Module: TemporalTables::RelationExtensions

Defined in:
lib/temporal_tables/relation_extensions.rb

Overview

Stores the time from the “at” field into each of the resulting objects so that it can be carried forward in subsequent queries.

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.included(base) ⇒ Object 



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# File 'lib/temporal_tables/relation_extensions.rb', line 5

def self.included(base)
	base.class_eval do
		ActiveRecord::Relation::SINGLE_VALUE_METHODS << :at
	end
end

Instance Method Details

#at(*args) ⇒ Object 



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# File 'lib/temporal_tables/relation_extensions.rb', line 19

def at(*args)
    spawn.at!(*args)
end

#at!(value) ⇒ Object 



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# File 'lib/temporal_tables/relation_extensions.rb', line 23

def at!(value)
	self.at_value = value
	self
end

#at_value ⇒ Object 



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# File 'lib/temporal_tables/relation_extensions.rb', line 11

def at_value
  get_value(:at) || Thread.current[:at_time]
end

#at_value=(value) ⇒ Object 



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# File 'lib/temporal_tables/relation_extensions.rb', line 15

def at_value=(value)
  set_value(:at, value)
end

#exec_queries ⇒ Object 



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# File 'lib/temporal_tables/relation_extensions.rb', line 67

def exec_queries
	# Note that record preloading, like when you specify
	#  MyClass.includes(:associations)
	# happens within this exec_queries call.  That's why we needed to
	# store the at_time in the thread above.
	threadify_at do
		super
	end

	if historical?
		# Store the at value on each record returned
		# TODO: traverse preloaded associations too
		@records.each do |r|
			r.at_value = at_value
		end
	end
	@records
end

#historical? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/temporal_tables/relation_extensions.rb', line 86

def historical?
	table_name =~ /_h$/i && at_value
end

#limited_ids_for(*args) ⇒ Object 



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# File 'lib/temporal_tables/relation_extensions.rb', line 61

def limited_ids_for(*args)
	threadify_at do
		super *args
	end
end

#threadify_at ⇒ Object 



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# File 'lib/temporal_tables/relation_extensions.rb', line 50

def threadify_at
	if at_value && !Thread.current[:at_time]
		Thread.current[:at_time] = at_value
		result = yield
		Thread.current[:at_time] = nil
	else
		result = yield
	end
	result
end

#to_sql(*args) ⇒ Object 



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# File 'lib/temporal_tables/relation_extensions.rb', line 44

def to_sql(*args)
	threadify_at do
		super *args
	end
end

#where_clause ⇒ Object 



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# File 'lib/temporal_tables/relation_extensions.rb', line 28

def where_clause
	s = super

	at_clauses = []
	if historical?
		at_clauses << where_clause_factory.build(
			arel_table[:eff_to].gteq(at_value).and(
				arel_table[:eff_from].lteq(at_value)
			),
			[]
		)
	end

	[s, *at_clauses.compact].sum
end