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.
| COLUMN_CHANGE_OPTS | = | [:select, :sql, :from, :join].freeze | The dataset options that require the removal of cached columns if changed. | |
| MUTATION_METHODS | = | %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} | All methods that should have a ! method added that modifies the receiver. | |
| NON_SQL_OPTIONS | = | [:server, :defaults, :overrides] | Which options don‘t affect the SQL generation. Used by simple_select_all? to determine if this is a simple SELECT * FROM table. | |
| NOTIMPL_MSG | = | "This method must be overridden in Sequel adapters".freeze | ||
| WITH_SUPPORTED | = | :select_with_sql | ||
| 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 | ||
| CONDITIONED_JOIN_TYPES | = | [:inner, :full_outer, :right_outer, :left_outer, :full, :right, :left] | These symbols have _join methods created (e.g. inner_join) that call join_table with the symbol, passing along the arguments and block from the method call. | |
| UNCONDITIONED_JOIN_TYPES | = | [:natural, :natural_left, :natural_right, :natural_full, :cross] | These symbols have _join methods created (e.g. natural_join) that call join_table with the symbol. They only accept a single table argument which is passed to join_table, and they raise an error if called with a block. | |
| 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 | ||
| 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 | ||
| 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 | ||
| FROM_SELF_KEEP_OPTS | = | [:graph, :eager_graph, :graph_aliases] |
| inner_join | -> | join |
| convert_types | [RW] | Whether to convert some Java types to ruby types when retrieving rows. Uses the database‘s setting by default, can be set to false to roughly double performance when fetching rows. |
| 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 each to return. |
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.
# File lib/sequel/dataset.rb, line 91
91: def self.def_mutation_method(*meths)
92: meths.each do |meth|
93: class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end", __FILE__, __LINE__)
94: end
95: end
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.
# File lib/sequel/dataset.rb, line 77
77: def initialize(db, opts = nil)
78: @db = db
79: @quote_identifiers = db.quote_identifiers? if db.respond_to?(:quote_identifiers?)
80: @identifier_input_method = db.identifier_input_method if db.respond_to?(:identifier_input_method)
81: @identifier_output_method = db.identifier_output_method if db.respond_to?(:identifier_output_method)
82: @opts = opts || {}
83: @row_proc = nil
84: end
Returns the first record matching the conditions. Examples:
ds[:id=>1] => {:id=1}
# File lib/sequel/dataset/convenience.rb, line 13
13: def [](*conditions)
14: raise(Error, ARRAY_ACCESS_ERROR_MSG) if (conditions.length == 1 and conditions.first.is_a?(Integer)) or conditions.length == 0
15: first(*conditions)
16: end
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.
# File lib/sequel/dataset/graph.rb, line 6
6: def add_graph_aliases(graph_aliases)
7: ds = select_more(*graph_alias_columns(graph_aliases))
8: ds.opts[:graph_aliases] = (ds.opts[:graph_aliases] || ds.opts[:graph][:column_aliases] || {}).merge(graph_aliases)
9: ds
10: 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.
ds.filter(:a).and(:b) # SQL: WHERE a AND b
# File lib/sequel/dataset/query.rb, line 11
11: def and(*cond, &block)
12: raise(InvalidOperation, "No existing filter found.") unless @opts[:having] || @opts[:where]
13: filter(*cond, &block)
14: end
Returns the average value for the given column.
# File lib/sequel/dataset/convenience.rb, line 27
27: def avg(column)
28: aggregate_dataset.get{avg(column)}
29: end
Set the bind variables to use for the call. If bind variables have already been set for this dataset, they are updated with the contents of bind_vars.
# File lib/sequel/dataset/prepared_statements.rb, line 173
173: def bind(bind_vars={})
174: clone(:bind_vars=>@opts[:bind_vars] ? @opts[:bind_vars].merge(bind_vars) : bind_vars)
175: 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.
# File lib/sequel/dataset/prepared_statements.rb, line 182
182: def call(type, bind_variables={}, *values, &block)
183: prepare(type, nil, *values).call(bind_variables, &block)
184: end
SQL fragment for specifying given CaseExpression.
# File lib/sequel/dataset/sql.rb, line 56
56: def case_expression_sql(ce)
57: sql = '(CASE '
58: sql << "#{literal(ce.expression)} " if ce.expression
59: ce.conditions.collect{ |c,r|
60: sql << "WHEN #{literal(c)} THEN #{literal(r)} "
61: }
62: sql << "ELSE #{literal(ce.default)} END)"
63: 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.
# File lib/sequel/dataset.rb, line 109
109: def clone(opts = {})
110: c = super()
111: c.opts = @opts.merge(opts)
112: c.instance_variable_set(:@columns, nil) if opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
113: c
114: end
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.
# File lib/sequel/dataset/actions.rb, line 29
29: def columns
30: return @columns if @columns
31: ds = unfiltered.unordered.clone(:distinct => nil, :limit => 1)
32: ds.each{break}
33: @columns = ds.instance_variable_get(:@columns)
34: @columns || []
35: end
SQL fragment for complex expressions
# File lib/sequel/dataset/sql.rb, line 76
76: def complex_expression_sql(op, args)
77: case op
78: when *IS_OPERATORS
79: r = args.at(1)
80: if r.nil? || supports_is_true?
81: raise(InvalidOperation, 'Invalid argument used for IS operator') unless v = IS_LITERALS[r]
82: "(#{literal(args.at(0))} #{op} #{v})"
83: elsif op == :IS
84: complex_expression_sql("=""=", args)
85: else
86: complex_expression_sql(:OR, [SQL::BooleanExpression.new("!=""!=", *args), SQL::BooleanExpression.new(:IS, args.at(0), nil)])
87: end
88: when :IN, "NOT IN""NOT IN"
89: cols = args.at(0)
90: if !supports_multiple_column_in? && cols.is_a?(Array)
91: expr = SQL::BooleanExpression.new(:OR, *args.at(1).to_a.map{|vals| SQL::BooleanExpression.from_value_pairs(cols.zip(vals).map{|col, val| [col, val]})})
92: literal(op == :IN ? expr : ~expr)
93: else
94: "(#{literal(cols)} #{op} #{literal(args.at(1))})"
95: end
96: when *TWO_ARITY_OPERATORS
97: "(#{literal(args.at(0))} #{op} #{literal(args.at(1))})"
98: when *N_ARITY_OPERATORS
99: "(#{args.collect{|a| literal(a)}.join(" #{op} ")})"
100: when :NOT
101: "NOT #{literal(args.at(0))}"
102: when :NOOP
103: literal(args.at(0))
104: when 'B~''B~'
105: "~#{literal(args.at(0))}"
106: else
107: raise(InvalidOperation, "invalid operator #{op}")
108: end
109: end
Returns the number of records in the dataset.
# File lib/sequel/dataset/sql.rb, line 117
117: def count
118: aggregate_dataset.get{COUNT(:*){}.as(count)}.to_i
119: end
Add a mutation method to this dataset instance.
# File lib/sequel/dataset.rb, line 117
117: def def_mutation_method(*meths)
118: meths.each do |meth|
119: instance_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end", __FILE__, __LINE__)
120: end
121: end
Deletes the records in the dataset. The returned value is generally the number of records deleted, but that is adapter dependent. See delete_sql.
# File lib/sequel/dataset/actions.rb, line 46
46: def delete
47: execute_dui(delete_sql)
48: 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)"
# File lib/sequel/dataset/sql.rb, line 125
125: def delete_sql
126: return static_sql(opts[:sql]) if opts[:sql]
127: check_modification_allowed!
128: clause_sql(:delete)
129: end
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
# File lib/sequel/dataset/query.rb, line 25
25: def distinct(*args)
26: raise(InvalidOperation, "DISTINCT ON not supported") if !args.empty? && !supports_distinct_on?
27: clone(:distinct => args)
28: end
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.
# File lib/sequel/dataset/actions.rb, line 56
56: def each(&block)
57: if @opts[:graph]
58: graph_each(&block)
59: else
60: if row_proc = @row_proc
61: fetch_rows(select_sql){|r| yield row_proc.call(r)}
62: else
63: fetch_rows(select_sql, &block)
64: end
65: end
66: self
67: 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.
# File lib/sequel/extensions/pagination.rb, line 20
20: def each_page(page_size, &block)
21: raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
22: record_count = count
23: total_pages = (record_count / page_size.to_f).ceil
24: (1..total_pages).each{|page_no| yield paginate(page_no, page_size, record_count)}
25: self
26: end
Returns true if no records exist in the dataset, false otherwise
# File lib/sequel/dataset/convenience.rb, line 32
32: def empty?
33: get(1).nil?
34: end
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:
DB[:items].except(DB).sql #=> "SELECT * FROM items EXCEPT SELECT * FROM other_items"
# File lib/sequel/dataset/query.rb, line 40
40: def except(dataset, opts={})
41: opts = {:all=>opts} unless opts.is_a?(Hash)
42: raise(InvalidOperation, "EXCEPT not supported") unless supports_intersect_except?
43: raise(InvalidOperation, "EXCEPT ALL not supported") if opts[:all] && !supports_intersect_except_all?
44: compound_clone(:except, dataset, opts)
45: end
Performs the inverse of Dataset#filter.
dataset.exclude(:category => 'software').sql #=>
"SELECT * FROM items WHERE (category != 'software')"
# File lib/sequel/dataset/query.rb, line 51
51: def exclude(*cond, &block)
52: clause = (@opts[:having] ? :having : :where)
53: cond = cond.first if cond.size == 1
54: cond = filter_expr(cond, &block)
55: cond = SQL::BooleanExpression.invert(cond)
56: cond = SQL::BooleanExpression.new(:AND, @opts[clause], cond) if @opts[clause]
57: clone(clause => cond)
58: 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))"
# File lib/sequel/dataset/sql.rb, line 135
135: def exists
136: LiteralString.new("EXISTS (#{select_sql})")
137: end
Execute the SQL on the database and yield the rows as hashes with symbol keys.
# File lib/sequel/adapters/do.rb, line 182
182: def fetch_rows(sql)
183: execute(sql) do |reader|
184: cols = @columns = reader.fields.map{|f| output_identifier(f)}
185: while(reader.next!) do
186: h = {}
187: cols.zip(reader.values).each{|k, v| h[k] = v}
188: yield h
189: end
190: end
191: self
192: end
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:
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_filtering.rdoc for more examples and details.
# File lib/sequel/dataset/query.rb, line 107
107: def filter(*cond, &block)
108: _filter(@opts[:having] ? :having : :where, *cond, &block)
109: end
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}]
# File lib/sequel/dataset/convenience.rb, line 55
55: def first(*args, &block)
56: ds = block ? filter(&block) : self
57:
58: if args.empty?
59: ds.single_record
60: else
61: args = (args.size == 1) ? args.first : args
62: if Integer === args
63: ds.limit(args).all
64: else
65: ds.filter(args).single_record
66: end
67: end
68: 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 aliased name.
# File lib/sequel/dataset/sql.rb, line 141
141: def first_source_alias
142: source = @opts[:from]
143: if source.nil? || source.empty?
144: raise Error, 'No source specified for query'
145: end
146: case s = source.first
147: when SQL::AliasedExpression
148: s.aliaz
149: when Symbol
150: sch, table, aliaz = split_symbol(s)
151: aliaz ? aliaz.to_sym : s
152: else
153: s
154: end
155: end
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
# File lib/sequel/dataset/query.rb, line 116
116: def from(*source)
117: table_alias_num = 0
118: sources = []
119: source.each do |s|
120: case s
121: when Hash
122: s.each{|k,v| sources << SQL::AliasedExpression.new(k,v)}
123: when Dataset
124: sources << SQL::AliasedExpression.new(s, dataset_alias(table_alias_num+=1))
125: when Symbol
126: sch, table, aliaz = split_symbol(s)
127: if aliaz
128: s = sch ? SQL::QualifiedIdentifier.new(sch.to_sym, table.to_sym) : SQL::Identifier.new(table.to_sym)
129: sources << SQL::AliasedExpression.new(s, aliaz.to_sym)
130: else
131: sources << s
132: end
133: else
134: sources << s
135: end
136: end
137: o = {:from=>sources.empty? ? nil : sources}
138: o[:num_dataset_sources] = table_alias_num if table_alias_num > 0
139: clone(o)
140: end
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'"
# File lib/sequel/dataset/query.rb, line 149
149: def from_self(opts={})
150: fs = {}
151: @opts.keys.each{|k| fs[k] = nil unless FROM_SELF_KEEP_OPTS.include?(k)}
152: clone(fs).from(opts[:alias] ? as(opts[:alias]) : self)
153: end
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)}
# File lib/sequel/dataset/convenience.rb, line 75
75: def get(column=nil, &block)
76: if column
77: raise(Error, GET_ERROR_MSG) if block
78: select(column).single_value
79: else
80: select(&block).single_value
81: end
82: 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, :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:
# File lib/sequel/dataset/graph.rb, line 60
60: def graph(dataset, join_conditions = nil, options = {}, &block)
61: # Allow the use of a model, dataset, or symbol as the first argument
62: # Find the table name/dataset based on the argument
63: dataset = dataset.dataset if dataset.respond_to?(:dataset)
64: table_alias = options[:table_alias]
65: case dataset
66: when Symbol
67: table = dataset
68: dataset = @db[dataset]
69: table_alias ||= table
70: when ::Sequel::Dataset
71: if dataset.simple_select_all?
72: table = dataset.opts[:from].first
73: table_alias ||= table
74: else
75: table = dataset
76: table_alias ||= dataset_alias((@opts[:num_dataset_sources] || 0)+1)
77: end
78: else
79: raise Error, "The dataset argument should be a symbol, dataset, or model"
80: end
81:
82: # Raise Sequel::Error with explanation that the table alias has been used
83: raise_alias_error = lambda do
84: raise(Error, "this #{options[:table_alias] ? 'alias' : 'table'} has already been been used, please specify " \
85: "#{options[:table_alias] ? 'a different alias' : 'an alias via the :table_alias option'}")
86: end
87:
88: # Only allow table aliases that haven't been used
89: raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)
90:
91: # Use a from_self if this is already a joined table
92: ds = (!@opts[:graph] && (@opts[:from].length > 1 || @opts[:join])) ? from_self(:alias=>options[:from_self_alias] || first_source) : self
93:
94: # Join the table early in order to avoid cloning the dataset twice
95: ds = ds.join_table(options[:join_type] || :left_outer, table, join_conditions, :table_alias=>table_alias, :implicit_qualifier=>options[:implicit_qualifier], &block)
96: opts = ds.opts
97:
98: # Whether to include the table in the result set
99: add_table = options[:select] == false ? false : true
100: # Whether to add the columns to the list of column aliases
101: add_columns = !ds.opts.include?(:graph_aliases)
102:
103: # Setup the initial graph data structure if it doesn't exist
104: unless graph = opts[:graph]
105: master = ds.first_source_alias
106: raise_alias_error.call if master == table_alias
107: # Master hash storing all .graph related information
108: graph = opts[:graph] = {}
109: # Associates column aliases back to tables and columns
110: column_aliases = graph[:column_aliases] = {}
111: # Associates table alias (the master is never aliased)
112: table_aliases = graph[:table_aliases] = {master=>self}
113: # Keep track of the alias numbers used
114: ca_num = graph[:column_alias_num] = Hash.new(0)
115: # All columns in the master table are never
116: # aliased, but are not included if set_graph_aliases
117: # has been used.
118: if add_columns
119: select = opts[:select] = []
120: columns.each do |column|
121: column_aliases[column] = [master, column]
122: select.push(SQL::QualifiedIdentifier.new(master, column))
123: end
124: end
125: end
126:
127: # Add the table alias to the list of aliases
128: # Even if it isn't been used in the result set,
129: # we add a key for it with a nil value so we can check if it
130: # is used more than once
131: table_aliases = graph[:table_aliases]
132: table_aliases[table_alias] = add_table ? dataset : nil
133:
134: # Add the columns to the selection unless we are ignoring them
135: if add_table && add_columns
136: select = opts[:select]
137: column_aliases = graph[:column_aliases]
138: ca_num = graph[:column_alias_num]
139: # Which columns to add to the result set
140: cols = options[:select] || dataset.columns
141: # If the column hasn't been used yet, don't alias it.
142: # If it has been used, try table_column.
143: # If that has been used, try table_column_N
144: # using the next value of N that we know hasn't been
145: # used
146: cols.each do |column|
147: col_alias, identifier = if column_aliases[column]
148: column_alias = "#{table_alias}_#{column}""#{table_alias}_#{column}"
149: if column_aliases[column_alias]
150: column_alias_num = ca_num[column_alias]
151: column_alias = "#{column_alias}_#{column_alias_num}""#{column_alias}_#{column_alias_num}"
152: ca_num[column_alias] += 1
153: end
154: [column_alias, SQL::QualifiedIdentifier.new(table_alias, column).as(column_alias)]
155: else
156: [column, SQL::QualifiedIdentifier.new(table_alias, column)]
157: end
158: column_aliases[col_alias] = [table_alias, column]
159: select.push(identifier)
160: end
161: end
162: ds
163: 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.
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'
# File lib/sequel/dataset/query.rb, line 163
163: def grep(cols, terms)
164: filter(SQL::BooleanExpression.new(:OR, *Array(cols).collect{|c| SQL::StringExpression.like(c, *terms)}))
165: end
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
# File lib/sequel/dataset/query.rb, line 172
172: def group(*columns)
173: clone(:group => (columns.compact.empty? ? nil : columns))
174: end
Returns a dataset grouped by the given column with count by group, order by the count of records (in ascending order). Column aliases may be supplied, and will be included in the select clause.
Examples:
ds.group_and_count(:name).all => [{:name=>'a', :count=>1}, ...]
ds.group_and_count(:first_name, :last_name).all => [{:first_name=>'a', :last_name=>'b', :count=>1}, ...]
ds.group_and_count(:first_name___name).all => [{:name=>'a', :count=>1}, ...]
# File lib/sequel/dataset/convenience.rb, line 93
93: def group_and_count(*columns)
94: groups = columns.map do |c|
95: c_table, column, _ = split_symbol(c)
96: c_table ? column.to_sym.qualify(c_table) : column.to_sym
97: end
98: group(*groups).select(*(columns + [COUNT_OF_ALL_AS_COUNT])).order(:count)
99: end
Returns a copy of the dataset with the HAVING conditions changed. See filter for argument types.
dataset.group(:sum).having(:sum=>10) # SQL: SELECT * FROM items GROUP BY sum HAVING sum = 10
# File lib/sequel/dataset/query.rb, line 180
180: def having(*cond, &block)
181: _filter(:having, *cond, &block)
182: 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 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)
# File lib/sequel/dataset/convenience.rb, line 119
119: def import(columns, values, opts={})
120: return @db.transaction{insert(columns, values)} if values.is_a?(Dataset)
121:
122: return if values.empty?
123: raise(Error, IMPORT_ERROR_MSG) if columns.empty?
124:
125: if slice_size = opts[:commit_every] || opts[:slice]
126: offset = 0
127: loop do
128: @db.transaction(opts){multi_insert_sql(columns, values[offset, slice_size]).each{|st| execute_dui(st)}}
129: offset += slice_size
130: break if offset >= values.length
131: end
132: else
133: statements = multi_insert_sql(columns, values)
134: @db.transaction{statements.each{|st| execute_dui(st)}}
135: end
136: end
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.
# File lib/sequel/dataset/actions.rb, line 78
78: def insert(*values)
79: execute_insert(insert_sql(*values))
80: 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.
# File lib/sequel/dataset/sql.rb, line 168
168: def insert_multiple(array, &block)
169: if block
170: array.each {|i| insert(block[i])}
171: else
172: array.each {|i| insert(i)}
173: end
174: end
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
# File lib/sequel/dataset/sql.rb, line 192
192: def insert_sql(*values)
193: return static_sql(@opts[:sql]) if @opts[:sql]
194:
195: check_modification_allowed!
196:
197: columns = []
198:
199: case values.size
200: when 0
201: return insert_sql({})
202: when 1
203: case vals = values.at(0)
204: when Hash
205: vals = @opts[:defaults].merge(vals) if @opts[:defaults]
206: vals = vals.merge(@opts[:overrides]) if @opts[:overrides]
207: values = []
208: vals.each do |k,v|
209: columns << k
210: values << v
211: end
212: when Dataset, Array, LiteralString
213: values = vals
214: else
215: if vals.respond_to?(:values) && (v = vals.values).is_a?(Hash)
216: return insert_sql(v)
217: end
218: end
219: when 2
220: if (v0 = values.at(0)).is_a?(Array) && ((v1 = values.at(1)).is_a?(Array) || v1.is_a?(Dataset) || v1.is_a?(LiteralString))
221: columns, values = v0, v1
222: raise(Error, "Different number of values and columns given to insert_sql") if values.is_a?(Array) and columns.length != values.length
223: end
224: end
225:
226: columns = columns.map{|k| literal(String === k ? k.to_sym : k)}
227: clone(:columns=>columns, :values=>values)._insert_sql
228: end
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:
DB[:items].intersect(DB).sql #=> "SELECT * FROM items INTERSECT SELECT * FROM other_items"
# File lib/sequel/dataset/query.rb, line 194
194: def intersect(dataset, opts={})
195: opts = {:all=>opts} unless opts.is_a?(Hash)
196: raise(InvalidOperation, "INTERSECT not supported") unless supports_intersect_except?
197: raise(InvalidOperation, "INTERSECT ALL not supported") if opts[:all] && !supports_intersect_except_all?
198: compound_clone(:intersect, dataset, opts)
199: end
Inverts the current filter
dataset.filter(:category => 'software').invert.sql #=>
"SELECT * FROM items WHERE (category != 'software')"
# File lib/sequel/dataset/query.rb, line 205
205: def invert
206: having, where = @opts[:having], @opts[:where]
207: raise(Error, "No current filter") unless having || where
208: o = {}
209: o[:having] = SQL::BooleanExpression.invert(having) if having
210: o[:where] = SQL::BooleanExpression.invert(where) if where
211: clone(o)
212: end
SQL fragment specifying a JOIN clause without ON or USING.
# File lib/sequel/dataset/sql.rb, line 231
231: def join_clause_sql(jc)
232: table = jc.table
233: table_alias = jc.table_alias
234: table_alias = nil if table == table_alias
235: tref = table_ref(table)
236: " #{join_type_sql(jc.join_type)} #{table_alias ? as_sql(tref, table_alias) : tref}"
237: end
Returns a joined dataset. Uses the following arguments:
# File lib/sequel/dataset/sql.rb, line 279
279: def join_table(type, table, expr=nil, options={}, &block)
280: using_join = expr.is_a?(Array) && !expr.empty? && expr.all?{|x| x.is_a?(Symbol)}
281: if using_join && !supports_join_using?
282: h = {}
283: expr.each{|s| h[s] = s}
284: return join_table(type, table, h, options)
285: end
286:
287: if [Symbol, String].any?{|c| options.is_a?(c)}
288: table_alias = options
289: last_alias = nil
290: else
291: table_alias = options[:table_alias]
292: last_alias = options[:implicit_qualifier]
293: end
294: if Dataset === table
295: if table_alias.nil?
296: table_alias_num = (@opts[:num_dataset_sources] || 0) + 1
297: table_alias = dataset_alias(table_alias_num)
298: end
299: table_name = table_alias
300: else
301: table = table.table_name if table.respond_to?(:table_name)
302: table_name = table_alias || table
303: end
304:
305: join = if expr.nil? and !block_given?
306: SQL::JoinClause.new(type, table, table_alias)
307: elsif using_join
308: raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block_given?
309: SQL::JoinUsingClause.new(expr, type, table, table_alias)
310: else
311: last_alias ||= @opts[:last_joined_table] || first_source_alias
312: if Sequel.condition_specifier?(expr)
313: expr = expr.collect do |k, v|
314: k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
315: v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
316: [k,v]
317: end
318: end
319: if block_given?
320: expr2 = yield(table_name, last_alias, @opts[:join] || [])
321: expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
322: end
323: SQL::JoinOnClause.new(expr, type, table, table_alias)
324: end
325:
326: opts = {:join => (@opts[:join] || []) + [join], :last_joined_table => table_name}
327: opts[:num_dataset_sources] = table_alias_num if table_alias_num
328: clone(opts)
329: 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.
# File lib/sequel/dataset/convenience.rb, line 148
148: def last(*args, &block)
149: raise(Error, 'No order specified') unless @opts[:order]
150: reverse.first(*args, &block)
151: 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.
dataset.limit(10) # SQL: SELECT * FROM items LIMIT 10 dataset.limit(10, 20) # SQL: SELECT * FROM items LIMIT 10 OFFSET 20
# File lib/sequel/dataset/query.rb, line 220
220: def limit(l, o = nil)
221: return from_self.limit(l, o) if @opts[:sql]
222:
223: if Range === l
224: o = l.first
225: l = l.last - l.first + (l.exclude_end? ? 0 : 1)
226: end
227: l = l.to_i
228: raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
229: opts = {:limit => l}
230: if o
231: o = o.to_i
232: raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
233: opts[:offset] = o
234: end
235: clone(opts)
236: 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.
# File lib/sequel/dataset/sql.rb, line 341
341: def literal(v)
342: case v
343: when String
344: return v if v.is_a?(LiteralString)
345: v.is_a?(SQL::Blob) ? literal_blob(v) : literal_string(v)
346: when Symbol
347: literal_symbol(v)
348: when Integer
349: literal_integer(v)
350: when Hash
351: literal_hash(v)
352: when SQL::Expression
353: literal_expression(v)
354: when Float
355: literal_float(v)
356: when BigDecimal
357: literal_big_decimal(v)
358: when NilClass
359: NULL
360: when TrueClass
361: literal_true
362: when FalseClass
363: literal_false
364: when Array
365: literal_array(v)
366: when Time
367: literal_time(v)
368: when DateTime
369: literal_datetime(v)
370: when Date
371: literal_date(v)
372: when Dataset
373: literal_dataset(v)
374: else
375: literal_other(v)
376: end
377: end
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, ...]
# File lib/sequel/dataset/convenience.rb, line 159
159: def map(column=nil, &block)
160: if column
161: raise(Error, MAP_ERROR_MSG) if block
162: super(){|r| r[column]}
163: else
164: super(&block)
165: end
166: end
Returns the maximum value for the given column.
# File lib/sequel/dataset/convenience.rb, line 169
169: def max(column)
170: aggregate_dataset.get{max(column)}
171: end
Returns the minimum value for the given column.
# File lib/sequel/dataset/convenience.rb, line 174
174: def min(column)
175: aggregate_dataset.get{min(column)}
176: end
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.
# File lib/sequel/dataset/convenience.rb, line 188
188: def multi_insert(hashes, opts={})
189: return if hashes.empty?
190: columns = hashes.first.keys
191: import(columns, hashes.map{|h| columns.map{|c| h[c]}}, opts)
192: 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.
# File lib/sequel/dataset/sql.rb, line 385
385: def multi_insert_sql(columns, values)
386: values.map{|r| insert_sql(columns, r)}
387: end
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
# File lib/sequel/dataset/query.rb, line 242
242: def or(*cond, &block)
243: clause = (@opts[:having] ? :having : :where)
244: raise(InvalidOperation, "No existing filter found.") unless @opts[clause]
245: cond = cond.first if cond.size == 1
246: clone(clause => SQL::BooleanExpression.new(:OR, @opts[clause], filter_expr(cond, &block)))
247: 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. 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'
# File lib/sequel/dataset/query.rb, line 262
262: def order(*columns, &block)
263: columns += Array(Sequel.virtual_row(&block)) if block
264: clone(:order => (columns.compact.empty?) ? nil : columns)
265: end
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'
# File lib/sequel/dataset/query.rb, line 273
273: def order_more(*columns, &block)
274: columns = @opts[:order] + columns if @opts[:order]
275: order(*columns, &block)
276: 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.
# File lib/sequel/extensions/pagination.rb, line 11
11: def paginate(page_no, page_size, record_count=nil)
12: raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
13: paginated = limit(page_size, (page_no - 1) * page_size)
14: paginated.extend(Pagination)
15: paginated.set_pagination_info(page_no, page_size, record_count || count)
16: end
SQL fragment for a literal string with placeholders
# File lib/sequel/dataset/sql.rb, line 396
396: def placeholder_literal_string_sql(pls)
397: args = pls.args
398: s = if args.is_a?(Hash)
399: re = /:(#{args.keys.map{|k| Regexp.escape(k.to_s)}.join('|')})\b/
400: pls.str.gsub(re){literal(args[$1.to_sym])}
401: else
402: i = -1
403: pls.str.gsub(QUESTION_MARK){literal(args.at(i+=1))}
404: end
405: s = "(#{s})" if pls.parens
406: s
407: 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')
# File lib/sequel/dataset/prepared_statements.rb, line 195
195: def prepare(type, name=nil, *values)
196: ps = to_prepared_statement(type, values)
197: db.prepared_statements[name] = ps if name
198: ps
199: end
Create a named prepared statement that is stored in the database (and connection) for reuse.
# File lib/sequel/adapters/jdbc.rb, line 468
468: def prepare(type, name=nil, *values)
469: ps = to_prepared_statement(type, values)
470: ps.extend(PreparedStatementMethods)
471: if name
472: ps.prepared_statement_name = name
473: db.prepared_statements[name] = ps
474: end
475: ps
476: end
SQL fragment for the qualifed identifier, specifying a table and a column (or schema and table).
# File lib/sequel/dataset/sql.rb, line 411
411: def qualified_identifier_sql(qcr)
412: [qcr.table, qcr.column].map{|x| [SQL::QualifiedIdentifier, SQL::Identifier, Symbol].any?{|c| x.is_a?(c)} ? literal(x) : quote_identifier(x)}.join('.')
413: end
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.
# File lib/sequel/dataset/sql.rb, line 424
424: def qualify_to(table)
425: o = @opts
426: return clone if o[:sql]
427: h = {}
428: (o.keys & QUALIFY_KEYS).each do |k|
429: h[k] = qualified_expression(o[k], table)
430: end
431: h[:select] = [SQL::ColumnAll.new(table)] if !o[:select] || o[:select].empty?
432: clone(h)
433: end
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.
# File lib/sequel/dataset/sql.rb, line 440
440: def qualify_to_first_source
441: qualify_to(first_source)
442: 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.
# File lib/sequel/extensions/query.rb, line 30
30: def query(&block)
31: copy = clone({})
32: copy.extend(QueryBlockCopy)
33: copy.instance_eval(&block)
34: clone(copy.opts)
35: end
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.
# File lib/sequel/dataset/sql.rb, line 447
447: def quote_identifier(name)
448: return name if name.is_a?(LiteralString)
449: name = name.value if name.is_a?(SQL::Identifier)
450: name = input_identifier(name)
451: name = quoted_identifier(name) if quote_identifiers?
452: name
453: end
Whether this dataset quotes identifiers.
# File lib/sequel/dataset/features.rb, line 4 4: def quote_identifiers? 5: @quote_identifiers 6: end
Separates the schema from the table and returns a string with them quoted (if quoting identifiers)
# File lib/sequel/dataset/sql.rb, line 457
457: def quote_schema_table(table)
458: schema, table = schema_and_table(table)
459: "#{"#{quote_identifier(schema)}." if schema}#{quote_identifier(table)}"
460: 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).
# File lib/sequel/dataset/sql.rb, line 465
465: def quoted_identifier(name)
466: "\"#{name.to_s.gsub('"', '""')}\""
467: end
Split the schema information from the table
# File lib/sequel/dataset/sql.rb, line 470
470: def schema_and_table(table_name)
471: sch = db.default_schema if db
472: case table_name
473: when Symbol
474: s, t, a = split_symbol(table_name)
475: [s||sch, t]
476: when SQL::QualifiedIdentifier
477: [table_name.table, table_name.column]
478: when SQL::Identifier
479: [sch, table_name.value]
480: when String
481: [sch, table_name]
482: else
483: raise Error, 'table_name should be a Symbol, SQL::QualifiedIdentifier, SQL::Identifier, or String'
484: end
485: end
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
# File lib/sequel/dataset/query.rb, line 292
292: def select(*columns, &block)
293: columns += Array(Sequel.virtual_row(&block)) if block
294: m = []
295: columns.map do |i|
296: i.is_a?(Hash) ? m.concat(i.map{|k, v| SQL::AliasedExpression.new(k,v)}) : m << i
297: end
298: clone(:select => m)
299: end
Returns a copy of the dataset selecting the wildcard.
dataset.select(:a).select_all # SELECT * FROM items
# File lib/sequel/dataset/query.rb, line 304
304: def select_all
305: clone(:select => nil)
306: end
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
# File lib/sequel/dataset/query.rb, line 313
313: def select_more(*columns, &block)
314: columns = @opts[:select] + columns if @opts[:select]
315: select(*columns, &block)
316: end
Formats a SELECT statement
dataset.select_sql # => "SELECT * FROM items"
# File lib/sequel/dataset/sql.rb, line 490
490: def select_sql
491: return static_sql(@opts[:sql]) if @opts[:sql]
492: clause_sql(:select)
493: 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 (which is SELECT uses :read_only database and all other queries use the :default database).
# File lib/sequel/dataset.rb, line 140
140: def server(servr)
141: clone(:server=>servr)
142: 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], :forty_two=>[:albums, :fourtwo, 42]).first
=> {:artists=>{:name=>artists.name}, :albums=>{:name=>albums.name, :fourtwo=>42}}
Arguments:
# File lib/sequel/dataset/graph.rb, line 182
182: def set_graph_aliases(graph_aliases)
183: ds = select(*graph_alias_columns(graph_aliases))
184: ds.opts[:graph_aliases] = graph_aliases
185: ds
186: end
Same as select_sql, not aliased directly to make subclassing simpler.
# File lib/sequel/dataset/sql.rb, line 496
496: def sql
497: select_sql
498: end
Whether the dataset supports common table expressions (the WITH clause).
# File lib/sequel/dataset/features.rb, line 15
15: def supports_cte?
16: select_clause_methods.include?(WITH_SUPPORTED)
17: end
Whether the dataset supports the DISTINCT ON clause, true by default.
# File lib/sequel/dataset/features.rb, line 20
20: def supports_distinct_on?
21: true
22: end
Whether the dataset supports the IS TRUE syntax.
# File lib/sequel/dataset/features.rb, line 35
35: def supports_is_true?
36: true
37: end
Whether the dataset supports the JOIN table USING (column1, …) syntax.
# File lib/sequel/dataset/features.rb, line 40
40: def supports_join_using?
41: true
42: end
Whether the dataset supports window functions.
# File lib/sequel/dataset/features.rb, line 61
61: def supports_window_functions?
62: false
63: 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 shouldn‘t use this.
# File lib/sequel/dataset/convenience.rb, line 229
229: def to_csv(include_column_titles = true)
230: n = naked
231: cols = n.columns
232: csv = ''
233: csv << "#{cols.join(COMMA_SEPARATOR)}\r\n" if include_column_titles
234: n.each{|r| csv << "#{cols.collect{|c| r[c]}.join(COMMA_SEPARATOR)}\r\n"}
235: csv
236: 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.
# File lib/sequel/dataset/convenience.rb, line 242
242: def to_hash(key_column, value_column = nil)
243: inject({}) do |m, r|
244: m[r[key_column]] = value_column ? r[value_column] : r
245: m
246: end
247: end
Truncates the dataset. Returns nil.
# File lib/sequel/dataset/actions.rb, line 89
89: def truncate
90: execute_ddl(truncate_sql)
91: end
SQL query to truncate the table
# File lib/sequel/dataset/sql.rb, line 506
506: def truncate_sql
507: if opts[:sql]
508: static_sql(opts[:sql])
509: else
510: check_modification_allowed!
511: raise(InvalidOperation, "Can't truncate filtered datasets") if opts[:where]
512: _truncate_sql(source_list(opts[:from]))
513: end
514: end
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:
DB[:items].union(DB).sql #=> "SELECT * FROM items UNION SELECT * FROM other_items"
# File lib/sequel/dataset/query.rb, line 341
341: def union(dataset, opts={})
342: opts = {:all=>opts} unless opts.is_a?(Hash)
343: compound_clone(:union, dataset, opts)
344: end
Updates values for the dataset. The returned value is generally the number of rows updated, but that is adapter dependent. See update_sql.
# File lib/sequel/dataset/actions.rb, line 95
95: def update(values={})
96: execute_dui(update_sql(values))
97: end
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.
# File lib/sequel/dataset/sql.rb, line 523
523: def update_sql(values = {})
524: return static_sql(opts[:sql]) if opts[:sql]
525: check_modification_allowed!
526: clone(:values=>values)._update_sql
527: end
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
# File lib/sequel/dataset/sql.rb, line 533
533: def where(*cond, &block)
534: _filter(:where, *cond, &block)
535: end
The SQL fragment for the given window‘s options.
# File lib/sequel/dataset/sql.rb, line 538
538: def window_sql(opts)
539: raise(Error, 'This dataset does not support window functions') unless supports_window_functions?
540: window = literal(opts[:window]) if opts[:window]
541: partition = "PARTITION BY #{expression_list(Array(opts[:partition]))}" if opts[:partition]
542: order = "ORDER BY #{expression_list(Array(opts[:order]))}" if opts[:order]
543: frame = case opts[:frame]
544: when nil
545: nil
546: when :all
547: "ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING"
548: when :rows
549: "ROWS UNBOUNDED PRECEDING"
550: else
551: raise Error, "invalid window frame clause, should be :all, :rows, or nil"
552: end
553: "(#{[window, partition, order, frame].compact.join(' ')})"
554: end
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:
# File lib/sequel/dataset/sql.rb, line 566
566: def with(name, dataset, opts={})
567: raise(Error, 'This datatset does not support common table expressions') unless supports_cte?
568: clone(:with=>(@opts[:with]||[]) + [opts.merge(:name=>name, :dataset=>dataset)])
569: end
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:
# File lib/sequel/dataset/sql.rb, line 576
576: def with_recursive(name, nonrecursive, recursive, opts={})
577: raise(Error, 'This datatset does not support common table expressions') unless supports_cte?
578: clone(:with=>(@opts[:with]||[]) + [opts.merge(:recursive=>true, :name=>name, :dataset=>nonrecursive.union(recursive, {:all=>opts[:union_all] != false, :from_self=>false}))])
579: end
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
# File lib/sequel/dataset/sql.rb, line 585
585: def with_sql(sql, *args)
586: sql = SQL::PlaceholderLiteralString.new(sql, args) unless args.empty?
587: clone(:sql=>sql)
588: end
Formats an UPDATE statement using the stored values.
# File lib/sequel/dataset/sql.rb, line 606
606: def _update_sql
607: clause_sql(:update)
608: end
Return true if the dataset has a non-nil value for any key in opts.
# File lib/sequel/dataset.rb, line 162
162: def options_overlap(opts)
163: !(@opts.collect{|k,v| k unless v.nil?}.compact & opts).empty?
164: end
Whether this dataset is a simple SELECT * FROM table.
# File lib/sequel/dataset.rb, line 167
167: def simple_select_all?
168: o = @opts.reject{|k,v| v.nil? || NON_SQL_OPTIONS.include?(k)}
169: o.length == 1 && (f = o[:from]) && f.length == 1 && f.first.is_a?(Symbol)
170: end
Return a cloned copy of the current dataset extended with PreparedStatementMethods, setting the type and modify values.
# File lib/sequel/dataset/prepared_statements.rb, line 205
205: def to_prepared_statement(type, values=nil)
206: ps = bind
207: ps.extend(PreparedStatementMethods)
208: ps.prepared_type = type
209: ps.prepared_modify_values = values
210: ps
211: end