- Patch #321100 by hswong3i: empty insert statements are better handled now. Comes with tests.

includes/database/mysql/query.inc

@@ -16,6 +16,10 @@ public function execute() {
       throw new PDOException('You may not specify the same field to have a value and a schema-default value.');
     }
 
+    if (count($this->insertFields) + count($this->defaultFields) == 0) {
+      return NULL;
+    }
+
     $last_insert_id = 0;
 
     $max_placeholder = 0;

includes/database/pgsql/query.inc

@@ -22,6 +22,10 @@ public function execute() {
       throw new PDOException('You may not specify the same field to have a value and a schema-default value.');
     }
 
+    if (count($this->insertFields) + count($this->defaultFields) == 0) {
+      return NULL;
+    }
+
     $schema = drupal_get_schema($this->table);
 
     $stmt = $this->connection->prepareQuery((string)$this);

includes/database/query.inc

@@ -382,7 +382,9 @@ public function delay($delay = TRUE) {
    *   was given multiple sets of values to insert, the return value is
    *   undefined.  If the query is flagged "delayed", then the insert ID
    *   won't be created until later when the query actually runs so the
-   *   return value is also undefined.
+   *   return value is also undefined. If no fields are specified, this
+   *   method will do nothing and return NULL. That makes it safe to use
+   *   in multi-insert loops.
    */
   public function execute() {
 
@@ -394,6 +396,10 @@ public function execute() {
       throw new PDOException('You may not specify the same field to have a value and a schema-default value.');
     }
 
+    if (count($this->insertFields) + count($this->defaultFields) == 0) {
+      return NULL;
+    }
+
     // Each insert happens in its own query in the degenerate case.  However,
     // we wrap it in a transaction so that it is atomic where possible.  On many
     // databases, such as SQLite, this is also a notable performance boost.

modules/simpletest/tests/database_test.test

@@ -562,6 +562,24 @@ class DatabaseInsertDefaultsTestCase extends DatabaseTestCase {
     }
   }
 
+  /**
+   * Test that no action will be preformed if no fields are specified.
+   */
+  function testDefaultEmptyInsert() {
+    try {
+      $num_records_before = (int) db_query("SELECT COUNT(*) FROM {test}")->fetchField();
+
+      $result = db_insert('test')->execute();
+      $this->assertNull($result, t('Return NULL as no fields are specified.'));
+
+      $num_records_after = (int) db_query("SELECT COUNT(*) FROM {test}")->fetchField();
+      $this->assertIdentical($num_records_before, $num_records_after, t('Do nothing as no fields are specified.'));
+    }
+    catch (Exception $e) {
+      $this->assertTrue(FALSE, $e->getMessage());
+    }
+  }
+
   /**
    * Test that we can insert fields with values and defaults in the same query.
    */