Class Sequel::Dataset
In: lib/sequel_core/adapters/jdbc.rb
lib/sequel_core/adapters/do.rb
lib/sequel_core/dataset.rb
lib/sequel_core/dataset/callback.rb
lib/sequel_core/dataset/convenience.rb
lib/sequel_core/dataset/pagination.rb
lib/sequel_core/dataset/prepared_statements.rb
lib/sequel_core/dataset/query.rb
lib/sequel_core/dataset/schema.rb
lib/sequel_core/dataset/sql.rb
lib/sequel_core/dataset/unsupported.rb
lib/sequel_core/dataset/stored_procedures.rb
lib/sequel_core/object_graph.rb
Parent: Sequel::Dataset

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.

Methods

<<   []   []=   add_graph_aliases   aliased_expression_sql   all   and   array_sql   as   avg   call   case_expression_sql   clone   column_all_sql   columns   columns!   complex_expression_sql   count   create_or_replace_view   create_view   dataset_classes   def_mutation_method   def_mutation_method   delete   delete_sql   distinct   each   each_page   empty?   except   exclude   exists   fetch_rows   fetch_rows   fetch_rows   filter   first   first_source   from   from_self   function_sql   get   graph   grep   group   group_and_count   group_by   having   import   inherited   insert   insert_multiple   insert_sql   inspect   intersect   interval   invert   irregular_function_sql   join_clause_sql   join_on_clause_sql   join_table   join_using_clause_sql   last   limit   literal   literal   literal   map   max   min   model_classes   multi_insert   multi_insert_sql   naked   new   options_overlap   or   order   order_by   order_more   ordered_expression_sql   paginate   placeholder_literal_string_sql   polymorphic_key   prepare   prepare   print   qualified_identifier_sql   query   quote_column_ref   quote_identifier   quote_identifiers?   quote_schema_table   quoted_identifier   range   reverse   reverse_order   schema_and_table   select   select_all   select_more   select_sql   server   set   set_defaults   set_graph_aliases   set_model   set_overrides   single_record   single_value   size   sql   subscript_sql   sum   symbol_to_column_ref   table_exists?   to_csv   to_hash   to_prepared_statement   to_table_reference   transform   transform_load   transform_save   unfiltered   union   uniq   unordered   upcase_identifiers=   upcase_identifiers?   update   update_sql   where  

Included Modules

StoredProcedures Enumerable

Classes and Modules

Module Sequel::Dataset::ArgumentMapper
Module Sequel::Dataset::Pagination
Module Sequel::Dataset::PreparedStatementMethods
Module Sequel::Dataset::QueryBlockCopy
Module Sequel::Dataset::StoredProcedureMethods
Module Sequel::Dataset::StoredProcedures
Module Sequel::Dataset::UnnumberedArgumentMapper
Module Sequel::Dataset::UnsupportedIntersectExcept
Module Sequel::Dataset::UnsupportedIntersectExceptAll

Constants

COLUMN_CHANGE_OPTS = [:select, :sql, :from, :join].freeze   The dataset options that require the removal of cached columns if changed.
DATASET_CLASSES = []   Array of all subclasses of Dataset
MUTATION_METHODS = %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_model set_overrides sort sort_by unfiltered union unordered where'.collect{|x| x.to_sym}   All methods that should have a ! method added that modifies the receiver.
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')}
COMMA_SEPARATOR = ', '.freeze
COUNT_OF_ALL_AS_COUNT = SQL::Function.new(:count, '*'.lit).as(:count)
PREPARED_ARG_PLACEHOLDER = '?'.lit.freeze
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]
DATE_FORMAT = "DATE '%Y-%m-%d'".freeze
N_ARITY_OPERATORS = ::Sequel::SQL::ComplexExpression::N_ARITY_OPERATORS
NULL = "NULL".freeze
QUESTION_MARK = '?'.freeze
STOCK_COUNT_OPTS = {:select => ["COUNT(*)".lit], :order => nil}.freeze
SELECT_CLAUSE_ORDER = %w'distinct columns from join where group having compounds order limit'.freeze
TIMESTAMP_FORMAT = "TIMESTAMP '%Y-%m-%d %H:%M:%S'".freeze
TWO_ARITY_OPERATORS = ::Sequel::SQL::ComplexExpression::TWO_ARITY_OPERATORS
WILDCARD = '*'.freeze

External Aliases

inner_join -> join

Attributes

db  [RW]  The database that corresponds to this dataset
identifier_input_method  [RW]  Set the method to call on identifiers going into the database for this dataset
identifier_output_method  [RW]  Set the method to call on identifiers coming the database for this dataset
opts  [RW]  The hash of options for this dataset, keys are symbols.
quote_identifiers  [W]  Whether to quote identifiers for this dataset
row_proc  [RW]  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.

Public Class methods

The array of dataset subclasses.

[Source]

     # File lib/sequel_core/dataset.rb, line 116
116:     def self.dataset_classes
117:       DATASET_CLASSES
118:     end

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.

[Source]

     # File lib/sequel_core/dataset.rb, line 123
123:     def self.def_mutation_method(*meths)
124:       meths.each do |meth|
125:         class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end")
126:       end
127:     end

Add the subclass to the array of subclasses.

[Source]

     # File lib/sequel_core/dataset.rb, line 130
130:     def self.inherited(c)
131:       DATASET_CLASSES << c
132:     end

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.

[Source]

     # File lib/sequel_core/dataset.rb, line 103
103:     def initialize(db, opts = nil)
104:       @db = db
105:       @quote_identifiers = db.quote_identifiers? if db.respond_to?(:quote_identifiers?)
106:       @identifier_input_method = db.identifier_input_method if db.respond_to?(:identifier_input_method)
107:       @identifier_output_method = db.identifier_output_method if db.respond_to?(:identifier_output_method)
108:       @opts = opts || {}
109:       @row_proc = nil
110:       @transform = nil
111:     end

Public Instance methods

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

[Source]

     # File lib/sequel_core/dataset.rb, line 138
138:     def <<(*args)
139:       insert(*args)
140:     end

Returns the first record matching the conditions.

[Source]

   # File lib/sequel_core/dataset/convenience.rb, line 7
7:     def [](*conditions)
8:       first(*conditions)
9:     end

Update all records matching the conditions with the values specified.

[Source]

    # File lib/sequel_core/dataset/convenience.rb, line 13
13:     def []=(conditions, values)
14:       filter(conditions).update(values)
15:     end

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.

[Source]

     # File lib/sequel_core/object_graph.rb, line 167
167:     def add_graph_aliases(graph_aliases)
168:       ds = select_more(*graph_alias_columns(graph_aliases))
169:       ds.opts[:graph_aliases] = (ds.opts[:graph_aliases] || {}).merge(graph_aliases)
170:       ds
171:     end

SQL fragment for the aliased expression

[Source]

    # File lib/sequel_core/dataset/sql.rb, line 29
29:     def aliased_expression_sql(ae)
30:       as_sql(literal(ae.expression), ae.aliaz)
31:     end

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.

[Source]

     # File lib/sequel_core/dataset.rb, line 150
150:     def all(opts = nil, &block)
151:       a = []
152:       each(opts) {|r| a << r}
153:       post_load(a)
154:       a.each(&block) if block
155:       a
156:     end

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.

[Source]

    # File lib/sequel_core/dataset/sql.rb, line 23
23:     def and(*cond, &block)
24:       raise(Error::NoExistingFilter, "No existing filter found.") unless @opts[:having] || @opts[:where]
25:       filter(*cond, &block)
26:     end

SQL fragment for the SQL array.

[Source]

    # File lib/sequel_core/dataset/sql.rb, line 34
34:     def array_sql(a)
35:       a.empty? ? '(NULL)' : "(#{expression_list(a)})"     
36:     end

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.

[Source]

     # File lib/sequel_core/dataset.rb, line 144
144:     def as(aliaz)
145:       ::Sequel::SQL::AliasedExpression.new(self, aliaz)
146:     end

Returns the average value for the given column.

[Source]

    # File lib/sequel_core/dataset/convenience.rb, line 18
18:     def avg(column)
19:       get(SQL::Function.new(:avg, column))
20:     end

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.

[Source]

     # File lib/sequel_core/dataset/prepared_statements.rb, line 181
181:     def call(type, bind_variables={}, values=nil)
182:       prepare(type, nil, values).call(bind_variables)
183:     end

SQL fragment for specifying given CaseExpression.

[Source]

    # File lib/sequel_core/dataset/sql.rb, line 39
39:     def case_expression_sql(ce)
40:       sql = '(CASE '
41:       sql << "#{literal(ce.expression)} " if ce.expression
42:       ce.conditions.collect{ |c,r|
43:         sql << "WHEN #{literal(c)} THEN #{literal(r)} "
44:       }
45:       sql << "ELSE #{literal(ce.default)} END)"
46:     end

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.

[Source]

     # File lib/sequel_core/dataset.rb, line 161
161:     def clone(opts = {})
162:       c = super()
163:       c.opts = @opts.merge(opts)
164:       c.instance_variable_set(:@columns, nil) if opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
165:       c
166:     end

SQL fragment for specifying all columns in a given table.

[Source]

    # File lib/sequel_core/dataset/sql.rb, line 49
49:     def column_all_sql(ca)
50:       "#{quote_schema_table(ca.table)}.*"
51:     end

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 Schema::SQL#schema.

[Source]

     # File lib/sequel_core/dataset.rb, line 174
174:     def columns
175:       return @columns if @columns
176:       ds = unfiltered.unordered.clone(:distinct => nil)
177:       ds.single_record
178:       @columns = ds.instance_variable_get(:@columns)
179:       @columns || []
180:     end

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

[Source]

     # File lib/sequel_core/dataset.rb, line 184
184:     def columns!
185:       @columns = nil
186:       columns
187:     end

SQL fragment for complex expressions

[Source]

    # File lib/sequel_core/dataset/sql.rb, line 54
54:     def complex_expression_sql(op, args)
55:       case op
56:       when *TWO_ARITY_OPERATORS
57:         "(#{literal(args.at(0))} #{op} #{literal(args.at(1))})"
58:       when *N_ARITY_OPERATORS
59:         "(#{args.collect{|a| literal(a)}.join(" #{op} ")})"
60:       when :NOT
61:         "NOT #{literal(args.at(0))}"
62:       when :NOOP
63:         literal(args.at(0))
64:       when 'B~''B~'
65:         "~#{literal(args.at(0))}"
66:       else
67:         raise(Sequel::Error, "invalid operator #{op}")
68:       end
69:     end

Returns the number of records in the dataset.

[Source]

    # File lib/sequel_core/dataset/sql.rb, line 72
72:     def count
73:       options_overlap(COUNT_FROM_SELF_OPTS) ? from_self.count : single_value(STOCK_COUNT_OPTS).to_i
74:     end

Creates or replaces a view in the database with the given named based on the current dataset.

[Source]

    # File lib/sequel_core/dataset/schema.rb, line 11
11:     def create_or_replace_view(name)
12:       @db.create_or_replace_view(name, self)
13:     end

Creates a view in the database with the given named based on the current dataset.

[Source]

   # File lib/sequel_core/dataset/schema.rb, line 5
5:     def create_view(name)
6:       @db.create_view(name, self)
7:     end

Add a mutation method to this dataset instance.

[Source]

     # File lib/sequel_core/dataset.rb, line 190
190:     def def_mutation_method(*meths)
191:       meths.each do |meth|
192:         instance_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end")
193:       end
194:     end

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

[Source]

     # File lib/sequel_core/dataset.rb, line 198
198:     def delete(*args)
199:       execute_dui(delete_sql(*args))
200:     end

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)"

[Source]

    # File lib/sequel_core/dataset/sql.rb, line 81
81:     def delete_sql(opts = nil)
82:       opts = opts ? @opts.merge(opts) : @opts
83: 
84:       return static_sql(opts[:sql]) if opts[:sql]
85: 
86:       if opts[:group]
87:         raise Error::InvalidOperation, "Grouped datasets cannot be deleted from"
88:       elsif opts[:from].is_a?(Array) && opts[:from].size > 1
89:         raise Error::InvalidOperation, "Joined datasets cannot be deleted from"
90:       end
91: 
92:       sql = "DELETE FROM #{source_list(opts[:from])}"
93: 
94:       if where = opts[:where]
95:         sql << " WHERE #{literal(where)}"
96:       end
97: 
98:       sql
99:     end
distinct(*args)

Alias for uniq

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

[Source]

     # File lib/sequel_core/dataset.rb, line 204
204:     def each(opts = nil, &block)
205:       if opts && opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
206:         prev_columns = @columns
207:         begin
208:           _each(opts, &block)
209:         ensure
210:           @columns = prev_columns
211:         end
212:       else
213:         _each(opts, &block)
214:       end
215:       self
216:     end

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

[Source]

    # File lib/sequel_core/dataset/pagination.rb, line 16
16:     def each_page(page_size, &block)
17:       raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
18:       record_count = count
19:       total_pages = (record_count / page_size.to_f).ceil
20:       (1..total_pages).each{|page_no| yield paginate(page_no, page_size, record_count)}
21:       self
22:     end

Returns true if no records exists in the dataset

[Source]

    # File lib/sequel_core/dataset/convenience.rb, line 23
23:     def empty?
24:       get(1).nil?
25:     end

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"

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 106
106:     def except(dataset, all = false)
107:       compound_clone(:except, dataset, all)
108:     end

Performs the inverse of Dataset#filter.

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 114
114:     def exclude(*cond, &block)
115:       clause = (@opts[:having] ? :having : :where)
116:       cond = cond.first if cond.size == 1
117:       cond = cond.sql_or if (Hash === cond) || ((Array === cond) && (cond.all_two_pairs?))
118:       cond = filter_expr(cond, &block)
119:       cond = SQL::BooleanExpression.invert(cond)
120:       cond = SQL::BooleanExpression.new(:AND, @opts[clause], cond) if @opts[clause]
121:       clone(clause => cond)
122:     end

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)"

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 128
128:     def exists(opts = nil)
129:       "EXISTS (#{select_sql(opts)})".lit
130:     end

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.

[Source]

     # File lib/sequel_core/dataset.rb, line 221
221:     def fetch_rows(sql, &block)
222:       raise NotImplementedError, NOTIMPL_MSG
223:     end

Execute the SQL on the database and yield the rows as hashes with symbol keys.

[Source]

     # File lib/sequel_core/adapters/do.rb, line 192
192:       def fetch_rows(sql)
193:         execute(sql) do |reader|
194:           cols = @columns = reader.fields.map{|f| output_identifier(f)}
195:           while(reader.next!) do
196:             h = {}
197:             cols.zip(reader.values).each{|k, v| h[k] = v}
198:             yield h
199:           end
200:         end
201:         self
202:       end

Correctly return rows from the database and return them as hashes.

[Source]

     # File lib/sequel_core/adapters/jdbc.rb, line 412
412:       def fetch_rows(sql, &block)
413:         execute(sql){|result| process_result_set(result, &block)}
414:         self
415:       end

Returns a copy of the dataset with the given conditions imposed upon it. If the query has been grouped, then the conditions are imposed in the HAVING clause. If not, then they are imposed in the WHERE clause. Filter

filter accepts the following argument types:

  • Hash - list of equality 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 blockless 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.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 176
176:     def filter(*cond, &block)
177:       clause = (@opts[:having] ? :having : :where)
178:       cond = cond.first if cond.size == 1
179:       cond = transform_save(cond) if @transform if cond.is_a?(Hash)
180:       cond = filter_expr(cond, &block)
181:       cond = SQL::BooleanExpression.new(:AND, @opts[clause], cond) if @opts[clause] && !@opts[clause].blank?
182:       clone(clause => cond)
183:     end

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}]

[Source]

    # File lib/sequel_core/dataset/convenience.rb, line 48
48:     def first(*args, &block)
49:       ds = block ? filter(&block) : self
50: 
51:       if args.empty?
52:         ds.single_record
53:       else
54:         args = (args.size == 1) ? args.first : args
55:         if Integer === args
56:           ds.limit(args).all
57:         else
58:           ds.filter(args).single_record
59:         end
60:       end
61:     end

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 actual table name, not the alias.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 189
189:     def first_source
190:       source = @opts[:from]
191:       if source.nil? || source.empty?
192:         raise Error, 'No source specified for query'
193:       end
194:       case s = source.first
195:       when Hash
196:         s.values.first
197:       when Symbol
198:         sch, table, aliaz = split_symbol(s)
199:         aliaz ? aliaz.to_sym : s
200:       else
201:         s
202:       end
203:     end

Returns a copy of the dataset with the source changed.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 206
206:     def from(*source)
207:       clone(:from => source)
208:     end

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)"

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 215
215:     def from_self
216:       fs = {}
217:       @opts.keys.each{|k| fs[k] = nil} 
218:       fs[:from] = [self]
219:       clone(fs)
220:     end

SQL fragment specifying an SQL function call

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 223
223:     def function_sql(f)
224:       args = f.args
225:       "#{f.f}#{args.empty? ? '()' : literal(args)}"
226:     end

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

[Source]

    # File lib/sequel_core/dataset/convenience.rb, line 64
64:     def get(column)
65:       select(column).single_value
66:     end

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.

[Source]

     # File lib/sequel_core/object_graph.rb, line 48
 48:     def graph(dataset, join_conditions = nil, options = {}, &block)
 49:       # Allow the use of a model, dataset, or symbol as the first argument
 50:       # Find the table name/dataset based on the argument
 51:       dataset = dataset.dataset if dataset.respond_to?(:dataset)
 52:       case dataset
 53:       when Symbol
 54:         table = dataset
 55:         dataset = @db[dataset]
 56:       when ::Sequel::Dataset
 57:         table = dataset.first_source
 58:       else
 59:         raise Error, "The dataset argument should be a symbol, dataset, or model"
 60:       end
 61: 
 62:       # Raise Sequel::Error with explanation that the table alias has been used
 63:       raise_alias_error = lambda do
 64:         raise(Error, "this #{options[:table_alias] ? 'alias' : 'table'} has already been been used, please specify " \
 65:           "#{options[:table_alias] ? 'a different alias' : 'an alias via the :table_alias option'}") 
 66:       end
 67: 
 68:       # Only allow table aliases that haven't been used
 69:       table_alias = options[:table_alias] || table
 70:       raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)
 71: 
 72:       # Join the table early in order to avoid cloning the dataset twice
 73:       ds = join_table(options[:join_type] || :left_outer, table, join_conditions, :table_alias=>table_alias, :implicit_qualifier=>options[:implicit_qualifier], &block)
 74:       opts = ds.opts
 75: 
 76:       # Whether to include the table in the result set
 77:       add_table = options[:select] == false ? false : true
 78:       # Whether to add the columns to the list of column aliases
 79:       add_columns = !ds.opts.include?(:graph_aliases)
 80: 
 81:       # Setup the initial graph data structure if it doesn't exist
 82:       unless graph = opts[:graph]
 83:         master = ds.first_source
 84:         raise_alias_error.call if master == table_alias
 85:         # Master hash storing all .graph related information
 86:         graph = opts[:graph] = {}
 87:         # Associates column aliases back to tables and columns
 88:         column_aliases = graph[:column_aliases] = {}
 89:         # Associates table alias (the master is never aliased)
 90:         table_aliases = graph[:table_aliases] = {master=>self}
 91:         # Keep track of the alias numbers used
 92:         ca_num = graph[:column_alias_num] = Hash.new(0)
 93:         # All columns in the master table are never
 94:         # aliased, but are not included if set_graph_aliases
 95:         # has been used.
 96:         if add_columns
 97:           select = opts[:select] = []
 98:           columns.each do |column|
 99:             column_aliases[column] = [master, column]
100:             select.push(column.qualify(master))
101:           end
102:         end
103:       end
104: 
105:       # Add the table alias to the list of aliases
106:       # Even if it isn't been used in the result set,
107:       # we add a key for it with a nil value so we can check if it
108:       # is used more than once
109:       table_aliases = graph[:table_aliases]
110:       table_aliases[table_alias] = add_table ? dataset : nil
111: 
112:       # Add the columns to the selection unless we are ignoring them
113:       if add_table && add_columns
114:         select = opts[:select]
115:         column_aliases = graph[:column_aliases]
116:         ca_num = graph[:column_alias_num]
117:         # Which columns to add to the result set
118:         cols = options[:select] || dataset.columns
119:         # If the column hasn't been used yet, don't alias it.
120:         # If it has been used, try table_column.
121:         # If that has been used, try table_column_N 
122:         # using the next value of N that we know hasn't been
123:         # used
124:         cols.each do |column|
125:           col_alias, identifier = if column_aliases[column]
126:             column_alias = "#{table_alias}_#{column}""#{table_alias}_#{column}"
127:             if column_aliases[column_alias]
128:               column_alias_num = ca_num[column_alias]
129:               column_alias = "#{column_alias}_#{column_alias_num}""#{column_alias}_#{column_alias_num}" 
130:               ca_num[column_alias] += 1
131:             end
132:             [column_alias, column.qualify(table_alias).as(column_alias)]
133:           else
134:             [column, column.qualify(table_alias)]
135:           end
136:           column_aliases[col_alias] = [table_alias, column]
137:           select.push(identifier)
138:         end
139:       end
140:       ds
141:     end

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.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 233
233:     def grep(cols, terms)
234:       filter(SQL::BooleanExpression.new(:OR, *Array(cols).collect{|c| SQL::StringExpression.like(c, *terms)}))
235:     end

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 239
239:     def group(*columns)
240:       clone(:group => columns)
241:     end

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

[Source]

    # File lib/sequel_core/dataset/convenience.rb, line 69
69:     def group_and_count(*columns)
70:       group(*columns).select(*(columns + [COUNT_OF_ALL_AS_COUNT])).order(:count)
71:     end
group_by(*columns)

Alias for group

Returns a copy of the dataset with the having conditions changed. Raises an error if the dataset has not been grouped. See also filter.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 246
246:     def having(*cond, &block)
247:       raise(Error::InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group]
248:       clone(:having=>{}).filter(*cond, &block)
249:     end
import(*args)

Alias for multi_insert

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.

[Source]

     # File lib/sequel_core/dataset.rb, line 227
227:     def insert(*values)
228:       execute_insert(insert_sql(*values))
229:     end

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.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 255
255:     def insert_multiple(array, &block)
256:       if block
257:         array.each {|i| insert(block[i])}
258:       else
259:         array.each {|i| insert(i)}
260:       end
261:     end

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)'

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 271
271:     def insert_sql(*values)
272:       return static_sql(@opts[:sql]) if @opts[:sql]
273: 
274:       from = source_list(@opts[:from])
275:       case values.size
276:       when 0
277:         values = {}
278:       when 1
279:         vals = values.at(0)
280:         if vals.is_one_of?(Hash, Dataset, Array)
281:           values = vals
282:         elsif vals.respond_to?(:values)
283:           values = vals.values
284:         end
285:       end
286: 
287:       case values
288:       when Array
289:         if values.empty?
290:           insert_default_values_sql
291:         else
292:           "INSERT INTO #{from} VALUES #{literal(values)}"
293:         end
294:       when Hash
295:         values = @opts[:defaults].merge(values) if @opts[:defaults]
296:         values = values.merge(@opts[:overrides]) if @opts[:overrides]
297:         values = transform_save(values) if @transform
298:         if values.empty?
299:           insert_default_values_sql
300:         else
301:           fl, vl = [], []
302:           values.each do |k, v|
303:             fl << literal(String === k ? k.to_sym : k)
304:             vl << literal(v)
305:           end
306:           "INSERT INTO #{from} (#{fl.join(COMMA_SEPARATOR)}) VALUES (#{vl.join(COMMA_SEPARATOR)})"
307:         end
308:       when Dataset
309:         "INSERT INTO #{from} #{literal(values)}"
310:       end
311:     end

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

[Source]

     # File lib/sequel_core/dataset.rb, line 233
233:     def inspect
234:       "#<#{self.class}: #{sql.inspect}>"
235:     end

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"

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 318
318:     def intersect(dataset, all = false)
319:       compound_clone(:intersect, dataset, all)
320:     end

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

[Source]

    # File lib/sequel_core/dataset/convenience.rb, line 75
75:     def interval(column)
76:       get("(max(#{literal(column)}) - min(#{literal(column)}))".lit)
77:     end

Inverts the current filter

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 326
326:     def invert
327:       having, where = @opts[:having], @opts[:where]
328:       raise(Error, "No current filter") unless having || where
329:       o = {}
330:       o[:having] = SQL::BooleanExpression.invert(having) if having
331:       o[:where] = SQL::BooleanExpression.invert(where) if where
332:       clone(o)
333:     end

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 336
336:     def irregular_function_sql(f)
337:       "#{f.f}(#{literal(f.arg1)} #{f.joiner} #{literal(f.arg2)})"
338:     end

SQL fragment specifying a JOIN clause without ON or USING.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 341
341:     def join_clause_sql(jc)
342:       table = jc.table
343:       table_alias = jc.table_alias
344:       table_alias = nil if table == table_alias
345:       tref = table_ref(table)
346:       " #{join_type_sql(jc.join_type)} #{table_alias ? as_sql(tref, table_alias) : tref}"
347:     end

SQL fragment specifying a JOIN clause with ON.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 350
350:     def join_on_clause_sql(jc)
351:       "#{join_clause_sql(jc)} ON #{literal(filter_expr(jc.on))}"
352:     end

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.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 389
389:     def join_table(type, table, expr=nil, options={}, &block)
390:       if options.is_one_of?(Symbol, String)
391:         table_alias = options
392:         last_alias = nil 
393:       else
394:         table_alias = options[:table_alias]
395:         last_alias = options[:implicit_qualifier]
396:       end
397:       if Dataset === table
398:         if table_alias.nil?
399:           table_alias_num = (@opts[:num_dataset_sources] || 0) + 1
400:           table_alias = "t#{table_alias_num}"
401:         end
402:         table_name = table_alias
403:       else
404:         table = table.table_name if table.respond_to?(:table_name)
405:         table_name = table_alias || table
406:       end
407: 
408:       join = if expr.nil? and !block_given?
409:         SQL::JoinClause.new(type, table, table_alias)
410:       elsif Array === expr and !expr.empty? and expr.all?{|x| Symbol === x}
411:         raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block_given?
412:         SQL::JoinUsingClause.new(expr, type, table, table_alias)
413:       else
414:         last_alias ||= @opts[:last_joined_table] || (first_source.is_a?(Dataset) ? 't1' : first_source)
415:         if Hash === expr or (Array === expr and expr.all_two_pairs?)
416:           expr = expr.collect do |k, v|
417:             k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
418:             v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
419:             [k,v]
420:           end
421:         end
422:         if block_given?
423:           expr2 = yield(table_name, last_alias, @opts[:join] || [])
424:           expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
425:         end
426:         SQL::JoinOnClause.new(expr, type, table, table_alias)
427:       end
428: 
429:       opts = {:join => (@opts[:join] || []) + [join], :last_joined_table => table_name}
430:       opts[:num_dataset_sources] = table_alias_num if table_alias_num
431:       clone(opts)
432:     end

SQL fragment specifying a JOIN clause with USING.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 355
355:     def join_using_clause_sql(jc)
356:       "#{join_clause_sql(jc)} USING (#{column_list(jc.using)})"
357:     end

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.

[Source]

    # File lib/sequel_core/dataset/convenience.rb, line 83
83:     def last(*args, &block)
84:       raise(Error, 'No order specified') unless @opts[:order]
85:       reverse.first(*args, &block)
86:     end

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.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 437
437:     def limit(l, o = nil)
438:       return from_self.limit(l, o) if @opts[:sql]
439: 
440:       if Range === l
441:         o = l.first
442:         l = l.interval + 1
443:       end
444:       l = l.to_i
445:       raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
446:       opts = {:limit => l}
447:       if o
448:         o = o.to_i
449:         raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
450:         opts[:offset] = o
451:       end
452:       clone(opts)
453:     end

Use the ISO values for dates and times.

[Source]

     # File lib/sequel_core/adapters/jdbc.rb, line 418
418:       def literal(v)
419:         case v
420:         when Time
421:           literal(v.iso8601)
422:         when Date, DateTime, Java::JavaSql::Timestamp, Java::JavaSql::Date
423:           literal(v.to_s)
424:         else
425:           super
426:         end
427:       end

Handle the usual time class overrides.

[Source]

     # File lib/sequel_core/adapters/do.rb, line 179
179:       def literal(v)
180:         case v
181:         when Time
182:           literal(v.iso8601)
183:         when Date, DateTime
184:           literal(v.to_s)
185:         else
186:           super
187:         end
188:       end

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.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 465
465:     def literal(v)
466:       case v
467:       when LiteralString
468:         v
469:       when String
470:         "'#{v.gsub(/\\/, "\\\\\\\\").gsub(/'/, "''")}'"
471:       when Integer, Float
472:         v.to_s
473:       when BigDecimal
474:         d = v.to_s("F")
475:         d = "'#{d}'" if v.nan? || v.infinite?
476:         d
477:       when NilClass
478:         NULL
479:       when TrueClass
480:         BOOL_TRUE
481:       when FalseClass
482:         BOOL_FALSE
483:       when Symbol
484:         symbol_to_column_ref(v)
485:       when ::Sequel::SQL::Expression
486:         v.to_s(self)
487:       when Array
488:         v.all_two_pairs? ? literal(v.sql_expr) : array_sql(v)
489:       when Hash
490:         literal(v.sql_expr)
491:       when Time, DateTime
492:         v.strftime(TIMESTAMP_FORMAT)
493:       when Date
494:         v.strftime(DATE_FORMAT)
495:       when Dataset
496:         "(#{subselect_sql(v)})"
497:       else
498:         raise Error, "can't express #{v.inspect} as a SQL literal"
499:       end
500:     end

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

[Source]

    # File lib/sequel_core/dataset/convenience.rb, line 90
90:     def map(column_name = nil, &block)
91:       if column_name
92:         super() {|r| r[column_name]}
93:       else
94:         super(&block)
95:       end
96:     end

Returns the maximum value for the given column.

[Source]

     # File lib/sequel_core/dataset/convenience.rb, line 99
 99:     def max(column)
100:       get(SQL::Function.new(:max, column))
101:     end

Returns the minimum value for the given column.

[Source]

     # File lib/sequel_core/dataset/convenience.rb, line 104
104:     def min(column)
105:       get(SQL::Function.new(:min, column))
106:     end

Returns the the model classes associated with the dataset as a hash. If the dataset is associated with a single model class, a key of nil is used. For datasets with polymorphic models, the keys are values of the polymorphic column and the values are the corresponding model classes to which they map.

[Source]

     # File lib/sequel_core/dataset.rb, line 242
242:     def model_classes
243:       @opts[:models]
244:     end

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)

[Source]

     # File lib/sequel_core/dataset/convenience.rb, line 130
130:     def multi_insert(*args)
131:       if args.empty?
132:         return
133:       elsif args[0].is_a?(Array) && args[1].is_a?(Array)
134:         columns, values, opts = *args
135:       elsif args[0].is_a?(Array) && args[1].is_a?(Dataset)
136:         table = @opts[:from].first
137:         columns, dataset = *args
138:         sql = "INSERT INTO #{quote_identifier(table)} (#{identifier_list(columns)}) VALUES #{literal(dataset)}"
139:         return @db.transaction{execute_dui(sql)}
140:       else
141:         # we assume that an array of hashes is given
142:         hashes, opts = *args
143:         return if hashes.empty?
144:         columns = hashes.first.keys
145:         # convert the hashes into arrays
146:         values = hashes.map {|h| columns.map {|c| h[c]}}
147:       end
148:       # make sure there's work to do
149:       return if columns.empty? || values.empty?
150:       
151:       slice_size = opts && (opts[:commit_every] || opts[:slice])
152:       
153:       if slice_size
154:         values.each_slice(slice_size) do |slice|
155:           statements = multi_insert_sql(columns, slice)
156:           @db.transaction{statements.each{|st| execute_dui(st)}}
157:         end
158:       else
159:         statements = multi_insert_sql(columns, values)
160:         @db.transaction{statements.each{|st| execute_dui(st)}}
161:       end
162:     end

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.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 508
508:     def multi_insert_sql(columns, values)
509:       table = quote_identifier(@opts[:from].first)
510:       columns = identifier_list(columns)
511:       values.map do |r|
512:         "INSERT INTO #{table} (#{columns}) VALUES #{literal(r)}"
513:       end
514:     end

Returns a naked dataset clone - i.e. a dataset that returns records as hashes rather than model objects.

[Source]

     # File lib/sequel_core/dataset.rb, line 248
248:     def naked
249:       clone.set_model(nil)
250:     end

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 518
518:     def or(*cond, &block)
519:       clause = (@opts[:having] ? :having : :where)
520:       cond = cond.first if cond.size == 1
521:       if @opts[clause]
522:         clone(clause => SQL::BooleanExpression.new(:OR, @opts[clause], filter_expr(cond, &block)))
523:       else
524:         raise Error::NoExistingFilter, "No existing filter found."
525:       end
526:     end

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'

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 540
540:     def order(*order)
541:       clone(:order => (order.compact.empty?) ? nil : order)
542:     end
order_by(*order)

Alias for order

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 547
547:     def order_more(*order)
548:       order(*((@opts[:order] || []) + order))
549:     end

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 553
553:     def ordered_expression_sql(oe)
554:       "#{literal(oe.expression)} #{oe.descending ? 'DESC' : 'ASC'}"
555:     end

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.

[Source]

    # File lib/sequel_core/dataset/pagination.rb, line 7
 7:     def paginate(page_no, page_size, record_count=nil)
 8:       raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
 9:       paginated = limit(page_size, (page_no - 1) * page_size)
10:       paginated.extend(Pagination)
11:       paginated.set_pagination_info(page_no, page_size, record_count || count)
12:     end

SQL fragment for a literal string with placeholders

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 558
558:     def placeholder_literal_string_sql(pls)
559:       args = pls.args.dup
560:       s = pls.str.gsub(QUESTION_MARK){literal(args.shift)}
561:       s = "(#{s})" if pls.parens
562:       s
563:     end

Returns the column name for the polymorphic key.

[Source]

     # File lib/sequel_core/dataset.rb, line 253
253:     def polymorphic_key
254:       @opts[:polymorphic_key]
255:     end

Create a named prepared statement that is stored in the database (and connection) for reuse.

[Source]

     # File lib/sequel_core/adapters/jdbc.rb, line 431
431:       def prepare(type, name=nil, values=nil)
432:         ps = to_prepared_statement(type, values)
433:         ps.extend(PreparedStatementMethods)
434:         if name
435:           ps.prepared_statement_name = name
436:           db.prepared_statements[name] = ps
437:         end
438:         ps
439:       end

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')

[Source]

     # File lib/sequel_core/dataset/prepared_statements.rb, line 194
194:     def prepare(type, name=nil, values=nil)
195:       ps = to_prepared_statement(type, values)
196:       db.prepared_statements[name] = ps if name
197:       ps
198:     end

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

[Source]

     # File lib/sequel_core/dataset/convenience.rb, line 166
166:     def print(*cols)
167:       Sequel::PrettyTable.print(naked.all, cols.empty? ? columns : cols)
168:     end

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 567
567:     def qualified_identifier_sql(qcr)
568:       [qcr.table, qcr.column].map{|x| x.is_one_of?(SQL::QualifiedIdentifier, SQL::Identifier, Symbol) ? literal(x) : quote_identifier(x)}.join('.')
569:     end

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.

[Source]

    # File lib/sequel_core/dataset/query.rb, line 19
19:     def query(&block)
20:       copy = clone({})
21:       copy.extend(QueryBlockCopy)
22:       copy.instance_eval(&block)
23:       clone(copy.opts)
24:     end
quote_column_ref(name)

Alias for quote_identifier

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.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 574
574:     def quote_identifier(name)
575:       return name if name.is_a?(LiteralString)
576:       name = input_identifier(name)
577:       name = quoted_identifier(name) if quote_identifiers?
578:       name
579:     end

Whether this dataset quotes identifiers.

[Source]

     # File lib/sequel_core/dataset.rb, line 258
258:     def quote_identifiers?
259:       @quote_identifiers
260:     end

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 584
584:     def quote_schema_table(table)
585:       schema, table = schema_and_table(table)
586:       "#{"#{quote_identifier(schema)}." if schema}#{quote_identifier(table)}"
587:     end

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).

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 592
592:     def quoted_identifier(name)
593:       "\"#{name.to_s.gsub('"', '""')}\""
594:     end

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

[Source]

     # File lib/sequel_core/dataset/convenience.rb, line 172
172:     def range(column)
173:       if r = select(SQL::Function.new(:min, column).as(:v1), SQL::Function.new(:max, column).as(:v2)).first
174:         (r[:v1]..r[:v2])
175:       end
176:     end
reverse(*order)

Alias for reverse_order

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 598
598:     def reverse_order(*order)
599:       order(*invert_order(order.empty? ? @opts[:order] : order))
600:     end

Split the schema information from the table

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 604
604:     def schema_and_table(table_name)
605:       sch = db.default_schema if db
606:       case table_name
607:       when Symbol
608:         s, t, a = split_symbol(table_name)
609:         [s||sch, t]
610:       when SQL::QualifiedIdentifier
611:         [table_name.table, table_name.column]
612:       when SQL::Identifier
613:         [sch, table_name.value]
614:       when String
615:         [sch, table_name]
616:       else
617:         raise Error, 'table_name should be a Symbol, SQL::QualifiedIdentifier, SQL::Identifier, or String'
618:       end
619:     end

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 623
623:     def select(*columns)
624:       clone(:select => columns)
625:     end

Returns a copy of the dataset selecting the wildcard.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 628
628:     def select_all
629:       clone(:select => nil)
630:     end

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 634
634:     def select_more(*columns)
635:       select(*((@opts[:select] || []) + columns))
636:     end

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 640
640:     def select_sql(opts = nil)
641:       opts = opts ? @opts.merge(opts) : @opts
642:       return static_sql(opts[:sql]) if opts[:sql]
643:       sql = 'SELECT'
644:       select_clause_order.each{|x| send("select_#{x}_sql", sql, opts)}
645:       sql
646:     end

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.

[Source]

     # File lib/sequel_core/dataset.rb, line 265
265:     def server(servr)
266:       clone(:server=>servr)
267:     end

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

[Source]

     # File lib/sequel_core/dataset.rb, line 271
271:     def set(*args)
272:       update(*args)
273:     end

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

[Source]

     # File lib/sequel_core/dataset.rb, line 277
277:     def set_defaults(hash)
278:       clone(:defaults=>(@opts[:defaults]||{}).merge(hash))
279:     end

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.

[Source]

     # File lib/sequel_core/object_graph.rb, line 158
158:     def set_graph_aliases(graph_aliases)
159:       ds = select(*graph_alias_columns(graph_aliases))
160:       ds.opts[:graph_aliases] = graph_aliases
161:       ds
162:     end

Associates or disassociates the dataset with a model(s). If nil is specified, the dataset is turned into a naked dataset and returns records as hashes. If a model class specified, the dataset is modified to return records as instances of the model class, e.g:

  class MyModel
    def initialize(values)
      @values = values
      ...
    end
  end

  dataset.set_model(MyModel)

You can also provide additional arguments to be passed to the model‘s initialize method:

  class MyModel
    def initialize(values, options)
      @values = values
      ...
    end
  end

  dataset.set_model(MyModel, :allow_delete => false)

The dataset can be made polymorphic by specifying a column name as the polymorphic key and a hash mapping column values to model classes.

  dataset.set_model(:kind, {1 => Person, 2 => Business})

You can also set a default model class to fall back on by specifying a class corresponding to nil:

  dataset.set_model(:kind, {nil => DefaultClass, 1 => Person, 2 => Business})

To make sure that there is always a default model class, the hash provided should have a default value. To make the dataset map string values to model classes, and keep a good default, try:

  dataset.set_model(:kind, Hash.new{|h,k| h[k] = (k.constantize rescue DefaultClass)})

[Source]

     # File lib/sequel_core/dataset.rb, line 322
322:     def set_model(key, *args)
323:       # This code is more verbose then necessary for performance reasons
324:       case key
325:       when nil # set_model(nil) => no argument provided, so the dataset is denuded
326:         @opts.merge!(:naked => true, :models => nil, :polymorphic_key => nil)
327:         self.row_proc = nil
328:       when Class
329:         # isomorphic model
330:         @opts.merge!(:naked => nil, :models => {nil => key}, :polymorphic_key => nil)
331:         if key.respond_to?(:load)
332:           # the class has a values setter method, so we use it
333:           self.row_proc = proc{|h| key.load(h, *args)}
334:         else
335:           # otherwise we just pass the hash to the constructor
336:           self.row_proc = proc{|h| key.new(h, *args)}
337:         end
338:       when Symbol
339:         # polymorphic model
340:         hash = args.shift || raise(ArgumentError, "No class hash supplied for polymorphic model")
341:         @opts.merge!(:naked => true, :models => hash, :polymorphic_key => key)
342:         if (hash.empty? ? (hash[nil] rescue nil) : hash.values.first).respond_to?(:load)
343:           # the class has a values setter method, so we use it
344:           self.row_proc = proc do |h|
345:             c = hash[h[key]] || hash[nil] || \
346:               raise(Error, "No matching model class for record (#{polymorphic_key} => #{h[polymorphic_key].inspect})")
347:             c.load(h, *args)
348:           end
349:         else
350:           # otherwise we just pass the hash to the constructor
351:           self.row_proc = proc do |h|
352:             c = hash[h[key]] || hash[nil] || \
353:               raise(Error, "No matching model class for record (#{polymorphic_key} => #{h[polymorphic_key].inspect})")
354:             c.new(h, *args)
355:           end
356:         end
357:       else
358:         raise ArgumentError, "Invalid model specified"
359:       end
360:       self
361:     end

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

[Source]

     # File lib/sequel_core/dataset.rb, line 365
365:     def set_overrides(hash)
366:       clone(:overrides=>hash.merge(@opts[:overrides]||{}))
367:     end

Returns the first record in the dataset.

[Source]

     # File lib/sequel_core/dataset/convenience.rb, line 179
179:     def single_record(opts = nil)
180:       each((opts||{}).merge(:limit=>1)){|r| return r}
181:       nil
182:     end

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

[Source]

     # File lib/sequel_core/dataset/convenience.rb, line 186
186:     def single_value(opts = nil)
187:       if r = single_record((opts||{}).merge(:graph=>false, :naked=>true))
188:         r.values.first
189:       end
190:     end
size()

Alias for count

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 649
649:     def sql(*args)
650:       select_sql(*args)
651:     end

SQL fragment for specifying subscripts (SQL arrays)

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 654
654:     def subscript_sql(s)
655:       "#{s.f}[#{s.sub.join(COMMA_SEPARATOR)}]"
656:     end

Returns the sum for the given column.

[Source]

     # File lib/sequel_core/dataset/convenience.rb, line 193
193:     def sum(column)
194:       get(SQL::Function.new(:sum, column))
195:     end

Converts a symbol into a column name. This method supports underscore notation in order to express qualified (two underscores) and aliased (three underscores) columns:

  ds = DB[:items]
  :abc.to_column_ref(ds) #=> "abc"
  :abc___a.to_column_ref(ds) #=> "abc AS a"
  :items__abc.to_column_ref(ds) #=> "items.abc"
  :items__abc___a.to_column_ref(ds) #=> "items.abc AS a"

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 668
668:     def symbol_to_column_ref(sym)
669:       c_table, column, c_alias = split_symbol(sym)
670:       qc = "#{"#{quote_identifier(c_table)}." if c_table}#{quote_identifier(column)}"
671:       c_alias ? as_sql(qc, c_alias) : qc
672:     end

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.

[Source]

     # File lib/sequel_core/dataset/convenience.rb, line 200
200:     def table_exists?
201:       raise(Sequel::Error, "this dataset has fixed SQL") if @opts[:sql]
202:       raise(Sequel::Error, "this dataset selects from multiple sources") if @opts[:from].size != 1
203:       t = @opts[:from].first
204:       raise(Sequel::Error, "this dataset selects from a sub query") if t.is_a?(Dataset)
205:       @db.table_exists?(t)
206:     end

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.

[Source]

     # File lib/sequel_core/dataset/convenience.rb, line 216
216:     def to_csv(include_column_titles = true)
217:       n = naked
218:       cols = n.columns
219:       csv = ''
220:       csv << "#{cols.join(COMMA_SEPARATOR)}\r\n" if include_column_titles
221:       n.each{|r| csv << "#{cols.collect{|c| r[c]}.join(COMMA_SEPARATOR)}\r\n"}
222:       csv
223:     end

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.

[Source]

     # File lib/sequel_core/dataset/convenience.rb, line 229
229:     def to_hash(key_column, value_column = nil)
230:       inject({}) do |m, r|
231:         m[r[key_column]] = value_column ? r[value_column] : r
232:         m
233:       end
234:     end

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.

[Source]

     # File lib/sequel_core/dataset.rb, line 389
389:     def transform(t)
390:       @transform = t
391:       t.each do |k, v|
392:         case v
393:         when Array
394:           if (v.size != 2) || !v.first.is_a?(Proc) && !v.last.is_a?(Proc)
395:             raise Error::InvalidTransform, "Invalid transform specified"
396:           end
397:         else
398:           unless v = STOCK_TRANSFORMS[v]
399:             raise Error::InvalidTransform, "Invalid transform specified"
400:           else
401:             t[k] = v
402:           end
403:         end
404:       end
405:       self
406:     end

Applies the value transform for data loaded from the database.

[Source]

     # File lib/sequel_core/dataset.rb, line 409
409:     def transform_load(r)
410:       r.inject({}) do |m, kv|
411:         k, v = *kv
412:         m[k] = (tt = @transform[k]) ? tt[0][v] : v
413:         m
414:       end
415:     end

Applies the value transform for data saved to the database.

[Source]

     # File lib/sequel_core/dataset.rb, line 418
418:     def transform_save(r)
419:       r.inject({}) do |m, kv|
420:         k, v = *kv
421:         m[k] = (tt = @transform[k]) ? tt[1][v] : v
422:         m
423:       end
424:     end

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

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 675
675:     def unfiltered
676:       clone(:where => nil, :having => nil)
677:     end

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"

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 684
684:     def union(dataset, all = false)
685:       compound_clone(:union, dataset, all)
686:     end

Returns a copy of the dataset with the distinct option.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 689
689:     def uniq(*args)
690:       clone(:distinct => args)
691:     end

Returns a copy of the dataset with no order.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 695
695:     def unordered
696:       order(nil)
697:     end

[Source]

     # File lib/sequel_core/dataset.rb, line 426
426:     def upcase_identifiers=(v)
427:       @identifier_input_method = v ? :upcase : nil
428:     end

Whether this dataset upcases identifiers.

[Source]

     # File lib/sequel_core/dataset.rb, line 431
431:     def upcase_identifiers?
432:       @identifier_input_method == :upcase
433:     end

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

[Source]

     # File lib/sequel_core/dataset.rb, line 437
437:     def update(*args)
438:       execute_dui(update_sql(*args))
439:     end

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.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 708
708:     def update_sql(values = {}, opts = nil)
709:       opts = opts ? @opts.merge(opts) : @opts
710: 
711:       return static_sql(opts[:sql]) if opts[:sql]
712: 
713:       if opts[:group]
714:         raise Error::InvalidOperation, "A grouped dataset cannot be updated"
715:       elsif (opts[:from].size > 1) or opts[:join]
716:         raise Error::InvalidOperation, "A joined dataset cannot be updated"
717:       end
718:       
719:       sql = "UPDATE #{source_list(@opts[:from])} SET "
720:       set = if values.is_a?(Hash)
721:         values = opts[:defaults].merge(values) if opts[:defaults]
722:         values = values.merge(opts[:overrides]) if opts[:overrides]
723:         # get values from hash
724:         values = transform_save(values) if @transform
725:         values.map do |k, v|
726:           "#{k.is_one_of?(String, Symbol) ? quote_identifier(k) : literal(k)} = #{literal(v)}"
727:         end.join(COMMA_SEPARATOR)
728:       else
729:         # copy values verbatim
730:         values
731:       end
732:       sql << set
733:       if where = opts[:where]
734:         sql << " WHERE #{literal(where)}"
735:       end
736: 
737:       sql
738:     end
where(*cond, &block)

Alias for filter

Protected Instance methods

Return true if the dataset has a non-nil value for any key in opts.

[Source]

     # File lib/sequel_core/dataset.rb, line 447
447:     def options_overlap(opts)
448:       !(@opts.collect{|k,v| k unless v.nil?}.compact & opts).empty?
449:     end

Return a cloned copy of the current dataset extended with PreparedStatementMethods, setting the type and modify values.

[Source]

     # File lib/sequel_core/dataset/prepared_statements.rb, line 204
204:     def to_prepared_statement(type, values=nil)
205:       ps = clone
206:       ps.extend(PreparedStatementMethods)
207:       ps.prepared_type = type
208:       ps.prepared_modify_values = values
209:       ps
210:     end

Returns a table reference for use in the FROM clause. Returns an SQL subquery frgament with an optional table alias.

[Source]

     # File lib/sequel_core/dataset/sql.rb, line 749
749:     def to_table_reference(table_alias=nil)
750:       s = "(#{sql})"
751:       table_alias ? as_sql(s, table_alias) : s
752:     end

[Validate]