Column not found: 1054 Unknown column 't.tid' during upgrade from 6.x-1 to 7.x-1

After that, I get other errors:

The update process was aborted prematurely while running update #7000 in taxonomy_image.module.

An AJAX HTTP error occurred. HTTP Result Code: 200 Debugging information follows. Path: .../update.php?op=selection&token=...-uHA&id=219&op=do StatusText: OK ResponseText: Fatal error: Cannot use object of type DatabaseConnection_mysql as array in ...\sites\all\modules\taxonomy_image\taxonomy_image.install on line 43

Strict warning: Only variables should be passed by reference in update_results_page() (line 171 of ...\update.php).

I've retried a full D6 --> D7 upgrade and I get a different message now:

Update #7000
Failed: FieldException: Attempt to create an instance of field taxonomy_image without a bundle. in field_create_instance() (line 464 of ...\modules\field\field.crud.inc).

$term->vocabulary_machinename

is the cause of missing bundle and it should be corrected into the following:

$term->vocabulary_machine_name

We're getting closer, step by step, but there is another problem: after applying fixes and upgrading, the taxonomy terms have empty images and I get an error if I try to delete/replace them:

File ... could not be deleted because it is not a valid URI. This may be caused by improper use of file_delete() or a missing stream wrapper.

I think that a better manage of URI it is needed during conversion, but I'm not an expert... Maybe the Ubercart catalog module would be a good example, since it does similar upgrade --> see uc_catalog.install

I've retried, now there is another problem:

Update #7000
Failed: PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'public://_A_FILE_NAME_.png' for key 'uri': INSERT INTO {file_managed} (uri, filesize, status, timestamp) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3); Array ( [:db_insert_placeholder_0] => public://_A_FILE_NAME_.png [:db_insert_placeholder_1] => 303411 [:db_insert_placeholder_2] => 1 [:db_insert_placeholder_3] => 1336889803 ) in drupal_write_record() (line 7013 of ...\includes\common.inc).

Maybe this is due to the fact that some taxonomy term on my site uses the same image filename as of certain products (nodes).
For example:
- node A has the image filename imageA.png stored in ...\sites\default\files
- taxonomy term A has the same image filename imageA.png stored in ...\sites\default\files\category_pictures
This is similar to #1176186: D6 -> D7 upgrade: Duplicate files cause Integrity constraint violation: 1062 Duplicate entry 'xx' for key 'PRIMARY' so I think I can resolve it by forcing a unique filename for every taxonomy term...

I've retried again, after deleting all image name duplications.
Now there is another kind of problem:

Warning: filesize() [function.filesize]: stat failed for public://_A_FILE_NAME_.png in file_save() (line 570 of ...\includes\file.inc).

FYI I was able to merge logic from uc_catalog.install into the following taxonomy_image.install and it worked !

/**
 * @file
 * Update functions for the taxonomy_image module.
 */

/**
 * Upgrades field data from the Drupal 6 version.
 */
function taxonomy_image_update_7000(&$context) {
  if (!db_table_exists('term_image')) {
    return;
  }

  $query = db_select('term_image', 't')
    ->fields('t', array('tid', 'path'));

  // Initiliaze by creating the field and counting the entries.
  if (!isset($sandbox['progress'])) {
    $sandbox['progress'] = 0;
    $sandbox['max'] = $query->countQuery()->execute()->fetchField();
    $sandbox['last_tid'] = -1;

    if (!field_info_field('taxonomy_image')) {
      field_create_field(array(
        'field_name' => 'taxonomy_image',
        'type' => 'image',
        'cardinality' => 1,
        'translatable' => TRUE,
        'entity_types' => array('taxonomy_term'),
      ));
    }
  }

  // Select ten rows at a time.
  $result = $query
    ->orderBy('tid', 'ASC')
//    ->range(0, 10)
    ->condition('tid', $sandbox['last_tid'], '>')
    ->execute();

  // Upgrade each row.
  while($row = $result->fetchAssoc()) {
    $rows_exist = TRUE;

    // Load the term.
    $term = taxonomy_term_load($row['tid']);
    if (!$term) {
      continue;
    }
    $bundle = $term->vocabulary_machine_name;

    // Ensure the taxonomy_image field is instanciated.
    if (!field_info_instance('taxonomy_term', 'taxonomy_image', $bundle)) {
      field_create_instance(array(
        'field_name' => 'taxonomy_image',
        'entity_type' => 'taxonomy_term',
        'label' => t('Image'),
        'bundle' => $bundle,
        'description' => t('The image of this term.'),
        'required' => FALSE,
        'widget' => array(
          'type' => 'image_image',
        ),
      ));
    }

    $files = db_query_range('SELECT tid, f.fid, uid, filename, filepath AS uri, filemime, filesize, status, timestamp FROM {term_image} ti inner join {files} f on f.filename = ti.path where tid = :current', 0, 500, array(':current' => $row['tid']), array('fetch' => PDO::FETCH_ASSOC));
    $basename = variable_get('file_directory_path', conf_path() . '/files');
    $scheme = variable_get('file_default_scheme', 'public') . '://';

    foreach ($files as $file) {
      // Get term id for the image.
      $tid = $file['tid'];
      // Don't break the insert query with extra data.
      unset($file['tid']);

      $file['uri'] = $scheme . str_replace($basename, '', $file['uri']);
      $file['uri'] = file_stream_wrapper_uri_normalize($file['uri']);
      db_merge('file_managed')
        ->key(array('fid' => $file['fid']))
        ->fields(array(
          'uid' => $file['uid'],
          'filename' => $file['filename'],
          'uri' => $file['uri'],
          'filemime' => $file['filemime'],
          'filesize' => $file['filesize'],
          'status' => $file['status'],
          'timestamp' => $file['timestamp'],
        ))
        ->execute();

      // Add the usage entry for the file.
      file_usage_add((object) $file, 'file', 'taxonomy_term', $tid);

      $term = (object) array(
        'tid' => $tid,
        'taxonomy_image' => array(
          LANGUAGE_NONE => array(
            0 => array(
              'fid' => $file['fid'],
            ),
          ),
        ),
      );

      _update_7000_field_sql_storage_write('taxonomy_term', $bundle, $term->tid, NULL, 'taxonomy_image', $term->taxonomy_image);

      $sandbox['message'] = check_plain($file['filename']);
    }

    // Increase counters.
    $sandbox['progress']++;
    $sandbox['last_tid'] = $term->tid;
  }

  // Finalize.
  if (empty($rows_exist)) {
    db_drop_table('term_image');
    return t('Taxonomy image field data has been migrated. Settings must be adjusted manually.');
  }
  else {
    $sandbox['#finished'] = $sandbox['progress'] / $sandbox['max'];
  }
}

See the attached patch. Warning: newbie here !

I tried to keep the range statement, but it caused to process only 10 records. Keep in mind that I'm not an expert in PHP... So, since I have <200 terms, I preferred to work them all together.

I've done another upgrade cycle with patch #19 and all taxonomy images were managed correctly.
Thanks !