Class: Sequel::Dataset

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

Overview

A dataset represents an SQL query, or more generally, an abstract set of rows in the database. 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 (datasets never cache results):

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

Most dataset methods return modified copies of the dataset (functional style), so you can reuse different datasets to access data:

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

Constant Summary

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 except exclude
filter from from_self full_outer_join graph
group group_and_count group_by having inner_join intersect invert join join_table
left_outer_join limit naked or order order_by order_more paginate qualify query
reverse reverse_order right_outer_join select select_all select_more server
set_defaults set_graph_aliases set_overrides unfiltered ungraphed ungrouped union
unlimited unordered where with with_recursive with_sql'.collect{|x| x.to_sym}
NOTIMPL_MSG =
"This method must be overridden in Sequel adapters".freeze
WITH_SUPPORTED =
:select_with_sql
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]
DATASET_ALIAS_BASE_NAME =
't'.freeze
FROM_SELF_KEEP_OPTS =
[:graph, :eager_graph, :graph_aliases]
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
QUALIFY_KEYS =
[:select, :where, :having, :order, :group]
QUESTION_MARK =
'?'.freeze
STOCK_COUNT_OPTS =
{:select => [SQL::AliasedExpression.new(LiteralString.new("COUNT(*)").freeze, :count)], :order => nil}.freeze
DELETE_CLAUSE_METHODS =
clause_methods(:delete, %w'from where')
INSERT_CLAUSE_METHODS =
clause_methods(:insert, %w'into columns values')
SELECT_CLAUSE_METHODS =
clause_methods(:select, %w'with distinct columns from join where group having compounds order limit')
UPDATE_CLAUSE_METHODS =
clause_methods(:update, %w'table set where')
TIMESTAMP_FORMAT =
"'%Y-%m-%d %H:%M:%S%N%z'".freeze
STANDARD_TIMESTAMP_FORMAT =
"TIMESTAMP #{TIMESTAMP_FORMAT}".freeze
TWO_ARITY_OPERATORS =
::Sequel::SQL::ComplexExpression::TWO_ARITY_OPERATORS
WILDCARD =
'*'.freeze
SQL_WITH =
"WITH ".freeze
COMMA_SEPARATOR =
', '.freeze
COUNT_OF_ALL_AS_COUNT =
SQL::Function.new(:count, LiteralString.new('*'.freeze)).as(:count)
ARRAY_ACCESS_ERROR_MSG =
'You cannot call Dataset#[] with an integer or with no arguments.'.freeze
MAP_ERROR_MSG =
'Using Dataset#map with an argument and a block is not allowed'.freeze
GET_ERROR_MSG =
'must provide argument or block to Dataset#get, not both'.freeze
IMPORT_ERROR_MSG =
'Using Sequel::Dataset#import an empty column array is not allowed'.freeze
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

#fourth, #second, #third

Constructor Details

#initialize(db, opts = nil) ⇒ Dataset

Constructs a new Dataset instance with an associated database and options. Datasets are usually constructed by invoking the Database#[] method:

DB[:posts]

Sequel::Dataset is an abstract class that is not useful by itself. Each database adaptor should provide a subclass of Sequel::Dataset, and have the Database#dataset method return an instance of that class.



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# File 'lib/sequel/lib/sequel/dataset.rb', line 84

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
end

Instance Attribute Details

#dbObject

The database that corresponds to this dataset



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# File 'lib/sequel/lib/sequel/dataset.rb', line 57

def db
  @db
end

#identifier_input_methodObject

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



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# File 'lib/sequel/lib/sequel/dataset.rb', line 60

def identifier_input_method
  @identifier_input_method
end

#identifier_output_methodObject

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



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# File 'lib/sequel/lib/sequel/dataset.rb', line 63

def identifier_output_method
  @identifier_output_method
end

#optsObject

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



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# File 'lib/sequel/lib/sequel/dataset.rb', line 66

def opts
  @opts
end

#quote_identifiers=(value) ⇒ Object (writeonly)

Whether to quote identifiers for this dataset



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# File 'lib/sequel/lib/sequel/dataset.rb', line 69

def quote_identifiers=(value)
  @quote_identifiers = value
end

#row_procObject

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



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

def row_proc
  @row_proc
end

Class Method Details

.clause_methods(type, clauses) ⇒ Object

Given a type (e.g. select) and an array of clauses, return an array of methods to call to build the SQL string.



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 6

def self.clause_methods(type, clauses)
  clauses.map{|clause| :#{type}_#{clause}_sql"}.freeze
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/lib/sequel/dataset.rb', line 98

def self.def_mutation_method(*meths)
  meths.each do |meth|
    class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end", __FILE__, __LINE__)
  end
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/lib/sequel/dataset.rb', line 108

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

#[](*conditions) ⇒ Object

Returns the first record matching the conditions. Examples:

ds[:id=>1] => {:id=1}

Raises:



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# File 'lib/sequel/lib/sequel/dataset/convenience.rb', line 13

def [](*conditions)
  raise(Error, ARRAY_ACCESS_ERROR_MSG) if (conditions.length == 1 and conditions.first.is_a?(Integer)) or conditions.length == 0
  first(*conditions)
end

#[]=(conditions, values) ⇒ Object

Update all records matching the conditions with the values specified. Examples:

ds[:id=>1] = {:id=>2} # SQL: UPDATE ... SET id = 2 WHERE id = 1


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# File 'lib/sequel/lib/sequel/dataset/convenience.rb', line 22

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

#add_graph_aliases(graph_aliases) ⇒ Object

Adds the given 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/lib/sequel/dataset/graph.rb', line 6

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

#aliased_expression_sql(ae) ⇒ Object

SQL fragment for the aliased expression



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 47

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

#all(&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/lib/sequel/dataset.rb', line 121

def all(&block)
  a = []
  each{|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.

ds.filter(:a).and(:b) # SQL: WHERE a AND b

Raises:



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 41

def and(*cond, &block)
  raise(InvalidOperation, "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/lib/sequel/dataset/sql.rb', line 52

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

#as(aliaz) ⇒ Object

Return the dataset as an aliased expression with the given alias. You can use this as a FROM or JOIN dataset, or as a column if this dataset returns a single row and column.



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# File 'lib/sequel/lib/sequel/dataset.rb', line 115

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/lib/sequel/dataset/convenience.rb', line 27

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/lib/sequel/dataset/prepared_statements.rb', line 176

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/lib/sequel/dataset/sql.rb', line 57

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/lib/sequel/dataset/sql.rb', line 67

def cast_sql(expr, type)
  "CAST(#{literal(expr)} AS #{db.cast_type_literal(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/lib/sequel/dataset.rb', line 132

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/lib/sequel/dataset/sql.rb', line 72

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

#columnsObject

Returns the columns in the result set in 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 may be an empty array depending on how the adapter is programmed.

If you are looking for all columns for a single table and maybe some information about each column (e.g. type), see Database#schema.



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# File 'lib/sequel/lib/sequel/dataset.rb', line 148

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/lib/sequel/dataset.rb', line 158

def columns!
  @columns = nil
  columns
end

#complex_expression_sql(op, args) ⇒ Object

SQL fragment for complex expressions



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

def complex_expression_sql(op, args)
  case op
  when *IS_OPERATORS
    r = args.at(1)
    if r.nil? || supports_is_true?
      raise(InvalidOperation, 'Invalid argument used for IS operator') unless v = IS_LITERALS[r]
      "(#{literal(args.at(0))} #{op} #{v})"
    elsif op == :IS
      complex_expression_sql(:=", args)
    else
      complex_expression_sql(:OR, [SQL::BooleanExpression.new(:!=", *args), SQL::BooleanExpression.new(:IS, args.at(0), nil)])
    end
  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(InvalidOperation, "invalid operator #{op}")
  end
end

#constant_sql(constant) ⇒ Object

SQL fragment for constants



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 105

def constant_sql(constant)
  constant.to_s
end

#countObject

Returns the number of records in the dataset.



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 110

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

#def_mutation_method(*meths) ⇒ Object

Add a mutation method to this dataset instance.



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# File 'lib/sequel/lib/sequel/dataset.rb', line 164

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

#deleteObject

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



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# File 'lib/sequel/lib/sequel/dataset.rb', line 172

def delete
  execute_dui(delete_sql)
end

#delete_sqlObject

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/lib/sequel/dataset/sql.rb', line 118

def delete_sql
  return static_sql(opts[:sql]) if opts[:sql]
  check_modification_allowed!
  clause_sql(:delete)
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. Raises an error if arguments are given and DISTINCT ON is not supported.

dataset.distinct # SQL: SELECT DISTINCT * FROM items
dataset.order(:id).distinct(:id) # SQL: SELECT DISTINCT ON (id) * FROM items ORDER BY id

Raises:



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 133

def distinct(*args)
  raise(InvalidOperation, "DISTINCT ON not supported") if !args.empty? && !supports_distinct_on?
  clone(:distinct => args)
end

#each(&block) ⇒ Object

Iterates over the records in the dataset as they are yielded from the database adapter, and returns self.

Note that this method is not safe to use on many adapters if you are running additional queries inside the provided block. If you are running queries inside the block, you use should all instead of each.



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# File 'lib/sequel/lib/sequel/dataset.rb', line 182

def each(&block)
  if @opts[:graph]
    graph_each(&block)
  else
    if row_proc = @row_proc
      fetch_rows(select_sql){|r| yield row_proc.call(r)}
    else
      fetch_rows(select_sql, &block)
    end
  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/lib/sequel/extensions/pagination.rb', line 20

def each_page(page_size, &block)
  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 exist in the dataset, false otherwise

Returns:

  • (Boolean)


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# File 'lib/sequel/lib/sequel/dataset/convenience.rb', line 32

def empty?
  get(1).nil?
end

#except(dataset, opts = {}) ⇒ Object

Adds an EXCEPT clause using a second dataset object. An EXCEPT compound dataset returns all rows in the current dataset that are not in the given dataset. Raises an InvalidOperation if the operation is not supported. Options:

  • :all - Set to true to use EXCEPT ALL instead of EXCEPT, so duplicate rows can occur

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

    DB.except(DB).sql #=> “SELECT * FROM items EXCEPT SELECT * FROM other_items”

Raises:



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 148

def except(dataset, opts={})
  opts = {:all=>opts} unless opts.is_a?(Hash)
  raise(InvalidOperation, "EXCEPT not supported") unless supports_intersect_except?
  raise(InvalidOperation, "EXCEPT ALL not supported") if opts[:all] && !supports_intersect_except_all?
  compound_clone(:except, dataset, opts)
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/lib/sequel/dataset/sql.rb', line 159

def exclude(*cond, &block)
  clause = (@opts[:having] ? :having : :where)
  cond = cond.first if cond.size == 1
  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

#existsObject

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/lib/sequel/dataset/sql.rb', line 172

def exists
  LiteralString.new("EXISTS (#{select_sql})")
end

#fetch_rows(sql, &block) ⇒ Object

Executes a select query and fetches records, passing each record to the supplied block. The yielded records should be hashes with symbol keys.

Raises:

  • (NotImplementedError)


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# File 'lib/sequel/lib/sequel/dataset.rb', line 197

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. This block yields a virtual row object, which is easy to use to create identifiers and functions.

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/lib/sequel/dataset/sql.rb', line 223

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

#first(*args, &block) ⇒ Object

If a integer 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/lib/sequel/dataset/convenience.rb', line 55

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_aliasObject Also known as: first_source

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/lib/sequel/dataset/sql.rb', line 229

def first_source_alias
  source = @opts[:from]
  if source.nil? || source.empty?
    raise Error, 'No source specified for query'
  end
  case s = source.first
  when SQL::AliasedExpression
    s.aliaz
  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.

dataset.from # SQL: SELECT *
dataset.from(:blah) # SQL: SELECT * FROM blah
dataset.from(:blah, :foo) # SQL: SELECT * FROM blah, foo


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 251

def from(*source)
  table_alias_num = 0
  sources = []
  source.each do |s|
    case s
    when Hash
      s.each{|k,v| sources << SQL::AliasedExpression.new(k,v)}
    when Dataset
      sources << SQL::AliasedExpression.new(s, dataset_alias(table_alias_num+=1))
    when Symbol
      sch, table, aliaz = split_symbol(s)
      if aliaz
        s = sch ? SQL::QualifiedIdentifier.new(sch.to_sym, table.to_sym) : SQL::Identifier.new(table.to_sym)
        sources << SQL::AliasedExpression.new(s, aliaz.to_sym)
      else
        sources << s
      end
    else
      sources << s
    end
  end
  o = {:from=>sources.empty? ? nil : sources}
  o[:num_dataset_sources] = table_alias_num if table_alias_num > 0
  clone(o)
end

#from_self(opts = {}) ⇒ Object

Returns a dataset selecting from the current dataset. Supplying the :alias option controls the name of the result.

ds = DB[:items].order(:name).select(:id, :name)
ds.sql                         #=> "SELECT id,name FROM items ORDER BY name"
ds.from_self.sql               #=> "SELECT * FROM (SELECT id, name FROM items ORDER BY name) AS 't1'"
ds.from_self(:alias=>:foo).sql #=> "SELECT * FROM (SELECT id, name FROM items ORDER BY name) AS 'foo'"


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 284

def from_self(opts={})
  fs = {}
  @opts.keys.each{|k| fs[k] = nil unless FROM_SELF_KEEP_OPTS.include?(k)}
  clone(fs).from(opts[:alias] ? as(opts[:alias]) : self)
end

#function_sql(f) ⇒ Object

SQL fragment specifying an SQL function call



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 291

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 an error if both an argument and block is given.

ds.get(:id)
ds.get{|o| o.sum(:id)}


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# File 'lib/sequel/lib/sequel/dataset/convenience.rb', line 75

def get(column=nil, &block)
  if column
    raise(Error, GET_ERROR_MSG) if block
    select(column).single_value
  else
    select(&block).single_value
  end
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, :name=>albums.name, :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 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 return 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:

    • :from_self_alias - The alias to use when the receiver is not a graphed dataset but it contains multiple FROM tables or a JOIN. In this case, the receiver is wrapped in a from_self before graphing, and this option determines the alias to use.

    • :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/lib/sequel/dataset/graph.rb', line 60

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)
  table_alias = options[:table_alias]
  case dataset
  when Symbol
    table = dataset
    dataset = @db[dataset]
    table_alias ||= table
  when ::Sequel::Dataset
    if dataset.simple_select_all?
      table = dataset.opts[:from].first
      table_alias ||= table
    else
      table = dataset
      table_alias ||= dataset_alias((@opts[:num_dataset_sources] || 0)+1)
    end
  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
  raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)
  
  # Use a from_self if this is already a joined table
  ds = (!@opts[:graph] && (@opts[:from].length > 1 || @opts[:join])) ? from_self(:alias=>options[:from_self_alias] || first_source) : self
  
  # Join the table early in order to avoid cloning the dataset twice
  ds = 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_alias
    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(SQL::QualifiedIdentifier.new(master, column))
      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, SQL::QualifiedIdentifier.new(table_alias, column).as(column_alias)]
      else
        [column, SQL::QualifiedIdentifier.new(table_alias, column)]
      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.

dataset.grep(:a, '%test%') # SQL: SELECT * FROM items WHERE a LIKE '%test%'
dataset.grep([:a, :b], %w'%test% foo') # SQL: SELECT * FROM items WHERE a LIKE '%test%' OR a LIKE 'foo' OR b LIKE '%test%' OR b LIKE 'foo'


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 304

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.

dataset.group(:id) # SELECT * FROM items GROUP BY id
dataset.group(:id, :name) # SELECT * FROM items GROUP BY id, name


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 313

def group(*columns)
  clone(:group => (columns.compact.empty? ? nil : columns))
end

#group_and_count(*columns) ⇒ Object

Returns a dataset grouped by the given column with count by group, order by the count of records. Examples:

ds.group_and_count(:name) => [{:name=>'a', :count=>1}, ...]
ds.group_and_count(:first_name, :last_name) => [{:first_name=>'a', :last_name=>'b', :count=>1}, ...]


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# File 'lib/sequel/lib/sequel/dataset/convenience.rb', line 89

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.

dataset.group(:sum).having(:sum=>10) # SQL: SELECT * FROM items GROUP BY sum HAVING sum = 10

Raises:



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

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

#import(columns, values, opts = {}) ⇒ 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 is called with a columns array and an array of value arrays:

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

This method also accepts a dataset instead of an array of value arrays:

dataset.import([:x, :y], other_dataset.select(:a___x, :b___y))

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.import([:x, :y], [[1, 2], [3, 4], ...], :slice => 50)

Raises:



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# File 'lib/sequel/lib/sequel/dataset/convenience.rb', line 111

def import(columns, values, opts={})
  return @db.transaction{insert(columns, values)} if values.is_a?(Dataset)

  return if values.empty?
  raise(Error, IMPORT_ERROR_MSG) if columns.empty?
  
  if slice_size = opts[:commit_every] || opts[:slice]
    offset = 0
    loop do
      @db.transaction(opts){multi_insert_sql(columns, values[offset, slice_size]).each{|st| execute_dui(st)}}
      offset += slice_size
      break if offset >= values.length
    end
  else
    statements = multi_insert_sql(columns, values)
    @db.transaction{statements.each{|st| execute_dui(st)}}
  end
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. See insert_sql.



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# File 'lib/sequel/lib/sequel/dataset.rb', line 204

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/lib/sequel/dataset/sql.rb', line 331

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. The API is a little complex, and best explained by example:

# Default values
DB[:items].insert_sql #=> 'INSERT INTO items DEFAULT VALUES'
DB[:items].insert_sql({}) #=> 'INSERT INTO items DEFAULT VALUES'
# Values without columns
DB[:items].insert_sql(1,2,3) #=> 'INSERT INTO items VALUES (1, 2, 3)'
DB[:items].insert_sql([1,2,3]) #=> 'INSERT INTO items VALUES (1, 2, 3)'
# Values with columns
DB[:items].insert_sql([:a, :b], [1,2]) #=> 'INSERT INTO items (a, b) VALUES (1, 2)'
DB[:items].insert_sql(:a => 1, :b => 2) #=> 'INSERT INTO items (a, b) VALUES (1, 2)'
# Using a subselect
DB[:items].insert_sql(DB[:old_items]) #=> 'INSERT INTO items SELECT * FROM old_items
# Using a subselect with columns
DB[:items].insert_sql([:a, :b], DB[:old_items]) #=> 'INSERT INTO items (a, b) SELECT * FROM old_items


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 355

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

  check_modification_allowed!

  columns = []

  case values.size
  when 0
    return insert_sql({})
  when 1
    case vals = values.at(0)
    when Hash
      vals = @opts[:defaults].merge(vals) if @opts[:defaults]
      vals = vals.merge(@opts[:overrides]) if @opts[:overrides]
      values = []
      vals.each do |k,v| 
        columns << k
        values << v
      end
    when Dataset, Array, LiteralString
      values = vals
    else
      if vals.respond_to?(:values) && (v = vals.values).is_a?(Hash)
        return insert_sql(v) 
      end
    end
  when 2
    if (v0 = values.at(0)).is_a?(Array) && ((v1 = values.at(1)).is_a?(Array) || v1.is_a?(Dataset) || v1.is_a?(LiteralString))
      columns, values = v0, v1
      raise(Error, "Different number of values and columns given to insert_sql") if values.is_a?(Array) and columns.length != values.length
    end
  end

  columns = columns.map{|k| literal(String === k ? k.to_sym : k)}
  clone(:columns=>columns, :values=>values)._insert_sql
end

#inspectObject

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



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# File 'lib/sequel/lib/sequel/dataset.rb', line 210

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

#intersect(dataset, opts = {}) ⇒ Object

Adds an INTERSECT clause using a second dataset object. An INTERSECT compound dataset returns all rows in both the current dataset and the given dataset. Raises an InvalidOperation if the operation is not supported. Options:

  • :all - Set to true to use INTERSECT ALL instead of INTERSECT, so duplicate rows can occur

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

    DB.intersect(DB).sql #=> “SELECT * FROM items INTERSECT SELECT * FROM other_items”

Raises:



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 403

def intersect(dataset, opts={})
  opts = {:all=>opts} unless opts.is_a?(Hash)
  raise(InvalidOperation, "INTERSECT not supported") unless supports_intersect_except?
  raise(InvalidOperation, "INTERSECT ALL not supported") if opts[:all] && !supports_intersect_except_all?
  compound_clone(:intersect, dataset, opts)
end

#interval(column) ⇒ Object

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



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

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

#invertObject

Inverts the current filter

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

Raises:



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 414

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

#join_clause_sql(jc) ⇒ Object

SQL fragment specifying a JOIN clause without ON or USING.



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 424

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/lib/sequel/dataset/sql.rb', line 433

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 (e.g. :inner)

  • 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_qualifier - 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/lib/sequel/dataset/sql.rb', line 472

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 = dataset_alias(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_alias
    if Sequel.condition_specifier?(expr)
      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/lib/sequel/dataset/sql.rb', line 438

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/lib/sequel/dataset/convenience.rb', line 140

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.

dataset.limit(10) # SQL: SELECT * FROM items LIMIT 10
dataset.limit(10, 20) # SQL: SELECT * FROM items LIMIT 10 OFFSET 20

Raises:



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 523

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/lib/sequel/dataset/sql.rb', line 551

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 = 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. Raises an error if both an argument and block are given. Examples:

ds.map(:id) => [1, 2, 3, ...]
ds.map{|r| r[:id] * 2} => [2, 4, 6, ...]


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# File 'lib/sequel/lib/sequel/dataset/convenience.rb', line 151

def map(column=nil, &block)
  if column
    raise(Error, MAP_ERROR_MSG) if block
    super(){|r| r[column]}
  else
    super(&block)
  end
end

#max(column) ⇒ Object

Returns the maximum value for the given column.



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# File 'lib/sequel/lib/sequel/dataset/convenience.rb', line 161

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/lib/sequel/dataset/convenience.rb', line 166

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

#multi_insert(hashes, opts = {}) ⇒ Object

This is a front end for import that allows you to submit an array of hashes instead of arrays of columns and values:

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.

You can also use the :slice or :commit_every option that import accepts.



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# File 'lib/sequel/lib/sequel/dataset/convenience.rb', line 180

def multi_insert(hashes, opts={})
  return if hashes.empty?
  columns = hashes.first.keys
  import(columns, hashes.map{|h| columns.map{|c| h[c]}}, opts)
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/lib/sequel/dataset/sql.rb', line 595

def multi_insert_sql(columns, values)
  values.map{|r| insert_sql(columns, r)}
end

#nakedObject

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/lib/sequel/dataset.rb', line 216

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.

dataset.filter(:a).or(:b) # SQL: SELECT * FROM items WHERE a OR b

Raises:



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 603

def or(*cond, &block)
  clause = (@opts[:having] ? :having : :where)
  raise(InvalidOperation, "No existing filter found.") unless @opts[clause]
  cond = cond.first if cond.size == 1
  clone(clause => SQL::BooleanExpression.new(:OR, @opts[clause], filter_expr(cond, &block)))
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. If a block is given, it is treated as a virtual row block, similar to filter.

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{|o| o.sum(:name)}.sql #=> 'SELECT * FROM items ORDER BY sum(name)'
ds.order(nil).sql #=> 'SELECT * FROM items'


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 623

def order(*columns, &block)
  columns += Array(Sequel.virtual_row(&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.

ds.order(:a).order(:b).sql #=> 'SELECT * FROM items ORDER BY b'
ds.order(:a).order_more(:b).sql #=> 'SELECT * FROM items ORDER BY a, b'


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 634

def order_more(*columns, &block)
  columns = @opts[:order] + columns if @opts[:order]
  order(*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/lib/sequel/dataset/sql.rb', line 641

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/lib/sequel/extensions/pagination.rb', line 11

def paginate(page_no, page_size, record_count=nil)
  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/lib/sequel/dataset/sql.rb', line 646

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

#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/lib/sequel/dataset/prepared_statements.rb', line 189

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

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



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# File 'lib/sequel/lib/sequel/extensions/pretty_table.rb', line 8

def print(*cols)
  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/lib/sequel/dataset/sql.rb', line 655

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

#qualify(table = first_source) ⇒ Object

Qualify to the given table, or first source if not table is given.



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

def qualify(table=first_source)
  qualify_to(table)
end

#qualify_to(table) ⇒ Object

Return a copy of the dataset with unqualified identifiers in the SELECT, WHERE, GROUP, HAVING, and ORDER clauses qualified by the given table. If no columns are currently selected, select all columns of the given table.



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 668

def qualify_to(table)
  o = @opts
  return clone if o[:sql]
  h = {}
  (o.keys & QUALIFY_KEYS).each do |k|
    h[k] = qualified_expression(o[k], table)
  end
  h[:select] = [SQL::ColumnAll.new(table)] if !o[:select] || o[:select].empty?
  clone(h)
end

#qualify_to_first_sourceObject

Qualify the dataset to its current first source. This is useful if you have unqualified identifiers in the query that all refer to the first source, and you want to join to another table which has columns with the same name as columns in the current dataset. See qualify_to.



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 684

def qualify_to_first_source
  qualify_to(first_source)
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/lib/sequel/extensions/query.rb', line 30

def query(&block)
  copy = clone({})
  copy.extend(QueryBlockCopy)
  copy.instance_eval(&block)
  clone(copy.opts)
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/lib/sequel/dataset/sql.rb', line 691

def quote_identifier(name)
  return name if name.is_a?(LiteralString)
  name = name.value if name.is_a?(SQL::Identifier)
  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/lib/sequel/dataset.rb', line 223

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/lib/sequel/dataset/sql.rb', line 701

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/lib/sequel/dataset/sql.rb', line 709

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/lib/sequel/dataset/convenience.rb', line 188

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

#requires_sql_standard_datetimes?Boolean

Whether the dataset requires SQL standard datetimes (false by default, as most allow strings with ISO 8601 format.

Returns:

  • (Boolean)


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# File 'lib/sequel/lib/sequel/dataset.rb', line 229

def requires_sql_standard_datetimes?
  false
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/lib/sequel/dataset/sql.rb', line 715

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/lib/sequel/dataset/sql.rb', line 721

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. This also takes a virtual row block, similar to filter.

dataset.select(:a) # SELECT a FROM items
dataset.select(:a, :b) # SELECT a, b FROM items
dataset.select{|o| o.a, o.sum(:b)} # SELECT a, sum(b) FROM items


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 745

def select(*columns, &block)
  columns += Array(Sequel.virtual_row(&block)) if block
  m = []
  columns.map do |i|
    i.is_a?(Hash) ? m.concat(i.map{|k, v| SQL::AliasedExpression.new(k,v)}) : m << i
  end
  clone(:select => m)
end

#select_allObject

Returns a copy of the dataset selecting the wildcard.

dataset.select(:a).select_all # SELECT * FROM items


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 757

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.

dataset.select(:a).select(:b) # SELECT b FROM items
dataset.select(:a).select_more(:b) # SELECT a, b FROM items


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 766

def select_more(*columns, &block)
  columns = @opts[:select] + columns if @opts[:select]
  select(*columns, &block)
end

#select_sqlObject

Formats a SELECT statement

dataset.select_sql # => "SELECT * FROM items"


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 774

def select_sql
  return static_sql(@opts[:sql]) if @opts[:sql]
  clause_sql(:select)
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 (which is SELECT uses :read_only database and all other queries use the :default database).



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# File 'lib/sequel/lib/sequel/dataset.rb', line 236

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/lib/sequel/dataset.rb', line 242

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

#set_defaults(hash) ⇒ Object

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



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# File 'lib/sequel/lib/sequel/dataset.rb', line 248

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], :forty_two=>[:albums, :fourtwo, 42]).first
=> {:artists=>{:name=>artists.name}, :albums=>{:name=>albums.name, :fourtwo=>42}}

Arguments:

  • graph_aliases - Should be a hash with keys being symbols of column aliases, and values being arrays with two or three elements. The first element of the array should be the table alias symbol, and the second should be the actual column name symbol. If the array has a third element, it is used as the value returned, instead of table_alias.column_name.



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# File 'lib/sequel/lib/sequel/dataset/graph.rb', line 182

def set_graph_aliases(graph_aliases)
  ds = select(*graph_alias_columns(graph_aliases))
  ds.opts[:graph_aliases] = graph_aliases
  ds
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/lib/sequel/dataset.rb', line 254

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

#single_recordObject

Returns the first record in the dataset.



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# File 'lib/sequel/lib/sequel/dataset/convenience.rb', line 195

def single_record
  clone(:limit=>1).each{|r| return r}
  nil
end

#single_valueObject

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



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# File 'lib/sequel/lib/sequel/dataset/convenience.rb', line 202

def single_value
  if r = naked.clone(:graph=>false).single_record
    r.values.first
  end
end

#sqlObject

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



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 780

def sql
  select_sql
end

#subscript_sql(s) ⇒ Object

SQL fragment for specifying subscripts (SQL arrays)



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 785

def subscript_sql(s)
  "#{literal(s.f)}[#{expression_list(s.sub)}]"
end

#sum(column) ⇒ Object

Returns the sum for the given column.



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

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

#supports_cte?Boolean

Whether the dataset supports common table expressions (the WITH clause).

Returns:

  • (Boolean)


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

def supports_cte?
  select_clause_methods.include?(WITH_SUPPORTED)
end

#supports_distinct_on?Boolean

Whether the dataset supports the DISTINCT ON clause, true by default.

Returns:

  • (Boolean)


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# File 'lib/sequel/lib/sequel/dataset.rb', line 264

def supports_distinct_on?
  true
end

#supports_intersect_except?Boolean

Whether the dataset supports the INTERSECT and EXCEPT compound operations, true by default.

Returns:

  • (Boolean)


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# File 'lib/sequel/lib/sequel/dataset.rb', line 269

def supports_intersect_except?
  true
end

#supports_intersect_except_all?Boolean

Whether the dataset supports the INTERSECT ALL and EXCEPT ALL compound operations, true by default.

Returns:

  • (Boolean)


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# File 'lib/sequel/lib/sequel/dataset.rb', line 274

def supports_intersect_except_all?
  true
end

#supports_is_true?Boolean

Whether the dataset supports the IS TRUE syntax.

Returns:

  • (Boolean)


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# File 'lib/sequel/lib/sequel/dataset.rb', line 279

def supports_is_true?
  true
end

#supports_timestamp_timezones?Boolean

Whether the dataset supports timezones in literal timestamps

Returns:

  • (Boolean)


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# File 'lib/sequel/lib/sequel/dataset.rb', line 284

def supports_timestamp_timezones?
  false
end

#supports_timestamp_usecs?Boolean

Whether the dataset supports fractional seconds in literal timestamps

Returns:

  • (Boolean)


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# File 'lib/sequel/lib/sequel/dataset.rb', line 289

def supports_timestamp_usecs?
  true
end

#supports_window_functions?Boolean

Whether the dataset supports window functions.

Returns:

  • (Boolean)


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# File 'lib/sequel/lib/sequel/dataset.rb', line 294

def supports_window_functions?
  false
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 shouldn't use this.



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

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/lib/sequel/dataset/convenience.rb', line 234

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

#truncateObject

Truncates the dataset. Returns nil.



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# File 'lib/sequel/lib/sequel/dataset.rb', line 299

def truncate
  execute_ddl(truncate_sql)
end

#truncate_sqlObject

SQL query to truncate the table



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 790

def truncate_sql
  if opts[:sql]
    static_sql(opts[:sql])
  else
    check_modification_allowed!
    raise(InvalidOperation, "Can't truncate filtered datasets") if opts[:where]
    _truncate_sql(source_list(opts[:from]))
  end
end

#unfilteredObject

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

dataset.group(:a).having(:a=>1).where(:b).unfiltered # SELECT * FROM items GROUP BY a


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 803

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

#ungraphedObject

Remove the splitting of results into subhashes. Also removes metadata related to graphing, so you should not call graph any tables to this dataset after calling this method.



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

def ungraphed
  clone(:graph=>nil)
end

#ungroupedObject

Returns a copy of the dataset with no grouping (GROUP or HAVING clause) applied.

dataset.group(:a).having(:a=>1).where(:b).ungrouped # SELECT * FROM items WHERE b


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 810

def ungrouped
  clone(:group => nil, :having => nil)
end

#union(dataset, opts = {}) ⇒ Object

Adds a UNION clause using a second dataset object. A UNION compound dataset returns all rows in either the current dataset or the given dataset. Options:

  • :all - Set to true to use UNION ALL instead of UNION, so duplicate rows can occur

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

    DB.union(DB).sql #=> “SELECT * FROM items UNION SELECT * FROM other_items”



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 823

def union(dataset, opts={})
  opts = {:all=>opts} unless opts.is_a?(Hash)
  compound_clone(:union, dataset, opts)
end

#unlimitedObject

Returns a copy of the dataset with no limit or offset.

dataset.limit(10, 20).unlimited # SELECT * FROM items


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 831

def unlimited
  clone(:limit=>nil, :offset=>nil)
end

#unorderedObject

Returns a copy of the dataset with no order.

dataset.order(:a).unordered # SELECT * FROM items


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 838

def unordered
  order(nil)
end

#update(values = {}) ⇒ Object

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



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# File 'lib/sequel/lib/sequel/dataset.rb', line 305

def update(values={})
  execute_dui(update_sql(values))
end

#update_sql(values = {}) ⇒ Object

Formats an UPDATE statement using the given values.

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

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



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 849

def update_sql(values = {})
  return static_sql(opts[:sql]) if opts[:sql]
  check_modification_allowed!
  clone(:values=>values)._update_sql
end

#where(*cond, &block) ⇒ Object

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

dataset.group(:a).having(:a).filter(:b) # SELECT * FROM items GROUP BY a HAVING a AND b
dataset.group(:a).having(:a).where(:b) # SELECT * FROM items WHERE b GROUP BY a HAVING a


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 859

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

#window_function_sql(function, window) ⇒ Object

The SQL fragment for the given window function's function and window.



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 883

def window_function_sql(function, window)
  "#{literal(function)} OVER #{literal(window)}"
end

#window_sql(opts) ⇒ Object

The SQL fragment for the given window's options.

Raises:



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 864

def window_sql(opts)
  raise(Error, 'This dataset does not support window functions') unless supports_window_functions?
  window = literal(opts[:window]) if opts[:window]
  partition = "PARTITION BY #{expression_list(Array(opts[:partition]))}" if opts[:partition]
  order = "ORDER BY #{expression_list(Array(opts[:order]))}" if opts[:order]
  frame = case opts[:frame]
    when nil
      nil
    when :all
      "ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING"
    when :rows
      "ROWS UNBOUNDED PRECEDING"
    else
      raise Error, "invalid window frame clause, should be :all, :rows, or nil"
  end
  "(#{[window, partition, order, frame].compact.join(' ')})"
end

#with(name, dataset, opts = {}) ⇒ Object

Add a simple common table expression (CTE) with the given name and a dataset that defines the CTE. A common table expression acts as an inline view for the query. Options:

  • :args - Specify the arguments/columns for the CTE, should be an array of symbols.

  • :recursive - Specify that this is a recursive CTE

Raises:



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 892

def with(name, dataset, opts={})
  raise(Error, 'This datatset does not support common table expressions') unless supports_cte?
  clone(:with=>(@opts[:with]||[]) + [opts.merge(:name=>name, :dataset=>dataset)])
end

#with_recursive(name, nonrecursive, recursive, opts = {}) ⇒ Object

Add a recursive common table expression (CTE) with the given name, a dataset that defines the nonrecursive part of the CTE, and a dataset that defines the recursive part of the CTE. Options:

  • :args - Specify the arguments/columns for the CTE, should be an array of symbols.

  • :union_all - Set to false to use UNION instead of UNION ALL combining the nonrecursive and recursive parts.

Raises:



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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 902

def with_recursive(name, nonrecursive, recursive, opts={})
  raise(Error, 'This datatset does not support common table expressions') unless supports_cte?
  clone(:with=>(@opts[:with]||[]) + [opts.merge(:recursive=>true, :name=>name, :dataset=>nonrecursive.union(recursive, {:all=>opts[:union_all] != false, :from_self=>false}))])
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/graph, but change the SQL used to custom SQL.

dataset.with_sql('SELECT * FROM foo') # SELECT * FROM foo


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# File 'lib/sequel/lib/sequel/dataset/sql.rb', line 911

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