- Patch #374940 by Dave Reid et al: fixed MergeQuery problem.

includes/database/mysql/query.inc

@@ -143,6 +143,12 @@ public function __toString() {
       }
     }
 
+    // If the merge query has no fields to update, add the first key as an
+    // update field so the query will not fail if a duplicate key is found.
+    if (!$update_fields && !$this->expressionFields) {
+      $update_fields = array_slice($this->keyFields, 0, 1, TRUE);
+    }
+
     $insert_fields = $this->insertFields + $this->keyFields;
 
     $query = "INSERT INTO {" . $this->table . '} (' . implode(', ', array_keys($insert_fields)) . ') VALUES ';

includes/database/query.inc

@@ -676,14 +676,17 @@ public function execute() {
           unset($update_fields[$exclude_field]);
         }
       }
-      $update = $this->connection->update($this->table, $this->queryOptions)->fields($update_fields);
-      foreach ($this->keyFields as $field => $value) {
-        $update->condition($field, $value);
-      }
-      foreach ($this->expressionFields as $field => $expression) {
-        $update->expression($field, $expression['expression'], $expression['arguments']);
+      if ($update_fields || $this->expressionFields) {
+        // Only run the update if there are no fields or expressions to update.
+        $update = $this->connection->update($this->table, $this->queryOptions)->fields($update_fields);
+        foreach ($this->keyFields as $field => $value) {
+          $update->condition($field, $value);
+        }
+        foreach ($this->expressionFields as $field => $expression) {
+          $update->expression($field, $expression['expression'], $expression['arguments']);
+        }
+        $update->execute();
       }
-      $update->execute();
     }
     else {
       // If there is no existing record, run an insert query.

modules/simpletest/tests/database_test.test

@@ -958,6 +958,58 @@ class DatabaseMergeTestCase extends DatabaseTestCase {
     $this->assertEqual($person->job, 'Speaker', t('Job set correctly.'));
   }
 
+  /**
+   * Test that we can merge-insert without any update fields.
+   */
+  function testMergeInsertWithoutUpdate() {
+    $num_records_before = db_query("SELECT COUNT(*) FROM {test_people}")->fetchField();
+
+    db_merge('test_people')
+      ->key(array('job' => 'Presenter'))
+      ->execute();
+
+    $num_records_after = db_query("SELECT COUNT(*) FROM {test_people}")->fetchField();
+    $this->assertEqual($num_records_before + 1, $num_records_after, t('Merge inserted properly.'));
+
+    $person = db_query("SELECT * FROM {test_people} WHERE job = :job", array(':job' => 'Presenter'))->fetch();
+    $this->assertEqual($person->name, '', t('Name set correctly.'));
+    $this->assertEqual($person->age, 0, t('Age set correctly.'));
+    $this->assertEqual($person->job, 'Presenter', t('Job set correctly.'));
+  }
+
+  /**
+   * Confirm that we can merge-update without any update fields.
+   */
+  function testMergeUpdateWithoutUpdate() {
+    $num_records_before = db_query("SELECT COUNT(*) FROM {test_people}")->fetchField();
+
+    db_merge('test_people')
+      ->key(array('job' => 'Speaker'))
+      ->execute();
+
+    $num_records_after = db_query("SELECT COUNT(*) FROM {test_people}")->fetchField();
+    $this->assertEqual($num_records_before, $num_records_after, t('Merge skipped properly.'));
+
+    $person = db_query("SELECT * FROM {test_people} WHERE job = :job", array(':job' => 'Speaker'))->fetch();
+    $this->assertEqual($person->name, 'Meredith', t('Name skipped correctly.'));
+    $this->assertEqual($person->age, 30, t('Age skipped correctly.'));
+    $this->assertEqual($person->job, 'Speaker', t('Job skipped correctly.'));
+
+    db_merge('test_people')
+      ->key(array('job' => 'Speaker'))
+      ->fields(array('age' => 31))
+      ->updateExcept(array('age'))
+      ->execute();
+
+    $num_records_after = db_query("SELECT COUNT(*) FROM {test_people}")->fetchField();
+    $this->assertEqual($num_records_before, $num_records_after, t('Merge skipped properly.'));
+
+    $person = db_query("SELECT * FROM {test_people} WHERE job = :job", array(':job' => 'Speaker'))->fetch();
+    $this->assertEqual($person->name, 'Meredith', t('Name skipped correctly.'));
+    $this->assertEqual($person->age, 30, t('Age skipped correctly.'));
+    $this->assertEqual($person->job, 'Speaker', t('Job skipped correctly.'));
+  }
+
   /**
    * Test that an invalid merge query throws an exception like it is supposed to.
    */