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rails--rails/activerecord/lib/active_record/querying.rb
Ryuta Kamizono 7219eb2cd2 Support relation.and for intersection as Set theory
As described at #39328, `relation.merge` behaves inspired as Hash-like
merge for where clause. In other words, currently there is no official
way to intersect the result by both relation conditions (i.e. there is
no official way to maintain both relation conditions).

To resolve that issue, I'd like to support a way to intersect relations
as `relation.and`.

```ruby
david_and_mary = Author.where(id: [david, mary])
mary_and_bob   = Author.where(id: [mary, bob]) # => [bob]

david_and_mary.merge(mary_and_bob) # => [mary, bob]

david_and_mary.and(mary_and_bob) # => [mary]
david_and_mary.or(mary_and_bob)  # => [david, mary, bob]
```

Fixes #39232.
2020-06-07 11:25:51 +09:00

87 lines
4.4 KiB
Ruby

# frozen_string_literal: true
module ActiveRecord
module Querying
QUERYING_METHODS = [
:find, :find_by, :find_by!, :take, :take!, :first, :first!, :last, :last!,
:second, :second!, :third, :third!, :fourth, :fourth!, :fifth, :fifth!,
:forty_two, :forty_two!, :third_to_last, :third_to_last!, :second_to_last, :second_to_last!,
:exists?, :any?, :many?, :none?, :one?,
:first_or_create, :first_or_create!, :first_or_initialize,
:find_or_create_by, :find_or_create_by!, :find_or_initialize_by,
:create_or_find_by, :create_or_find_by!,
:destroy_all, :delete_all, :update_all, :touch_all, :destroy_by, :delete_by,
:find_each, :find_in_batches, :in_batches,
:select, :reselect, :order, :reorder, :group, :limit, :offset, :joins, :left_joins, :left_outer_joins,
:where, :rewhere, :preload, :extract_associated, :eager_load, :includes, :from, :lock, :readonly,
:and, :or, :annotate, :optimizer_hints, :extending,
:having, :create_with, :distinct, :references, :none, :unscope, :merge, :except, :only,
:count, :average, :minimum, :maximum, :sum, :calculate,
:pluck, :pick, :ids, :strict_loading
].freeze # :nodoc:
delegate(*QUERYING_METHODS, to: :all)
# Executes a custom SQL query against your database and returns all the results. The results will
# be returned as an array, with the requested columns encapsulated as attributes of the model you call
# this method from. For example, if you call <tt>Product.find_by_sql</tt>, then the results will be returned in
# a +Product+ object with the attributes you specified in the SQL query.
#
# If you call a complicated SQL query which spans multiple tables, the columns specified by the
# SELECT will be attributes of the model, whether or not they are columns of the corresponding
# table.
#
# The +sql+ parameter is a full SQL query as a string. It will be called as is; there will be
# no database agnostic conversions performed. This should be a last resort because using
# database-specific terms will lock you into using that particular database engine, or require you to
# change your call if you switch engines.
#
# # A simple SQL query spanning multiple tables
# Post.find_by_sql "SELECT p.title, c.author FROM posts p, comments c WHERE p.id = c.post_id"
# # => [#<Post:0x36bff9c @attributes={"title"=>"Ruby Meetup", "author"=>"Quentin"}>, ...]
#
# You can use the same string replacement techniques as you can with <tt>ActiveRecord::QueryMethods#where</tt>:
#
# Post.find_by_sql ["SELECT title FROM posts WHERE author = ? AND created > ?", author_id, start_date]
# Post.find_by_sql ["SELECT body FROM comments WHERE author = :user_id OR approved_by = :user_id", { :user_id => user_id }]
def find_by_sql(sql, binds = [], preparable: nil, &block)
result_set = connection.select_all(sanitize_sql(sql), "#{name} Load", binds, preparable: preparable)
column_types = result_set.column_types
unless column_types.empty?
column_types = column_types.reject { |k, _| attribute_types.key?(k) }
end
message_bus = ActiveSupport::Notifications.instrumenter
payload = {
record_count: result_set.length,
class_name: name
}
message_bus.instrument("instantiation.active_record", payload) do
if result_set.includes_column?(inheritance_column)
result_set.map { |record| instantiate(record, column_types, &block) }
else
# Instantiate a homogeneous set
result_set.map { |record| instantiate_instance_of(self, record, column_types, &block) }
end
end
end
# Returns the result of an SQL statement that should only include a COUNT(*) in the SELECT part.
# The use of this method should be restricted to complicated SQL queries that can't be executed
# using the ActiveRecord::Calculations class methods. Look into those before using this method,
# as it could lock you into a specific database engine or require a code change to switch
# database engines.
#
# Product.count_by_sql "SELECT COUNT(*) FROM sales s, customers c WHERE s.customer_id = c.id"
# # => 12
#
# ==== Parameters
#
# * +sql+ - An SQL statement which should return a count query from the database, see the example above.
def count_by_sql(sql)
connection.select_value(sanitize_sql(sql), "#{name} Count").to_i
end
end
end