1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
|
module ActiveRecord
module Calculations #:nodoc:
CALCULATIONS_OPTIONS = [:conditions, :joins, :order, :select, :group, :having, :distinct, :limit, :offset, :include]
def self.included(base)
base.extend(ClassMethods)
end
module ClassMethods
# Count operates using three different approaches.
#
# * Count all: By not passing any parameters to count, it will return a count of all the rows for the model.
# * Count using column : By passing a column name to count, it will return a count of all the rows for the model with supplied column present
# * Count using options will find the row count matched by the options used.
#
# The third approach, count using options, accepts an option hash as the only parameter. The options are:
#
# * <tt>:conditions</tt>: An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro.
# * <tt>:joins</tt>: Either an SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id" (rarely needed)
# or named associations in the same form used for the :include option, which will perform an INNER JOIN on the associated table(s).
# If the value is a string, then the records will be returned read-only since they will have attributes that do not correspond to the table's columns.
# Pass :readonly => false to override.
# * <tt>:include</tt>: Named associations that should be loaded alongside using LEFT OUTER JOINs. The symbols named refer
# to already defined associations. When using named associations, count returns the number of DISTINCT items for the model you're counting.
# See eager loading under Associations.
# * <tt>:order</tt>: An SQL fragment like "created_at DESC, name" (really only used with GROUP BY calculations).
# * <tt>:group</tt>: An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause.
# * <tt>:select</tt>: By default, this is * as in SELECT * FROM, but can be changed if you, for example, want to do a join but not
# include the joined columns.
# * <tt>:distinct</tt>: Set this to true to make this a distinct calculation, such as SELECT COUNT(DISTINCT posts.id) ...
#
# Examples for counting all:
# Person.count # returns the total count of all people
#
# Examples for counting by column:
# Person.count(:age) # returns the total count of all people whose age is present in database
#
# Examples for count with options:
# Person.count(:conditions => "age > 26")
# Person.count(:conditions => "age > 26 AND job.salary > 60000", :include => :job) # because of the named association, it finds the DISTINCT count using LEFT OUTER JOIN.
# Person.count(:conditions => "age > 26 AND job.salary > 60000", :joins => "LEFT JOIN jobs on jobs.person_id = person.id") # finds the number of rows matching the conditions and joins.
# Person.count('id', :conditions => "age > 26") # Performs a COUNT(id)
# Person.count(:all, :conditions => "age > 26") # Performs a COUNT(*) (:all is an alias for '*')
#
# Note: Person.count(:all) will not work because it will use :all as the condition. Use Person.count instead.
def count(*args)
calculate(:count, *construct_count_options_from_args(*args))
end
# Calculates the average value on a given column. The value is returned as a float. See #calculate for examples with options.
#
# Person.average('age')
def average(column_name, options = {})
calculate(:avg, column_name, options)
end
# Calculates the minimum value on a given column. The value is returned with the same data type of the column. See #calculate for examples with options.
#
# Person.minimum('age')
def minimum(column_name, options = {})
calculate(:min, column_name, options)
end
# Calculates the maximum value on a given column. The value is returned with the same data type of the column. See #calculate for examples with options.
#
# Person.maximum('age')
def maximum(column_name, options = {})
calculate(:max, column_name, options)
end
# Calculates the sum of values on a given column. The value is returned with the same data type of the column. See #calculate for examples with options.
#
# Person.sum('age')
def sum(column_name, options = {})
calculate(:sum, column_name, options)
end
# This calculates aggregate values in the given column. Methods for count, sum, average, minimum, and maximum have been added as shortcuts.
# Options such as :conditions, :order, :group, :having, and :joins can be passed to customize the query.
#
# There are two basic forms of output:
# * Single aggregate value: The single value is type cast to Fixnum for COUNT, Float for AVG, and the given column's type for everything else.
# * Grouped values: This returns an ordered hash of the values and groups them by the :group option. It takes either a column name, or the name
# of a belongs_to association.
#
# values = Person.maximum(:age, :group => 'last_name')
# puts values["Drake"]
# => 43
#
# drake = Family.find_by_last_name('Drake')
# values = Person.maximum(:age, :group => :family) # Person belongs_to :family
# puts values[drake]
# => 43
#
# values.each do |family, max_age|
# ...
# end
#
# Options:
# * <tt>:conditions</tt> - An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro.
# * <tt>:include</tt>: Eager loading, see Associations for details. Since calculations don't load anything, the purpose of this is to access fields on joined tables in your conditions, order, or group clauses.
# * <tt>:joins</tt> - An SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id". (Rarely needed).
# The records will be returned read-only since they will have attributes that do not correspond to the table's columns.
# * <tt>:order</tt> - An SQL fragment like "created_at DESC, name" (really only used with GROUP BY calculations).
# * <tt>:group</tt> - An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause.
# * <tt>:select</tt> - By default, this is * as in SELECT * FROM, but can be changed if you for example want to do a join, but not
# include the joined columns.
# * <tt>:distinct</tt> - Set this to true to make this a distinct calculation, such as SELECT COUNT(DISTINCT posts.id) ...
#
# Examples:
# Person.calculate(:count, :all) # The same as Person.count
# Person.average(:age) # SELECT AVG(age) FROM people...
# Person.minimum(:age, :conditions => ['last_name != ?', 'Drake']) # Selects the minimum age for everyone with a last name other than 'Drake'
# Person.minimum(:age, :having => 'min(age) > 17', :group => :last_name) # Selects the minimum age for any family without any minors
def calculate(operation, column_name, options = {})
validate_calculation_options(operation, options)
column_name = options[:select] if options[:select]
column_name = '*' if column_name == :all
column = column_for column_name
catch :invalid_query do
if options[:group]
return execute_grouped_calculation(operation, column_name, column, options)
else
return execute_simple_calculation(operation, column_name, column, options)
end
end
0
end
protected
def construct_count_options_from_args(*args)
options = {}
column_name = :all
# We need to handle
# count()
# count(:column_name=:all)
# count(options={})
# count(column_name=:all, options={})
case args.size
when 1
args[0].is_a?(Hash) ? options = args[0] : column_name = args[0]
when 2
column_name, options = args
else
raise ArgumentError, "Unexpected parameters passed to count(): #{args.inspect}"
end if args.size > 0
[column_name, options]
end
def construct_calculation_sql(operation, column_name, options) #:nodoc:
operation = operation.to_s.downcase
options = options.symbolize_keys
scope = scope(:find)
merged_includes = merge_includes(scope ? scope[:include] : [], options[:include])
aggregate_alias = column_alias_for(operation, column_name)
if operation == 'count'
if merged_includes.any?
options[:distinct] = true
column_name = options[:select] || [connection.quote_table_name(table_name), primary_key] * '.'
end
if options[:distinct]
use_workaround = !connection.supports_count_distinct?
end
end
sql = "SELECT #{operation}(#{'DISTINCT ' if options[:distinct]}#{column_name}) AS #{aggregate_alias}"
# A (slower) workaround if we're using a backend, like sqlite, that doesn't support COUNT DISTINCT.
sql = "SELECT COUNT(*) AS #{aggregate_alias}" if use_workaround
sql << ", #{options[:group_field]} AS #{options[:group_alias]}" if options[:group]
sql << " FROM (SELECT DISTINCT #{column_name}" if use_workaround
sql << " FROM #{connection.quote_table_name(table_name)} "
if merged_includes.any?
join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(self, merged_includes, options[:joins])
sql << join_dependency.join_associations.collect{|join| join.association_join }.join
end
add_joins!(sql, options, scope)
add_conditions!(sql, options[:conditions], scope)
add_limited_ids_condition!(sql, options, join_dependency) if join_dependency && !using_limitable_reflections?(join_dependency.reflections) && ((scope && scope[:limit]) || options[:limit])
if options[:group]
group_key = connection.adapter_name == 'FrontBase' ? :group_alias : :group_field
sql << " GROUP BY #{options[group_key]} "
end
if options[:group] && options[:having]
# FrontBase requires identifiers in the HAVING clause and chokes on function calls
if connection.adapter_name == 'FrontBase'
options[:having].downcase!
options[:having].gsub!(/#{operation}\s*\(\s*#{column_name}\s*\)/, aggregate_alias)
end
sql << " HAVING #{options[:having]} "
end
sql << " ORDER BY #{options[:order]} " if options[:order]
add_limit!(sql, options, scope)
sql << ')' if use_workaround
sql
end
def execute_simple_calculation(operation, column_name, column, options) #:nodoc:
value = connection.select_value(construct_calculation_sql(operation, column_name, options))
type_cast_calculated_value(value, column, operation)
end
def execute_grouped_calculation(operation, column_name, column, options) #:nodoc:
group_attr = options[:group].to_s
association = reflect_on_association(group_attr.to_sym)
associated = association && association.macro == :belongs_to # only count belongs_to associations
group_field = (associated ? "#{options[:group]}_id" : options[:group]).to_s
group_alias = column_alias_for(group_field)
group_column = column_for group_field
sql = construct_calculation_sql(operation, column_name, options.merge(:group_field => group_field, :group_alias => group_alias))
calculated_data = connection.select_all(sql)
aggregate_alias = column_alias_for(operation, column_name)
if association
key_ids = calculated_data.collect { |row| row[group_alias] }
key_records = association.klass.base_class.find(key_ids)
key_records = key_records.inject({}) { |hsh, r| hsh.merge(r.id => r) }
end
calculated_data.inject(ActiveSupport::OrderedHash.new) do |all, row|
key = type_cast_calculated_value(row[group_alias], group_column)
key = key_records[key] if associated
value = row[aggregate_alias]
all[key] = type_cast_calculated_value(value, column, operation)
all
end
end
private
def validate_calculation_options(operation, options = {})
options.assert_valid_keys(CALCULATIONS_OPTIONS)
end
# Converts a given key to the value that the database adapter returns as
# a usable column name.
# users.id #=> users_id
# sum(id) #=> sum_id
# count(distinct users.id) #=> count_distinct_users_id
# count(*) #=> count_all
def column_alias_for(*keys)
connection.table_alias_for(keys.join(' ').downcase.gsub(/\*/, 'all').gsub(/\W+/, ' ').strip.gsub(/ +/, '_'))
end
def column_for(field)
field_name = field.to_s.split('.').last
columns.detect { |c| c.name.to_s == field_name }
end
def type_cast_calculated_value(value, column, operation = nil)
operation = operation.to_s.downcase
case operation
when 'count' then value.to_i
when 'avg' then value && value.to_f
else column ? column.type_cast(value) : value
end
end
end
end
end
|
