Class: DirectoryDiff::Transformer::TempTable

Inherits:
Object
  • Object
show all
Defined in:
lib/directory_diff/transformer/temp_table.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(current_directory) ⇒ TempTable

Returns a new instance of TempTable.



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# File 'lib/directory_diff/transformer/temp_table.rb', line 14

def initialize(current_directory)
  @current_directory = current_directory
  @operations = []
end

Instance Attribute Details

#current_directory ⇒ Object (readonly)

Returns the value of attribute current_directory.



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# File 'lib/directory_diff/transformer/temp_table.rb', line 8

def current_directory
  @current_directory
end

#operations ⇒ Object (readonly)

Returns the value of attribute operations.



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# File 'lib/directory_diff/transformer/temp_table.rb', line 8

def operations
  @operations
end

Instance Method Details

#into(new_directory, options = {}) ⇒ Object

Parameters:

  • new_directory —

    a table containing only the new records to compare against, most likely a temp table.



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# File 'lib/directory_diff/transformer/temp_table.rb', line 21

def into(new_directory, options = {})
  current_directory_temp_table do |temp_current_directory|
    new_directory_temp_table(new_directory) do |deduped_csv|
      # Get Arel tables for referencing fields, table names
      employees = temp_current_directory.table
      csv = deduped_csv.table

      # Reusable Arel predicates
      csv_employee_join = csv[:email].eq(employees[:email])
      attributes_unchanged = employees[:name].eq(csv[:name])
                              .and(
                                employees[:phone_number].eq(csv[:phone_number])
                                  .or(csv[:phone_number].eq(""))
                                  # ☝🏽 Comparing to an empty string because we cast
                                  # phone number to an empty string. The reason is
                                  # comparing NULL = NULL is always false in SQL
                              )
                              .and(
                                employees[:assistants].eq(csv[:assistants])
                                  .or(csv[:assistants].eq("{}"))
                              )

      # Creates joins between the temp table and the csv table and
      # vice versa
      # Cribbed from https://gist.github.com/mildmojo/3724189
      csv_to_employees = csv.join(employees, Arel::Nodes::OuterJoin)
                          .on(csv_employee_join)
                          .join_sources
      employees_to_csv = employees.join(csv, Arel::Nodes::OuterJoin)
                          .on(csv_employee_join)
                          .join_sources

      # Representation of the joined csv-employees, with csv on the left
      csv_records = deduped_csv.joins(csv_to_employees).order('row_number asc')
      # Representation of the joined employees-csv, with employees on the
      # left
      employee_records = temp_current_directory.joins(employees_to_csv)

      connection.execute(SQL.cleanup_sql(csv.name))

      csv_fields = %I[name email phone_number assistants extra].map { |c| csv[c] }
      emp_fields = %I[name email phone_number assistants].map { |c| employees[c] }

      # new records are records in the new directory that don't exist in
      # the current directory
      new_records = csv_records
                      .select("'insert'::varchar operation, row_number")
                      .select(csv_fields)
                      .where({ employees.name => { email: nil } })
      # deleted records are records in the current directory that don't
      # exist in the new directory
      deleted_records = employee_records
                          .select("'delete'::varchar operation, row_number")
                          .select(emp_fields)
                          .select("null extra")
                          .where({ csv.name => { email: nil } })
      # changed records are records that have difference in name, phone
      # number and/or assistants
      changed_records = csv_records
                          .select("'update'::varchar operation, row_number")
                          .select(csv_fields)
                          .where.not(attributes_unchanged)
      # unchanged records are records that are exactly the same in both
      # directories (without considering the extra field)
      unchanged_records = csv_records
                            .select("'noop'::varchar operation, row_number")
                            .select(csv_fields)
                            .where(attributes_unchanged)

      # create temp table for holding operations
      temp_table(new_records.to_sql) do |operations|
        insert_into_operations(operations, deleted_records.to_sql)
        insert_into_operations(operations, changed_records.to_sql)
        if options[:skip_noop] != true
          insert_into_operations(operations, unchanged_records.to_sql)
        end

        operations.order(:row_number).each do |operation|
          add_operation(operation)
        end
      end
    end
  end

  prioritize_assistants(operations)
end