Class: Hayfork::UpdateSql

Inherits:
Object
  • Object
show all
Defined in:
lib/hayfork/update_sql.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(haystack, relation, bindings) ⇒ UpdateSql 



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# File 'lib/hayfork/update_sql.rb', line 8

def initialize(haystack, relation, bindings)
  @haystack = haystack
  @relation = relation
  @bindings = bindings
end

Instance Attribute Details

#bindings ⇒ Object (readonly)

Returns the value of attribute bindings.



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# File 'lib/hayfork/update_sql.rb', line 6

def bindings
  @bindings
end

#haystack ⇒ Object (readonly)

Returns the value of attribute haystack.



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# File 'lib/hayfork/update_sql.rb', line 6

def haystack
  @haystack
end

#relation ⇒ Object (readonly)

Returns the value of attribute relation.



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# File 'lib/hayfork/update_sql.rb', line 6

def relation
  @relation
end

Instance Method Details

#model ⇒ Object 



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# File 'lib/hayfork/update_sql.rb', line 26

def model
  relation.model
end

#to_sql ⇒ Object Also known as: to_s 



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# File 'lib/hayfork/update_sql.rb', line 14

def to_sql
  sql = values_to_check_on_update.map { |field| "OLD.#{field} IS DISTINCT FROM NEW.#{field}" }.join(" OR ")

  <<-SQL
IF #{sql} THEN
  #{delete.to_sql.strip}
  #{insert.to_sql.strip}
END IF;
  SQL
end

#values_to_check_on_update ⇒ Object 



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# File 'lib/hayfork/update_sql.rb', line 30

def values_to_check_on_update
  foreign_keys_by_table_name = {}
  (relation.joins_values + relation.left_outer_joins_values).each do |join_value|
    if join_value.is_a? String
      fail NotImplementedError, "Unhandled literal join: #{join_value.inspect}"
    end

    reflection = reflection_for(join_value)
    table_name = reflection.table_name
    reflection = reflection.through_reflection if reflection.is_a?(ActiveRecord::Reflection::ThroughReflection)

    case reflection
    when ActiveRecord::Reflection::BelongsToReflection
      foreign_keys_by_table_name[table_name] = [ reflection.foreign_key.to_s ]
    when ActiveRecord::Reflection::HasManyReflection
      foreign_keys_by_table_name[table_name] = [] # assume identity keys won't change
    when ActiveRecord::Reflection::HasAndBelongsToManyReflection
      foreign_keys_by_table_name[reflection.join_table] = [] # assume identity keys won't change
      foreign_keys_by_table_name[table_name] = [] # assume identity keys won't change
    else
      fail NotImplementedError, "Unhandled reflection: #{reflection.class} (join_value: #{join_value.inspect})"
    end
  end


  values_being_written = bindings.pluck(:raw_value) + predicate_fields
  values_to_check_on_update = Set.new

  values_being_written.each do |value|
    next if value.is_a?(String) # constant
    if value.relation.name == relation.table_name
      values_to_check_on_update << value.name.to_s
    else
      # The value isn't a field of the current record but of a joined record.
      # That record hasn't changed so we don't care about its value; but we
      # do care whether this record's foreign keys have changed (which would
      # cause it to be associated with a different joined record).
      values_to_check_on_update.merge foreign_keys_by_table_name.fetch(value.relation.name)
    end
  end

  values_to_check_on_update - model.readonly_attributes
end