Slightly optimize the block upgrade path

I changed 7003 to start with:

function block_update_7003() {
  if(db_index_exists('block', 'list'))
    {
    db_drop_index('block', 'list');
    }

It passed the first error then hit the following message because, with unicode support, all those fields are over 1150 bytes total.
Failed: SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max key length is 1000 bytes

MySQL can combine multiple indexes to find data so I tried again with the following test split of the index. The block updates worked.

  ), array(
    'indexes' => array(
      'theme' => array('theme'),
      'list' => array('status', 'region', 'weight', 'module'),
    ),

I checked a few sites and the D6 sites have the new format but the D5->D6 converted sites have the old format. I checked schema_version for block and they all show zero. Ah, the update is under system, not block. Ok, system is up to 6053. 6043 ran because other tables changed. I suspect having the field change and index add in the same step resulted in the index add occurring before the field changed and the update failed because of the 1000 byte limit. If the block change had been made into two steps, it would have worked.

I made an ugly change to get around the problem:

function block_update_7003() {
  if(db_index_exists('block', 'list'))
    {
    db_drop_index('block', 'list');
    }
  else
    {
    db_change_field('block', 'theme', 'theme', array(
      'type' => 'varchar',
      'length' => 64,
      'not null' => TRUE,
      'default' => ''
      ));
    db_add_unique_key('block', 'tmd', array('theme', 'module', 'delta'));
    }
  db_change_field('block', 'weight', 'weight', array(
    'type' => 'int',
    'not null' => TRUE,
    'default' => 0,
    'description' => 'Block weight within region.',
  ), array(
    'indexes' => array(
      'list' => array('theme', 'status', 'region', 'weight', 'module'),
    ),
  ));
}

Now I get:
Update #7003 * Failed: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'bluemarine-block-1' for key 'tmd'

There are 133 duplicate rows. The only thing I can think of at this stage is to manually clean up my D5->D6 site and go back to testing the D7 conversion with the clean database.

@ctmattice1 I do use a test site. I run the backup module to produce a daily SQL file and back the SQL file up to other computers including my desktop. I then import the SQL into a test site along side tux paint and pictures of insects. Quicker than waiting for an upload to a server plus my neighbour's 4 year old helps me edit the code. When you have to indent with spaces instead of tabs, it is useful to have an assistant who is happy to bash on the spacebar with a lego brick.

My source site is now changed the way 6043 was supposed to change it. My SQL backups no longer create this issue. There is one filter problem to fix then the site should convert.