Class: Migraine::Migration

Inherits:
Map
  • Object
show all
Includes:
Generator
Defined in:
lib/migraine/migration.rb

Overview

This is a special case of a ‘Migraine::Map` as it specifies source and destination databases and provides methods to, for example, run the migration. It also overrides Migraine::Map#set_source_and_destination_from(s_and_d) to accept surce and destination in a more elegant way.

Instance Attribute Summary collapse

Attributes inherited from Map

#destination, #maps, #source

Instance Method Summary collapse

Methods included from Generator

#database_schema_for, #database_schema_for_mysql, #generate

Methods inherited from Map

#initialize, #map

Constructor Details

This class inherits a constructor from Migraine::Map

Instance Attribute Details

#prefix(new_prefix = nil) ⇒ Object

DSL convenience method for skipping the assignment operator when specifying prefix.

Parameters:

  • Prefix (String) —

    to use in generations.



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# File 'lib/migraine/migration.rb', line 55

def prefix
  @prefix
end

Instance Method Details

#run ⇒ Object

Runs the migration using the mappings that have been set up. Walks through the nested Map objects, copying database records from source to destination.



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# File 'lib/migraine/migration.rb', line 15

def run
  connect
  src = @source_connection
  dest = @destination_connection

  log "BEGINNING MIGRATION\n" +
      "-------------------"

  # Iterate through table mappings
  maps.each do |table|
    log "MIGRATING TABLE #{table.source}"

    # Fetch all rows from source table
    rows = src[table.source.to_sym].all
    
    # Iterate through the records and migrate each one
    rows.each do |row|
      new_record = {}

      # Identify the columns we need to grab data from
      table.maps.each do |column|
        new_record.merge!(
          column.destination.to_sym => row[column.source.to_sym]
        )
      end

      # Insert new record to destination table
      log " -> Inserting record into #{table.destination}"
      dest[table.destination.to_sym].insert(new_record)
    end
  end

  log "-------------------\n" +
      "MIGRATION COMPLETED"
end