Duplicate taxonomy terms inserted by freeform tagging. Fix included.

The function taxonomy_save_term currently allows freeform tagging to create duplicate term names in the database. To prevent duplicate terms in the same vocabulary from being inserted from freetagging, do the following:

First, add a $vid paramter to function taxonomy_get_term_by_name for easier calling.

replace:

function taxonomy_get_term_by_name($name) {
  $db_result = db_query(db_rewrite_sql("SELECT t.tid, t.* FROM {term_data} t WHERE LOWER('%s') LIKE LOWER(t.name)", 't', 'tid'), trim($name));

with:

function taxonomy_get_term_by_name($name, $vid = 0) {
  if ($vid) {
    $db_result = db_query(db_rewrite_sql("SELECT t.tid, t.* FROM {term_data} t WHERE LOWER('%s') LIKE LOWER(t.name) AND t.vid = %d", 't', 'tid'), trim($name), $vid);
  }
  else {
    $db_result = db_query(db_rewrite_sql("SELECT t.tid, t.* FROM {term_data} t WHERE LOWER('%s') LIKE LOWER(t.name)", 't', 'tid'), trim($name));
  }

Then edit taxonomy.module and replace:

function taxonomy_save_term(&$form_values) {
  if ($form_values['tid'] && $form_values['name']) {
    db_query("UPDATE {term_data} SET name = '%s', description = '%s', weight = %d WHERE tid = %d", $form_values['name'], $form_values['description'], $form_values['weight'], $form_values['tid']);
    $hook = 'update';
    $status = SAVED_UPDATED;
  }
  else if ($form_values['tid']) {
    return taxonomy_del_term($form_values['tid']);
  }
  else {
    $form_values['tid'] = db_next_id('{term_data}_tid');
    db_query("INSERT INTO {term_data} (tid, name, description, vid, weight) VALUES (%d, '%s', '%s', %d, %d)", $form_values['tid'], $form_values['name'], $form_values['description'], $form_values['vid'], $form_values['weight']);
    $hook = 'insert';
    $status = SAVED_NEW;
  }

with:

  function taxonomy_save_term(&$form_values) {
    if ($form_values['tid'] && $form_values['name']) {
      db_query("UPDATE {term_data} SET name = '%s', description = '%s', weight = %d WHERE tid = %d", $form_values['name'], $form_values['description'], $form_values['weight'], $form_values['tid']);
      $hook = 'update';
      $status = SAVED_UPDATED;
    }
    else if ($form_values['tid']) {
      return taxonomy_del_term($form_values['tid']);
    }
    else {
      // Make sure it doesn't exist first
      $termexists = taxonomy_get_term_by_name($form_values['name'], $form_values['vid']);
      if (!empty($termexists)) { 
        $form_values['tid'] = $termexists->tid;
        db_query("UPDATE {term_data} SET name = '%s', description = '%s', weight = %d WHERE tid = %d", $form_values['name'], $form_values['description'], $form_values['weight'], $form_values['tid']);
        $hook = 'update';
        $status = SAVED_UPDATED;
      }
      else {
        $form_values['tid'] = db_next_id('{term_data}_tid');
        db_query("INSERT INTO {term_data} (tid, name, description, vid, weight) VALUES (%d, '%s', '%s', %d, %d)", $form_values['tid'], $form_values['name'], $form_values['description'], $form_values['vid'], $form_values['weight']);
        $hook = 'insert';
        $status = SAVED_NEW;
      }
  }

I'll figure out how to create patches sometime soon.