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
    @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 85

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