- Patch #575360 by dropcube: added API function to check if a cache bin is empty.

includes/cache-install.inc

@@ -28,5 +28,8 @@ function set($cid, $data, $expire = CACHE_PERMANENT, array $headers = NULL) {
 
   function clear($cid = NULL, $wildcard = FALSE) {
   }
-	
+
+  function isEmpty() {
+    return TRUE;
+  }
 }

includes/cache.inc

@@ -167,6 +167,21 @@ function cache_clear_all($cid = NULL, $bin = NULL, $wildcard = FALSE) {
   return _cache_get_object($bin)->clear($cid, $wildcard);
 }
 
+/**
+ * Check if a cache bin is empty.
+ *
+ * A cache bin is considered empty if it does not contain any valid data for any
+ * cache ID.
+ *
+ * @param $bin
+ *   The cache bin to check.
+ * @return
+ *   TRUE if the cache bin specified is empty.
+ */
+function cache_is_empty($bin) {
+  return _cache_get_object($bin)->isEmpty();
+}
+
 /**
  * Interface for cache implementations.
  *
@@ -260,6 +275,17 @@ function set($cid, $data, $expire = CACHE_PERMANENT, array $headers = NULL);
    *   match. If '*' is given as $cid, the bin $bin will be emptied.
    */
   function clear($cid = NULL, $wildcard = FALSE);
+
+  /**
+   * Check if a cache bin is empty.
+   *
+   * A cache bin is considered empty if it does not contain any valid data for
+   * any cache ID.
+   *
+   * @return
+   *   TRUE if the cache bin specified is empty.
+   */
+  function isEmpty();
 }
 
 /**
@@ -449,4 +475,14 @@ function clear($cid = NULL, $wildcard = FALSE) {
       }
     }
   }
+
+  function isEmpty() {
+    $this->garbageCollection();
+    $query = db_select($this->bin);
+    $query->addExpression('1');
+    $result = $query->range(0, 1)
+      ->execute()
+      ->fetchField();
+    return empty($result);
+  }
 }

modules/simpletest/tests/cache.test

@@ -312,3 +312,40 @@ class CacheClearCase extends CacheTestCase {
                        t('All cache entries removed when the array exceeded the cache clear threshold.'));
   }
 }
+
+/**
+ * Test cache_is_empty() function.
+ */
+class CacheIsEmptyCase extends CacheTestCase {
+  public static function getInfo() {
+    return array(
+      'name' => 'Cache emptiness test',
+      'description' => 'Check if a cache bin is empty after performing clear operations.',
+      'group' => 'Cache'
+    );
+  }
+
+  function setUp() {
+    $this->default_bin = 'cache_page';
+    $this->default_value = $this->randomName(10);
+
+    parent::setUp();
+  }
+
+  /**
+   * Test clearing using a cid.
+   */
+  function testIsEmpty() {
+    // Clear the cache bin.
+    cache_clear_all('*', $this->default_bin);
+    $this->assertTrue(cache_is_empty($this->default_bin), t('The cache bin is empty'));
+    // Add some data to the cache bin.
+    cache_set($this->default_cid, $this->default_value, $this->default_bin);
+    $this->assertCacheExists(t('Cache was set.'), $this->default_value, $this->default_cid);
+    $this->assertFalse(cache_is_empty($this->default_bin), t('The cache bin is not empty'));
+    // Remove the cached data.
+    cache_clear_all($this->default_cid, $this->default_bin);
+    $this->assertCacheRemoved(t('Cache was removed.'), $this->default_cid);
+    $this->assertTrue(cache_is_empty($this->default_bin), t('The cache bin is empty'));
+  }
+}