1. Using the Migrate Module for Fewer Headaches when Relaunching a Site
John Fiala
Developer

2. What it's For You've got an existing website Wordpress Joomla
Custom DB-based Website
And you want to move to Drupal
But you've got users, items, or terms you want to migrate to the new site

3. Sources SQL – Any sort Drupal can read MySQL, Postgres, MS SQL, Oracle
JSON
CSV
XML – Although if you're reading in from someone else's site, Feeds may be what you need

4. Destinations Entity Comment File Node Term User
Table – if defined in the schema
TableCopy – Just copy data from Table A to Table A'

5. How does it work?
Well, you're going to need to do some Object Oriented programming

6. What Gets Migrated? Source: Destination: Users Users
Blog posts, Events, other items
Tags
Comments
Profiles
Destination:
Users
Nodes
Taxonomy Terms
Comments
Other Entities

7. Keep Track of Dependencies
Nodes depend on Users
Nodes depend on Terms
Comments depend on Nodes and Users
Entities depend on Users too
If you've got any Tables you're copying over, chances are something depends on that.

8. Example: Beer!
CC Attribution 2.0 – Jason Dean

9. Example Beer Tables beer_topic beer_account beer_topic_node beer_node
beer_comment

10. beer_topic & beer_topic_node
Look at the Database!

11. Beer Topic Summary: style is the key to beer_topic
style should be mapped to term name
details should be mapped to term description
style_parent should be mapped to the term parent
hoppiness and region may or may not be mapped – there's no obvious destination
Fields?
Part of the description?
Ask the client!

12. Code Time!

13. Getting Fancier
What if we wanted to make a term name include the region and hoppiness fields?
Option 1: Change the SQL to prepare the data.
$query = db_select('migrate_example_beer_topic', 'met')
->fields('met', array('style', 'style_parent', 'region', 'hoppiness'));
$query->addExpression("CONCAT(details, ' region:', region, ' hoppiness:', hoppiness)", 'details');
$query->orderBy('style_parent', 'ASC');

14. Getting Fancier, pt 2
Or, we could let migrate move the data over, and then make changes to the data before it was saved.
We do this by implementing a method called
prepare(stdClass $entity, stdClass $row)

15. Field Mappings AddFieldMapping($destination, $source)
Just maps data from $source to $destination
addSimpleMappings(array($fieldnames))
If you've got fields which are the same name in both source and destination, this maps them quickly

16. Field Mapping Modifiers
defaultValue($value)
Applies $value as the value if the source is empty or if you don't give a source
dedupe($drupal_table, $drupal_column)
Enforces uniqueness on a non-unique source
issueGroup, issuePriority, issueNumber
description($desc)

17. More Field Mapping Modifiers
sourceMigration($migration)
Tells the field mapping to look up the new value for the field in a previous migration
separator($string)
Explodes a string to provide a multi-value result
Arguments()
Some fields are more complex than just one value