarg=true;nil)) ⇒ Object

Returns the first record in the dataset.



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# File 'lib/sequel/dataset/convenience.rb', line 175

def single_record(opts = (defarg=true;nil))
  Deprecation.deprecate("Calling Dataset#single_record with an argument is deprecated and will raise an error in a future version.  Use dataset.clone(opts).single_record.") unless defarg
  ds = clone(:limit=>1)
  opts = opts.merge(:limit=>1) if opts and opts[:limit]
  defarg ? ds.each{|r| return r} : ds.each(opts){|r| return r}
  nil
end

#single_value(opts = (defarg=true;nil)) ⇒ Object

Returns the first value of the first record in the dataset. Returns nil if dataset is empty.



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# File 'lib/sequel/dataset/convenience.rb', line 185

def single_value(opts = (defarg=true;nil))
  Deprecation.deprecate("Calling Dataset#single_value with an argument is deprecated and will raise an error in a future version.  Use dataset.clone(opts).single_value.") unless defarg
  ds = naked.clone(:graph=>false)
  if r = (defarg ? ds.single_record : ds.single_record(opts))
    r.values.first
  end
end

#size ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 175

def size
  Sequel::Deprecation.deprecate('Sequel::Dataset#size', 'Use Sequel::Dataset#count')
  count
end

#sql(opts = (defarg=true;nil)) ⇒ Object

Same as select_sql, not aliased directly to make subclassing simpler.



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# File 'lib/sequel/dataset/sql.rb', line 660

def sql(opts = (defarg=true;nil))
  Deprecation.deprecate("Calling Dataset#select_sql with an argument is deprecated and will raise an error in a future version.  Use dataset.clone(opts).select_sql.") unless defarg
  defarg ? select_sql : select_sql(opts)
end

#subscript_sql(s) ⇒ Object

SQL fragment for specifying subscripts (SQL arrays)



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# File 'lib/sequel/dataset/sql.rb', line 666

def subscript_sql(s)
  "#{s.f}[#{s.sub.join(COMMA_SEPARATOR)}]"
end

#sum(column) ⇒ Object

Returns the sum for the given column.



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# File 'lib/sequel/dataset/convenience.rb', line 194

def sum(column)
  get{|o| o.sum(column)}
end

#symbol_to_column_ref(sym) ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 190

def symbol_to_column_ref(sym)
  Sequel::Deprecation.deprecate('Sequel::Dataset#symbol_to_column_ref', 'Use Sequel::Dataset#literal')
  literal_symbol(sym)
end

#table_exists? ⇒ Boolean

Returns true if the table exists. Will raise an error if the dataset has fixed SQL or selects from another dataset or more than one table.

Returns:

  • (Boolean)

Raises:



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# File 'lib/sequel/dataset/convenience.rb', line 201

def table_exists?
  raise(Sequel::Error, "this dataset has fixed SQL") if @opts[:sql]
  raise(Sequel::Error, "this dataset selects from multiple sources") if @opts[:from].size != 1
  t = @opts[:from].first
  raise(Sequel::Error, "this dataset selects from a sub query") if t.is_a?(Dataset)
  @db.table_exists?(t)
end

#to_csv(include_column_titles = true) ⇒ Object

Returns a string in CSV format containing the dataset records. By default the CSV representation includes the column titles in the first line. You can turn that off by passing false as the include_column_titles argument.

This does not use a CSV library or handle quoting of values in any way. If any values in any of the rows could include commas or line endings, you probably shouldn’t use this.



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# File 'lib/sequel/dataset/convenience.rb', line 217

def to_csv(include_column_titles = true)
  n = naked
  cols = n.columns
  csv = ''
  csv << "#{cols.join(COMMA_SEPARATOR)}\r\n" if include_column_titles
  n.each{|r| csv << "#{cols.collect{|c| r[c]}.join(COMMA_SEPARATOR)}\r\n"}
  csv
end

#to_hash(key_column, value_column = nil) ⇒ Object

Returns a hash with one column used as key and another used as value. If rows have duplicate values for the key column, the latter row(s) will overwrite the value of the previous row(s). If the value_column is not given or nil, uses the entire hash as the value.



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# File 'lib/sequel/dataset/convenience.rb', line 230

def to_hash(key_column, value_column = nil)
  inject({}) do |m, r|
    m[r[key_column]] = value_column ? r[value_column] : r
    m
  end
end

#transform(t) ⇒ Object

Sets a value transform which is used to convert values loaded and saved to/from the database. The transform should be supplied as a hash. Each value in the hash should be an array containing two proc objects - one for transforming loaded values, and one for transforming saved values. The following example demonstrates how to store Ruby objects in a dataset using Marshal serialization:

dataset.transform(:obj => [
  proc {|v| Marshal.load(v)},
  proc {|v| Marshal.dump(v)}
])

dataset.insert_sql(:obj => 1234) #=>
"INSERT INTO items (obj) VALUES ('\004\bi\002\322\004')"

Another form of using transform is by specifying stock transforms:

dataset.transform(:obj => :marshal)

The currently supported stock transforms are :marshal and :yaml.



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# File 'lib/sequel/dataset.rb', line 283

def transform(t)
  @transform = t
  t.each do |k, v|
    case v
    when Array
      if (v.size != 2) || !v.first.is_a?(Proc) && !v.last.is_a?(Proc)
        raise Error::InvalidTransform, "Invalid transform specified"
      end
    else
      unless v = STOCK_TRANSFORMS[v]
        raise Error::InvalidTransform, "Invalid transform specified"
      else
        t[k] = v
      end
    end
  end
  self
end

#transform_load(r) ⇒ Object

Applies the value transform for data loaded from the database.



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# File 'lib/sequel/dataset.rb', line 303

def transform_load(r)
  r.inject({}) do |m, kv|
    k, v = *kv
    m[k] = (tt = @transform[k]) ? tt[0][v] : v
    m
  end
end

#transform_save(r) ⇒ Object

Applies the value transform for data saved to the database.



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# File 'lib/sequel/dataset.rb', line 312

def transform_save(r)
  r.inject({}) do |m, kv|
    k, v = *kv
    m[k] = (tt = @transform[k]) ? tt[1][v] : v
    m
  end
end

#unfiltered ⇒ Object

Returns a copy of the dataset with no filters (HAVING or WHERE clause) applied.



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# File 'lib/sequel/dataset/sql.rb', line 671

def unfiltered
  clone(:where => nil, :having => nil)
end

#union(dataset, all = false) ⇒ Object

Adds a UNION clause using a second dataset object. If all is true the clause used is UNION ALL, which may return duplicate rows.

DB[:items].union(DB[:other_items]).sql
#=> "SELECT * FROM items UNION SELECT * FROM other_items"



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# File 'lib/sequel/dataset/sql.rb', line 680

def union(dataset, all = false)
  compound_clone(:union, dataset, all)
end

#uniq(*args) ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 180

def uniq(*args)
  Sequel::Deprecation.deprecate('Sequel::Dataset#uniq', 'Use Sequel::Dataset#distinct')
  distinct(*args)
end

#unordered ⇒ Object

Returns a copy of the dataset with no order.



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# File 'lib/sequel/dataset/sql.rb', line 685

def unordered
  order(nil)
end

#upcase_identifiers=(v) ⇒ Object 



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# File 'lib/sequel/deprecated.rb', line 98

def upcase_identifiers=(v)
  Deprecation.deprecate('Sequel::Dataset#upcase_identifiers=', 'Use Sequel::Dataset#identifier_input_method = :upcase or nil')
  @identifier_input_method = v ? :upcase : nil
end

#upcase_identifiers? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/sequel/deprecated.rb', line 103

def upcase_identifiers?
  Deprecation.deprecate('Sequel::Dataset#upcase_identifiers?', 'Use Sequel::Dataset#identifier_input_method == :upcase')
  @identifier_input_method == :upcase
end

#update(values = {}, opts = (defarg=true;nil)) ⇒ Object

Updates values for the dataset. The returned value is generally the number of rows updated, but that is adapter dependent.



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# File 'lib/sequel/dataset.rb', line 322

def update(values={}, opts=(defarg=true;nil))
  Deprecation.deprecate("Calling Dataset#update with an argument is deprecated and will raise an error in a future version.  Use dataset.clone(opts).update.") unless defarg
  execute_dui(defarg ? update_sql(values) : update_sql(value, opts))
end

#update_sql(values = {}, opts = (defarg=true;nil)) ⇒ Object

Formats an UPDATE statement using the given values.

dataset.update_sql(:price => 100, :category => 'software') #=>
  "UPDATE items SET price = 100, category = 'software'"

Accepts a block, but such usage is discouraged.

Raises an error if the dataset is grouped or includes more than one table.



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# File 'lib/sequel/dataset/sql.rb', line 698

def update_sql(values = {}, opts = (defarg=true;nil))
  Deprecation.deprecate("Calling Dataset#update_sql with an argument is deprecated and will raise an error in a future version.  Use dataset.clone(opts).update_sql.") unless defarg
  opts = opts ? @opts.merge(opts) : @opts

  return static_sql(opts[:sql]) if opts[:sql]

  if opts[:group]
    raise Error::InvalidOperation, "A grouped dataset cannot be updated"
  elsif (opts[:from].size > 1) or opts[:join]
    raise Error::InvalidOperation, "A joined dataset cannot be updated"
  end
  
  sql = "UPDATE #{source_list(@opts[:from])} SET "
  set = if values.is_a?(Hash)
    values = opts[:defaults].merge(values) if opts[:defaults]
    values = values.merge(opts[:overrides]) if opts[:overrides]
    # get values from hash
    values = transform_save(values) if @transform
    values.map do |k, v|
      "#{[String, Symbol].any?{|c| k.is_a?(c)} ? quote_identifier(k) : literal(k)} = #{literal(v)}"
    end.join(COMMA_SEPARATOR)
  else
    # copy values verbatim
    values
  end
  sql << set
  if where = opts[:where]
    sql << " WHERE #{literal(where)}"
  end

  sql
end

#where(*cond, &block) ⇒ Object

Add a condition to the WHERE clause. See #filter for argument types.



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# File 'lib/sequel/dataset/sql.rb', line 732

def where(*cond, &block)
  _filter(:where, *cond, &block)
end

#with_sql(sql, *args) ⇒ Object

Returns a copy of the dataset with the static SQL used. This is useful if you want to keep the same row_proc/transform/graph, but change the SQL used to custom SQL.



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# File 'lib/sequel/dataset/sql.rb', line 738

def with_sql(sql, *args)
  sql = SQL::PlaceholderLiteralString.new(sql, args) unless args.empty?
  clone(:sql=>sql)
end