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module ActiveRecord
module Calculations #:nodoc:
extend ActiveSupport::DependencyModule
CALCULATIONS_OPTIONS = [:conditions, :joins, :order, :select, :group, :having, :distinct, :limit, :offset, :include, :from]
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 to ActiveRecord::Base.
# * <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 <tt>:include</tt> 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 <tt>:readonly => false</tt> 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) ...
# * <tt>:from</tt> - By default, this is the table name of the class, but can be changed to an alternate table name (or even the name
# of a database view).
#
# 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: <tt>Person.count(:all)</tt> will not work because it will use <tt>:all</tt> 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, or +nil+ if there's no row. See +calculate+ for examples with
# options.
#
# Person.average('age') # => 35.8
def average(column_name, options = {})
calculate(:average, column_name, options)
end
# Calculates the minimum value on a given column. The value is returned
# with the same data type of the column, or +nil+ if there's no row. See
# +calculate+ for examples with options.
#
# Person.minimum('age') # => 7
def minimum(column_name, options = {})
calculate(:minimum, column_name, options)
end
# Calculates the maximum value on a given column. The value is returned
# with the same data type of the column, or +nil+ if there's no row. See
# +calculate+ for examples with options.
#
# Person.maximum('age') # => 93
def maximum(column_name, options = {})
calculate(:maximum, 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, 0 if there's no row. See
# +calculate+ for examples with options.
#
# Person.sum('age') # => 4562
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 <tt>:conditions</tt>, <tt>:order</tt>, <tt>:group</tt>, <tt>:having</tt>, and <tt>:joins</tt> 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 <tt>:group</tt> 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 to ActiveRecord::Base.
# * <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
# Person.sum("2 * age")
def calculate(operation, column_name, options = {})
validate_calculation_options(operation, options)
operation = operation.to_s.downcase
scope = scope(:find)
merged_includes = merge_includes(scope ? scope[:include] : [], options[:include])
joins = construct_join(options[:joins], scope)
if merged_includes.any?
join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(self, merged_includes, joins)
joins << join_dependency.join_associations.collect{|join| join.association_join }.join
end
if operation == "count"
if merged_includes.any?
distinct = true
column_name = options[:select] || primary_key
end
distinct = nil if column_name.to_s =~ /\s*DISTINCT\s+/i
distinct ||= options[:distinct]
else
distinct = nil
end
catch :invalid_query do
conditions = construct_conditions(options[:conditions], scope)
conditions << construct_limited_ids_condition(conditions, options, join_dependency) if join_dependency && !using_limitable_reflections?(join_dependency.reflections) && ((scope && scope[:limit]) || options[:limit])
if options[:group]
return execute_grouped_calculation(operation, column_name, options.merge(:conditions => conditions, :joins => joins, :distinct => distinct))
else
return execute_simple_calculation(operation, column_name, options.merge(:conditions => conditions, :joins => joins, :distinct => distinct))
end
end
0
end
def execute_simple_calculation(operation, column_name, options) #:nodoc:
column = if column_names.include?(column_name.to_s)
Arel::Attribute.new(arel_table(options[:from] || table_name),
options[:select] || column_name)
else
Arel::SqlLiteral.new(options[:select] ||
(column_name == :all ? "*" : column_name.to_s))
end
value = construct_calculation_arel(options.merge(
:select => operation == 'count' ? column.count(options[:distinct]) : column.send(operation)
))
type_cast_calculated_value(connection.select_value(value.to_sql), column_for(column_name), operation)
end
def execute_grouped_calculation(operation, column_name, 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 ? association.primary_key_name : group_attr
group_alias = column_alias_for(group_field)
group_column = column_for group_field
options[:group] = connection.adapter_name == 'FrontBase' ? group_alias : group_field
aggregate_alias = column_alias_for(operation, column_name)
options[:select] = (operation == 'count' && column_name == :all) ?
"COUNT(*) AS count_all" :
Arel::Attribute.new(arel_table, column_name).send(operation).as(aggregate_alias).to_sql
options[:select] << ", #{group_field} AS #{group_alias}"
calculated_data = connection.select_all(construct_calculation_arel(options).to_sql)
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_for(column_name), operation)
all
end
end
protected
def construct_calculation_arel(options)
scope = scope(:find)
arel_table(options[:from] || table_name).
join(options[:joins]).
where(options[:conditions]).
project(options[:select]).
group(construct_group(options[:group], options[:having], scope)).
order(options[:order].to_s).
take(construct_limit(options, scope)).
skip(construct_offset(options, scope)
)
end
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={})
# selects specified by scopes
case args.size
when 0
column_name = scope(:find)[:select] if scope(:find)
when 1
if args[0].is_a?(Hash)
column_name = scope(:find)[:select] if scope(:find)
options = args[0]
else
column_name = args[0]
end
when 2
column_name, options = args
else
raise ArgumentError, "Unexpected parameters passed to count(): #{args.inspect}"
end
[column_name || :all, options]
end
private
def validate_calculation_options(operation, options = {})
options.assert_valid_keys(CALCULATIONS_OPTIONS)
end
# Converts the given keys to the value that the database adapter returns as
# a usable column name:
#
# column_alias_for("users.id") # => "users_id"
# column_alias_for("sum(id)") # => "sum_id"
# column_alias_for("count(distinct users.id)") # => "count_distinct_users_id"
# column_alias_for("count(*)") # => "count_all"
# column_alias_for("count", "id") # => "count_id"
def column_alias_for(*keys)
table_name = keys.join(' ')
table_name.downcase!
table_name.gsub!(/\*/, 'all')
table_name.gsub!(/\W+/, ' ')
table_name.strip!
table_name.gsub!(/ +/, '_')
connection.table_alias_for(table_name)
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)
case operation
when 'count' then value.to_i
when 'sum' then type_cast_using_column(value || '0', column)
when 'average' then value && (value.is_a?(Fixnum) ? value.to_f : value).to_d
else type_cast_using_column(value, column)
end
end
def type_cast_using_column(value, column)
column ? column.type_cast(value) : value
end
end
end
end
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