require 'active_support/core_ext/object/blank'
require 'active_support/core_ext/object/try'
module ActiveRecord
module Calculations
# 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")
#
# # because of the named association, it finds the DISTINCT count using LEFT OUTER JOIN.
# Person.count(:conditions => "age > 26 AND job.salary > 60000", :include => :job)
#
# # finds the number of rows matching the conditions and joins.
# Person.count(:conditions => "age > 26 AND job.salary > 60000",
# :joins => "LEFT JOIN jobs on jobs.person_id = person.id")
#
# 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(column_name = nil, options = {})
column_name, options = nil, column_name if column_name.is_a?(Hash)
calculate(:count, column_name, options)
end
# Calculates the average value on a given column. Returns +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'
#
# # Selects the minimum age for any family without any minors
# Person.minimum(:age, :having => 'min(age) > 17', :group => :last_name)
#
# Person.sum("2 * age")
def calculate(operation, column_name, options = {})
if options.except(:distinct).present?
apply_finder_options(options.except(:distinct)).calculate(operation, column_name, :distinct => options[:distinct])
else
if eager_loading? || (includes_values.present? && references_eager_loaded_tables?)
construct_relation_for_association_calculations.calculate(operation, column_name, options)
else
perform_calculation(operation, column_name, options)
end
end
rescue ThrowResult
0
end
private
def perform_calculation(operation, column_name, options = {})
operation = operation.to_s.downcase
distinct = options[:distinct]
if operation == "count"
column_name ||= (select_for_count || :all)
unless arel.ast.grep(Arel::Nodes::OuterJoin).empty?
distinct = true
end
column_name = primary_key if column_name == :all && distinct
distinct = nil if column_name =~ /\s*DISTINCT\s+/i
end
if @group_values.any?
execute_grouped_calculation(operation, column_name, distinct)
else
execute_simple_calculation(operation, column_name, distinct)
end
end
def aggregate_column(column_name)
if @klass.column_names.include?(column_name.to_s)
Arel::Attribute.new(@klass.unscoped.table, column_name)
else
Arel.sql(column_name == :all ? "*" : column_name.to_s)
end
end
def operation_over_aggregate_column(column, operation, distinct)
operation == 'count' ? column.count(distinct) : column.send(operation)
end
def execute_simple_calculation(operation, column_name, distinct) #:nodoc:
# Postgresql doesn't like ORDER BY when there are no GROUP BY
relation = reorder(nil)
if operation == "count" && (relation.limit_value || relation.offset_value)
# Shortcut when limit is zero.
return 0 if relation.limit_value == 0
query_builder = build_count_subquery(relation, column_name, distinct)
else
column = aggregate_column(column_name)
select_value = operation_over_aggregate_column(column, operation, distinct)
relation.select_values = [select_value]
query_builder = relation.arel
end
type_cast_calculated_value(@klass.connection.select_value(query_builder.to_sql), column_for(column_name), operation)
end
def execute_grouped_calculation(operation, column_name, distinct) #:nodoc:
group_attr = @group_values
association = @klass.reflect_on_association(group_attr.first.to_sym)
associated = group_attr.size == 1 && association && association.macro == :belongs_to # only count belongs_to associations
group_fields = Array(associated ? association.foreign_key : group_attr)
group_aliases = group_fields.map { |field| column_alias_for(field) }
group_columns = group_aliases.zip(group_fields).map { |aliaz,field|
[aliaz, column_for(field)]
}
group = @klass.connection.adapter_name == 'FrontBase' ? group_aliases : group_fields
if operation == 'count' && column_name == :all
aggregate_alias = 'count_all'
else
aggregate_alias = column_alias_for(operation, column_name)
end
select_values = [
operation_over_aggregate_column(
aggregate_column(column_name),
operation,
distinct).as(aggregate_alias)
]
select_values.concat group_fields.zip(group_aliases).map { |field,aliaz|
"#{field} AS #{aliaz}"
}
relation = except(:group).group(group.join(','))
relation.select_values = select_values
calculated_data = @klass.connection.select_all(relation.to_sql)
if association
key_ids = calculated_data.collect { |row| row[group_aliases.first] }
key_records = association.klass.base_class.find(key_ids)
key_records = Hash[key_records.map { |r| [r.id, r] }]
end
ActiveSupport::OrderedHash[calculated_data.map do |row|
key = group_columns.map { |aliaz, column|
type_cast_calculated_value(row[aliaz], column)
}
key = key.first if key.size == 1
key = key_records[key] if associated
[key, type_cast_calculated_value(row[aggregate_alias], column_for(column_name), operation)]
end]
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!(/ +/, '_')
@klass.connection.table_alias_for(table_name)
end
def column_for(field)
field_name = field.to_s.split('.').last
@klass.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.respond_to?(:to_d) ? value.to_d : value
else type_cast_using_column(value, column)
end
end
def type_cast_using_column(value, column)
column ? column.type_cast(value) : value
end
def select_for_count
if @select_values.present?
select = @select_values.join(", ")
select if select !~ /(,|\*)/
end
end
def build_count_subquery(relation, column_name, distinct)
column_alias = Arel.sql('count_column')
subquery_alias = Arel.sql('subquery_for_count')
aliased_column = aggregate_column(column_name == :all ? 1 : column_name).as(column_alias)
relation.select_values = [aliased_column]
subquery = relation.arel.as(subquery_alias)
sm = Arel::SelectManager.new relation.engine
select_value = operation_over_aggregate_column(column_alias, 'count', distinct)
sm.project(select_value).from(subquery)
end
end
end
