Issue #1145080 by David_Rothstein, Noe_, drewish, hosef, bigjim: Fixed SelectQuery::countQuery() incompatible with UNION queries.

core/lib/Drupal/Core/Database/Query/Select.php

@@ -582,7 +582,25 @@ class Select extends Query implements SelectInterface {
     return $this;
   }
 
+  /**
+   * Implements SelectInterface::countQuery().
+   */
   public function countQuery() {
+    $count = $this->prepareCountQuery();
+
+    $query = $this->connection->select($count);
+    $query->addExpression('COUNT(*)');
+
+    return $query;
+  }
+
+  /**
+   * Prepares a count query from the current query object.
+   *
+   * @return Drupal\Core\Database\Query\Select
+   *   A new query object ready to have COUNT(*) performed on it.
+   */
+  protected function prepareCountQuery() {
     // Create our new query object that we will mutate into a count query.
     $count = clone($this);
 
@@ -630,10 +648,13 @@ class Select extends Query implements SelectInterface {
       $count->distinct = FALSE;
     }
 
-    $query = $this->connection->select($count);
+    // If there are any dependent queries to UNION, prepare each of those for
-    $query->addExpression('COUNT(*)');
+    // the count query also.
+    foreach ($count->union as &$union) {
+      $union['query'] = $union['query']->prepareCountQuery();
+    }
 
-    return $query;
+    return $count;
   }
 
   public function __toString() {

core/modules/system/lib/Drupal/system/Tests/Database/SelectTest.php

@@ -281,6 +281,28 @@ class SelectTest extends DatabaseTestBase {
     $this->assertEqual($names[2], 'Ringo', 'Third query returned correct name.');
   }
 
+  /**
+   * Tests that we can get a count query for a UNION Select query.
+   */
+  function testUnionCount() {
+    $query_1 = db_select('test', 't')
+      ->fields('t', array('name', 'age'))
+      ->condition('age', array(27, 28), 'IN');
+
+    $query_2 = db_select('test', 't')
+      ->fields('t', array('name', 'age'))
+      ->condition('age', 28);
+
+    $query_1->union($query_2, 'ALL');
+    $names = $query_1->execute()->fetchCol();
+
+    $query_3 = $query_1->countQuery();
+    $count = $query_3->execute()->fetchField();
+
+    // Ensure the counts match.
+    $this->assertEqual(count($names), $count, "The count query's result matched the number of rows in the UNION query.");
+  }
+
   /**
    * Test that random ordering of queries works.
    *