Module: Sequel::Plugins::FromCsv::ClassMethods

Defined in:
lib/sequel/plugins/from_csv.rb

Instance Method Summary collapse

Instance Method Details

#seed_from_csv(csv_path, delete_missing: false, reset_sequence: false) ⇒ Object

Synchronizes a table’s data with a CSV file. Returns self.

The table being synchronized must contain exactly one primary key column, and the CSV file used must contain the primary key column as one of its fields.

Options:

:delete_missing

whether to remove rows from the table that were not found in the CSV file

:reset_sequence

whether to update the primary key’s sequence to reflect the max primary key value

:reset_sequence only works on PostgreSQL tables that auto-increment their primary keys using sequences

Usage:

class Artist < Sequel::Model
  plugin :from_csv
end
Artist.seed_from_csv "seeds/artists.csv", reset_sequence: true



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# File 'lib/sequel/plugins/from_csv.rb', line 29

def seed_from_csv csv_path, delete_missing: false, reset_sequence: false

  # Read the source CSV file
  data = CSV.table csv_path, converters: :date_time

  # Guard against CSV files that have headers but not data (to handle a quirk in Ruby's CSV parser)
  if data.headers.empty?
    raise MissingDataException, "CSV file #{csv_path} did not contain any data rows"
  end

  # Check that all primary key columns are present
  pk = self.primary_key
  if Array === pk
    raise NotYetImplementedException, "Sequel::Plugins::FromCsv does not yet support composite primary keys."
  end

  # Ensure the ID column exists
  unless data.headers.include? pk
    raise MissingFieldException, "CSV file #{csv_path} must contain a column named '#{pk}'"
  end

  self.db.transaction do

    # UPSERT
    data.each do |row|
      row = row.to_h # Convert CSV::Row to Hash
      self.dataset.insert_conflict(target: pk, update: row).insert row
    end

    # DELETE old rows
    if delete_missing
      self.exclude(pk => data.map{|row| row[pk]}).delete
    end

    # Update the table's sequence
    if reset_sequence
      case self.db.database_type
      when :postgres
        self.db.run "          SELECT\n            setval(pg_get_serial_sequence('\#{self.simple_table}', '\#{pk}'), greatest(max(\#{pk}), 1), true)\n          FROM\n            \#{self.simple_table}\n        SQL\n      end\n    end\n\n  end\n\n  # Should return itself\n  self\n\nend\n"