Merge lp:~quam-plures-core/quam-plures/bug-523401 into lp:quam-plures

[Tilman Blumenbach]

[lp:~quam-plures-core/quam-plures/bug-523401]

7436. By Tilman Blumenbach on 2010-02-21

Correctly commit DB changes

[EdB (edb)]

Tested without issue, assuming one accepts the smilies bug as not an issue due to it has been fixed. Which I do. Accept that condition I mean. Hey look: they give me this big giant textarea so what am I gonna do with it?

Approve it in one line?

review: Approve

=== modified file 'inc/_core/_misc.funcs.php'
--- inc/_core/_misc.funcs.php	2010-02-17 18:59:03 +0000
+++ inc/_core/_misc.funcs.php	2010-02-21 13:58:12 +0000
@@ -72,9 +72,12 @@
 }
 
 /**
+ * Get a cache reference.
+ *
  * @todo fp> split into 1 function per case. (typed @return values)
- *
- * @return DataObjectCache
+ * 
+ * @param string The cache to get (see source code for possible names).
+ * @return mixed The requested cache (debug_die()s on invalid cache name).
  */
 function & get_Cache( $objectName )
 {
@@ -138,6 +141,10 @@
 			$ItemTagsCache = array();
 			return $ItemTagsCache;
 
+		case 'ItemCatsCache':
+			$ItemCatsCache = array();
+			return $ItemCatsCache;
+
 		case 'ItemStatusCache':
 			$Plugins->get_object_from_cacheplugin_or_create( 'ItemStatusCache', 'new GenericCache( \'GenericElement\', true, \'T_items__status\', \'pst_\', \'pst_ID\', NULL, \'\', T_(\'No status\') )' );
 			return $ItemStatusCache;
@@ -3325,4 +3332,22 @@
 }
 
 
+/**
+ * Check if two arrays contain the same elements.
+ *
+ * @param array    The first array.
+ * @param array    The second array.
+ * @return boolean True if both arrays contain the same elements, false
+ *                 otherwise.
+ */
+function array_equal( $one, $two )
+{
+	$one_count = count( $one );
+
+	/* We consider the arrays to be equal if they have the same number of
+	 * elements and all elements of $one are present in $two.
+	 */
+	return $one_count == count( $two ) &&
+				count( array_intersect( $one, $two ) ) == $one_count;
+}
 ?>

=== modified file 'inc/collections/model/_category.funcs.php'
--- inc/collections/model/_category.funcs.php	2009-12-19 19:51:52 +0000
+++ inc/collections/model/_category.funcs.php	2010-02-21 13:58:12 +0000
@@ -78,36 +78,6 @@
 
 
 /**
- * Get category name+blog_id for specified cat ID
- *
- * fplanque: reused "R. U. Serious" optimization here
- * fplanque: added blog ID stuff
- *
- * @deprecated since 3.1.0-alpha. Use ChapterCache instead.
- * @param integer category ID
- * @param boolean die() if category does not exist? (default: true)
- *
- */
-function get_the_category_by_ID( $cat_ID, $die = true )
-{
-	global $cache_categories;
-	if( empty($cache_categories[$cat_ID]) )
-	{
-		cat_load_cache( 'none' );
-	}
-	if( !isset( $cache_categories[$cat_ID] ) )
-	{
-		if( $die )
-		{
-			debug_die( sprintf( T_('Requested category %s does not exist!'),  $cat_ID ) );
-		}
-		else return false;
-	}
-	return $cache_categories[$cat_ID];
-}
-
-
-/**
  * Get blog ID for a given cat.
  * This halts on error.
  * @return integer
@@ -194,55 +164,6 @@
 
 
 /**
- * Load cache for category associations with current posts
- *
- * @todo put this into main post query when MySQL 4.0 commonly available
- * @todo dh> why is this limited to the _global_ $postIDlist?!
- *           Really ridiculous, trying to get a list of category names for an Item (which is not in $postIDlist for example.. :/)
- * fp> This is legacy from a quick b2/cafelog hack. This will de deprecated.
- * dh> Only used in ItemLight::get_Chapters now - move it there for now? fp> no it should stay close to $cache_postcats handling until teh whole thing dies.
- */
-function cat_load_postcats_cache()
-{
-	global $DB, $cache_postcats, $postIDlist, $preview;
-
-	if( isset($cache_postcats) )
-	{ // already done!
-		return;
-	}
-
-	if( $preview )
-	{ // Preview mode
-		global $extracats, $post_category;
-		param( 'extracats', 'array', array() );
-		if( !in_array( $post_category, $extracats ) )
-			$extracats[] = $post_category;
-		$cache_postcats[0] = $extracats;
-		return;
-	}
-
-	if( !empty($postIDlist) )
-	{
-		$sql = "SELECT postcat_post_ID, postcat_cat_ID
-						FROM T_postcats
-						WHERE postcat_post_ID IN ($postIDlist)
-						ORDER BY postcat_post_ID, postcat_cat_ID";
-
-		foreach( $DB->get_results( $sql, ARRAY_A ) as $myrow )
-		{
-			$postcat_post_ID = $myrow["postcat_post_ID"];
-			if( ! isset( $cache_postcats[$postcat_post_ID] ) )
-			{
-				 $cache_postcats[$postcat_post_ID] = array();
-			}
-			$cache_postcats[$postcat_post_ID][] = $myrow["postcat_cat_ID"];
-			// echo "just cached: post=$postcat_post_ID  cat=".$myrow["postcat_cat_ID"]."<br />";
-		}
-	}
-}
-
-
-/**
  * Get category associations with given post
  */
 function postcats_get_byID( $post_ID )
@@ -471,4 +392,4 @@
 {
 }
 
-?>
\ No newline at end of file
+?>

=== modified file 'inc/items/items.ctrl.php'
--- inc/items/items.ctrl.php	2010-02-02 02:56:23 +0000
+++ inc/items/items.ctrl.php	2010-02-21 13:58:12 +0000
@@ -302,7 +302,7 @@
 		$current_User->check_perm( 'item_post!CURSTATUS', 'edit', true, $edited_Item );
 
 		$post_comment_status = $edited_Item->get( 'comment_status' );
-		$post_extracats = postcats_get_byID( $p ); // NOTE: dh> using $edited_Item->get_Chapters here instead fails (empty list, since no postIDlist).
+		$post_extracats = $edited_Item->get_Chapter_IDs();
 
 		$item_tags = implode( ', ', $edited_Item->get_tags() );
 		$trackback_url = '';
@@ -456,6 +456,13 @@
 		// Is this post already published?
 		$was_published = $edited_Item->status == 'published';
 
+		// Load tags and extra categories to allow the system to check
+		// whether they have been changed. While this could look like
+		// "yet another unnecessary SQL query", it prevents deleting all
+		// the tags/categories just to insert the same all over data again.
+		$edited_Item->get_tags();
+		$edited_Item->get_Chapter_IDs();
+
 		// UPDATE POST:
 		// Set the params we already got:
 		$edited_Item->set( 'status', $post_status );

=== modified file 'inc/items/model/_item.class.php'
--- inc/items/model/_item.class.php	2010-02-21 05:04:49 +0000
+++ inc/items/model/_item.class.php	2010-02-21 13:58:12 +0000
@@ -183,13 +183,6 @@
 	var $notifications_ctsk_ID;
 
 	/**
-	 * array of IDs or NULL if we don't know...
-	 *
-	 * @var array
-	 */
-	var $extra_cat_IDs = NULL;
-
-	/**
 	 * Array of tags (strings)
 	 *
 	 * Lazy loaded.
@@ -199,6 +192,13 @@
 	var $tags = NULL;
 
 	/**
+	 * Records whether $tags differs from the value stored in the DB.
+	 *
+	 * @var boolean
+	 */
+	var $tags_changed = false;
+
+	/**
 	 * Array of Links attached to this item.
 	 *
 	 * NULL when not initialized.
@@ -1538,28 +1538,52 @@
 	/**
 	 * Split tags by comma or semicolon
 	 *
+	 * @todo Tblue> Check whether a change should invalidate the ItemTagsCache
+	 *              for this Item.
+	 * 
 	 * @param string The tags, separated by comma or semicolon
+	 * @return boolean True if the tags have been changed, false otherwise.
 	 */
 	function set_tags_from_string( $tags )
 	{
-		if( $tags === '' )
-		{
-			$this->tags = array();
-			return;
-		}
-		$this->tags = preg_split( '/\s*[;,]+\s*/', $tags, -1, PREG_SPLIT_NO_EMPTY );
-
+		$tags_arr = preg_split( '/\s*[;,]+\s*/', $tags, -1, PREG_SPLIT_NO_EMPTY );
+		
 		if( function_exists( 'mb_strtolower' ) )
-		{	// fp> TODO: instead of those "when used" ifs, it would make more sense to redefine mb_strtolower beforehand if it doesn"t exist (it would then just be a fallback to the strtolower + a Debuglog->add() )
-			// Tblue> Note on charset: param() should have converted the tag string from $io_charset to $evo_charset.
-			array_walk( $this->tags, create_function( '& $tag', '$tag = mb_strtolower( $tag, $GLOBALS[\'evo_charset\'] );' ) );
+		{	// fp> TODO: instead of those "when used" ifs, it would make
+			//           more sense to redefine mb_strtolower beforehand
+			//           if it doesn't exist (it would then just be a
+			//           fallback to the strtolower + a Debuglog->add() )
+			// Tblue> Note on charset: param() should have converted the
+			//        tag string from $io_charset to $evo_charset.
+			array_walk( $tags_arr, create_function( '& $tag',
+				'$tag = mb_strtolower( $tag, $GLOBALS[\'evo_charset\'] );' ) );
 		}
 		else
 		{
-			array_walk( $this->tags, create_function( '& $tag', '$tag = strtolower( $tag );' ) );
-		}
-		$this->tags = array_unique( $this->tags );
-		// pre_dump( $this->tags );
+			array_walk( $tags_arr, create_function( '& $tag', '$tag = strtolower( $tag );' ) );
+		}
+
+		$tags_arr = array_unique( $tags_arr );
+
+		/* If there are no previous tags defined (Item::tags equals NULL),
+		 * we do not check for changes and just set the new tags.
+		 * Otherwise, if $tags contains the same elements as Item::tags,
+		 * no update is necessary.
+		 */
+		if( $this->tags !== NULL && array_equal( $tags_arr, $this->tags ) )
+		{	// No changes.
+			/* Note: We do not update Item::tags_changed here because it
+			 * could be set to true by a previous call to this method.
+			 */
+			return false;
+		}
+
+		// Only set Item::tags_changed to true if there were no previous
+		// tags defined:
+		$this->tags_changed = $this->tags !== NULL;
+		$this->tags         = $tags_arr;
+
+		return true;
 	}
 
 
@@ -3307,18 +3331,19 @@
 
 		if( ( $result = parent::dbupdate( $auto_track_modification ) ) !== false )
 		{ // We could update the item object:
-
 			// Let's handle the extracats:
-			$this->insert_update_extracats( 'update' );
-
+			$excats_updated = $this->insert_update_extracats( 'update' );
 			// Let's handle the tags:
-			$this->insert_update_tags( 'update' );
+			$tags_updated   = $this->insert_update_tags( 'update' );
 
-			$this->delete_prerendered_content();
+			if( $result !== NULL || $excats_updated || $tags_updated )
+			{	// We need to delete the prerendered content:
+				$this->delete_prerendered_content();
+			}
 
 			$DB->commit();
 
-			$Plugins->trigger_event( 'AfterItemUpdate', $params = array( 'Item' => & $this, 'dbchanges' => $dbchanges ) );
+			$Plugins->trigger_event( 'AfterItemUpdate', array( 'Item' => & $this, 'dbchanges' => $dbchanges ) );
 		}
 		else
 		{
@@ -3405,29 +3430,39 @@
 	{
 		global $DB;
 
+		if( $this->extra_cat_IDs === NULL )
+		{	// Cannot insert/update non-defined tags:
+			return false;
+		}
+
 		$DB->begin();
 
-		if( ! is_null( $this->extra_cat_IDs ) )
-		{ // Okay the extra cats are defined:
-
-			if( $mode == 'update' )
-			{
-				// delete previous extracats:
-				$DB->query( 'DELETE FROM T_postcats WHERE postcat_post_ID = '.$this->ID, 'delete previous extracats' );
-			}
-
-			// insert new extracats:
-			$query = "INSERT INTO T_postcats( postcat_post_ID, postcat_cat_ID ) VALUES ";
-			foreach( $this->extra_cat_IDs as $extra_cat_ID )
-			{
-				//echo "extracat: $extracat_ID <br />";
-				$query .= "( $this->ID, $extra_cat_ID ),";
-			}
-			$query = substr( $query, 0, strlen( $query ) - 1 );
-			$DB->query( $query, 'insert new extracats' );
-		}
+		if( $mode == 'update' )
+		{
+			if( ! $this->extra_cat_IDs_changed )
+			{	// No update necessary:
+				$DB->commit();
+				return false;
+			}
+
+			$this->extra_cat_IDs_changed = false;
+
+			// delete previous extracats:
+			$DB->query( 'DELETE FROM T_postcats WHERE postcat_post_ID = '.$this->ID, 'delete previous extracats' );
+		}
+
+		// insert new extracats:
+		$query = "INSERT INTO T_postcats( postcat_post_ID, postcat_cat_ID ) VALUES ";
+		foreach( $this->extra_cat_IDs as $extra_cat_ID )
+		{
+			//echo "extracat: $extracat_ID <br />";
+			$query .= "( $this->ID, $extra_cat_ID ),";
+		}
+		$query = substr( $query, 0, strlen( $query ) - 1 );
+		$DB->query( $query, 'insert new extracats' );
 
 		$DB->commit();
+		return true;
 	}
 
 
@@ -3440,50 +3475,63 @@
 	{
 		global $DB;
 
-		if( isset( $this->tags ) )
-		{ // Okay the tags are defined:
-
-			$DB->begin();
-
-			if( $mode == 'update' )
-			{	// delete previous tag associations:
-				// Note: actual tags never get deleted
-				$DB->query( 'DELETE FROM T_items__itemtag
-											WHERE itag_itm_ID = '.$this->ID, 'delete previous tags' );
+		if( $this->tags === NULL )
+		{	// Cannot update/insert non-defined tags.
+			return false;
+		}
+
+		$DB->begin();
+
+		if( $mode == 'update' )
+		{
+			if( ! $this->tags_changed )
+			{	// Tags have not been changed, no update necessary.
+				$DB->commit();
+				return false;
 			}
 
-			if( !empty($this->tags) )
-			{
-				// Find the tags that are already in the DB
-				$query = 'SELECT LOWER( tag_name )
-										FROM T_items__tag
-									 WHERE tag_name IN ('.$DB->quote($this->tags).')';
-				$existing_tags = $DB->get_col( $query, 0, 'Find existing tags' );
-
-				$new_tags = array_diff( $this->tags, $existing_tags );
-				//pre_dump($new_tags);
-
-				if( !empty( $new_tags ) )
-				{	// insert new tags:
-					$query = "INSERT INTO T_items__tag( tag_name ) VALUES ";
-					foreach( $new_tags as $tag )
-					{
-						$query .= '( '.$DB->quote($tag).' ),';
-					}
-					$query = substr( $query, 0, strlen( $query ) - 1 );
-					$DB->query( $query, 'insert new tags' );
+			$this->tags_changed = false;
+
+			// delete previous tag associations:
+			// Note: actual tags never get deleted
+			// Tblue> TODO: We should probably provide some mechanism to
+			//              delete old (unused) tags.
+			$DB->query( 'DELETE FROM T_items__itemtag
+										WHERE itag_itm_ID = '.$this->ID, 'delete previous tags' );
+		}
+
+		if( !empty($this->tags) )
+		{
+			// Find the tags that are already in the DB
+			$query = 'SELECT LOWER( tag_name )
+									FROM T_items__tag
+								 WHERE tag_name IN ('.$DB->quote($this->tags).')';
+			$existing_tags = $DB->get_col( $query, 0, 'Find existing tags' );
+
+			$new_tags = array_diff( $this->tags, $existing_tags );
+			//pre_dump($new_tags);
+
+			if( !empty( $new_tags ) )
+			{	// insert new tags:
+				$query = "INSERT INTO T_items__tag( tag_name ) VALUES ";
+				foreach( $new_tags as $tag )
+				{
+					$query .= '( '.$DB->quote($tag).' ),';
 				}
-
-				// ASSOC:
-				$query = 'INSERT INTO T_items__itemtag( itag_itm_ID, itag_tag_ID )
-								  SELECT '.$this->ID.', tag_ID
-									  FROM T_items__tag
-									 WHERE tag_name IN ('.$DB->quote($this->tags).')';
-				$DB->query( $query, 'Make tag associations!' );
+				$query = substr( $query, 0, strlen( $query ) - 1 );
+				$DB->query( $query, 'insert new tags' );
 			}
 
-			$DB->commit();
+			// ASSOC:
+			$query = 'INSERT INTO T_items__itemtag( itag_itm_ID, itag_tag_ID )
+							  SELECT '.$this->ID.', tag_ID
+								  FROM T_items__tag
+								 WHERE tag_name IN ('.$DB->quote($this->tags).')';
+			$DB->query( $query, 'Make tag associations!' );
 		}
+
+		$DB->commit();
+		return true;
 	}
 
 
@@ -3992,32 +4040,5 @@
 		}
 		return $r;
 	}
-
-
-	/**
-	 * Get a list of item IDs from $MainList and $ItemList, if they are loaded.
-	 * This is used for prefetching item related data for the whole list(s).
-	 * This will at least return the item's ID itself.
-	 * @return array
-	 */
-	function get_prefetch_itemlist_IDs()
-	{
-		global $MainList, $ItemList;
-
-		// Add the current ID to the list to prefetch, if it's not in the MainList/ItemList (e.g. featured item).
-		$r = array($this->ID);
-
-		if( $MainList )
-		{
-			$r = array_merge($r, $MainList->get_page_ID_array());
-		}
-		if( $ItemList )
-		{
-			$r = array_merge($r, $ItemList->get_page_ID_array());
-		}
-		return $r;
-	}
 }
-
-
 ?>

=== modified file 'inc/items/model/_itemlight.class.php'
--- inc/items/model/_itemlight.class.php	2010-02-17 18:34:51 +0000
+++ inc/items/model/_itemlight.class.php	2010-02-21 13:58:12 +0000
@@ -75,6 +75,7 @@
 	 * @var integer
 	 */
 	var $main_cat_ID = 0;
+
 	/**
 	 * @var Chapter
 	 * @access protected
@@ -83,6 +84,21 @@
 	var $main_Chapter;
 
 	/**
+	 * array of IDs or NULL if we don't know...
+	 *
+	 * @var array
+	 */
+	var $extra_cat_IDs = NULL;
+
+	/**
+	 * Records whether $extra_cat_IDs differs from the value stored in the
+	 * DB.
+	 *
+	 * @var boolean
+	 */
+	var $extra_cat_IDs_changed = false;
+
+	/**
 	 * Derived from $main_cat_ID.
 	 *
 	 * @var integer
@@ -150,6 +166,8 @@
 			$this->issue_date = $db_row->post_datestart;
 			$this->datestart = $db_row->post_datestart;
 			$this->mod_date = $db_row->post_datemodified;
+			// Note: DO NOT use ItemLight::set() to set the main category
+			//       ID here, it will confuse ItemLight::set_extracats().
 			$this->main_cat_ID = $db_row->post_main_cat_ID;
 			$this->urltitle = $db_row->post_urltitle;
 			$this->title = $db_row->post_title;
@@ -458,28 +476,60 @@
 
 
 	/**
+	 * Get the chapter (category) IDs for this item.
+	 *
+	 * Loads the extra categories and populates ItemLight::extra_cat_IDs
+	 * if necessary.
+	 * This method automatically populates the ItemCatsCache for other
+	 * posts in the item list.
+	 *
+	 * @return array The category IDs.
+	 */
+	function get_Chapter_IDs()
+	{
+		global $DB;
+
+		if( $this->extra_cat_IDs === NULL )
+		{
+			$ItemCatsCache = & get_Cache( 'ItemCatsCache' );
+
+			if( ! isset( $ItemCatsCache[$this->ID] ) )
+			{	// Load this post's categories and fetch category associations
+				// for other posts in the item list.
+				// Only prefetch data for the IDs which are not yet in the cache:
+				$prefetch_IDs = array_diff( $this->get_prefetch_itemlist_IDs(),
+									array_keys( $ItemCatsCache ) );
+
+				// This *should* return at least the main category for each post.
+				foreach( $DB->get_results( '
+							SELECT postcat_post_ID, postcat_cat_ID
+								FROM T_postcats
+							WHERE postcat_post_ID IN ('.$DB->quote( $prefetch_IDs ).')
+							ORDER BY postcat_post_ID, postcat_cat_ID', OBJECT,
+							'Get category associations' ) as $row )
+				{
+					$ItemCatsCache[$row->postcat_post_ID][] = $row->postcat_cat_ID;
+				}
+			}
+
+			$this->extra_cat_IDs = $ItemCatsCache[$this->ID];
+		}
+
+		return $this->extra_cat_IDs;
+	}
+
+
+	/**
 	 * Get list of Chapter objects.
 	 *
 	 * @return array of {@link Chapter chapters} (references)
 	 */
 	function get_Chapters()
 	{
-		global $cache_postcats;
-
 		$ChapterCache = & get_Cache( 'ChapterCache' );
 
-		// Load cache for category associations with current posts
-		// TODO: dh> This fails, if $postIDlist is not set! (e.g. in admin)
-		cat_load_postcats_cache();
-
-		if( isset($cache_postcats[$this->ID]) )
-		{ // dh> may not be set! (demo logs)
-			$categoryIDs = $cache_postcats[$this->ID];
-		}
-		else $categoryIDs = array();
-
 		$chapters = array();
-		foreach( $categoryIDs as $cat_ID )
+		foreach( $this->get_Chapter_IDs() as $cat_ID )
 		{
 			$chapters[] = & $ChapterCache->get_by_ID( $cat_ID );
 		}
@@ -924,6 +974,73 @@
 
 
 	/**
+	 * Set the extra categories for this item.
+	 *
+	 * NOTE: Use ItemLight::set( 'extra_cat_IDs', ... ) to set the extra
+	 * categories.
+	 *
+	 * @todo Tblue> Check whether a change should invalidate the ItemCatsCache
+	 *              for this Item.
+	 * 
+	 * @param array   An array containing the extra category IDs.
+	 * @param boolean Whether to add the new categories to the existing
+	 *                ones.
+	 * @return boolean True if the extra categories have changed.
+	 */
+	function set_extracats( $cats, $add = false )
+	{
+		global $Debuglog;
+
+		$cats = array_unique( $cats );
+
+/*
+		$Debuglog->add( 'set_extracats(): Old cats = '.var_export( $this->extra_cat_IDs, true )
+					   .'; new cats = '.var_export( $cats, true ).'; $add = '.(int)$add,
+							'dataobjects' );
+*/
+
+		/* If there are no previous categories(ItemLight::extra_cat_IDs
+		 * equals NULL), we don't check whether there were changes, but
+		 * simply set the supplied categories (see below).
+		 * Otherwise, if $add is false, we check whether the $cats array
+		 * contains the same elements as ItemLight::extra_cat_IDs; if $add
+		 * is true, we check whether there are no new elements in $cats.
+		 * If one of the two conditions above is true, the extra categories
+		 * do not need to be updated.
+		 */
+		if( $this->extra_cat_IDs !== NULL && (
+				( ! $add && array_equal( $cats, $this->extra_cat_IDs ) ) ||
+				( $add && ! ( $added = array_diff( $cats, $this->extra_cat_IDs ) ) )
+			) )
+		{	// No update necessary.
+			/* Note: We do not update ItemLight::extra_cat_IDs_changed here
+			 * because it could be set to true by a previous call to this
+			 * method.
+			 */
+			//$Debuglog->add( 'set_extracats(): Not updating.', 'dataobjects' );
+			return false; // no changes
+		}
+
+		// Only set ItemLight::extra_cat_IDs_changed to true if there
+		// were no previous extra categories defined:
+		$this->extra_cat_IDs_changed = $this->extra_cat_IDs !== NULL;
+
+		// If there were no previous categories or we do not want to add
+		// the supplied categories to the existing ones:
+		if( $this->extra_cat_IDs === NULL || ! $add )
+		{	// Simply override the old cats:
+			$this->extra_cat_IDs = $cats;
+		}
+		else
+		{	// Add the new categories:
+			$this->extra_cat_IDs = array_merge( $this->extra_cat_IDs, $added );
+		}
+		
+		return true; // There were changes.
+	}
+
+
+	/**
 	 * Set param value
 	 *
 	 * By default, all values will be considered strings
@@ -941,24 +1058,25 @@
 		{
 			case 'main_cat_ID':
 				$r = $this->set_param( 'main_cat_ID', 'number', $parvalue, false );
-				// make sure main cat is in extracat list and there are no duplicates
-				$this->extra_cat_IDs[] = $this->main_cat_ID;
-				$this->extra_cat_IDs = array_unique( $this->extra_cat_IDs );
+
+				// Make sure main cat is in extracat list:
+				$this->set_extracats( array( $this->main_cat_ID ), true );
+
 				// Invalidate derived property:
 				$this->blog_ID = NULL;
-				unset($this->main_Chapter); // dereference
+
+				unset($this->main_Chapter); // remove reference
 				$this->main_Chapter = NULL;
-				unset($this->Blog);
+
+				unset($this->Blog); // remove reference
 				$this->Blog = NULL;
+
 				return $r;
 
 			case 'extra_cat_IDs':
-				// ARRAY! We do not record this change (yet)
-				$this->extra_cat_IDs = $parvalue;
-				// make sure main cat is in extracat list and there are no duplicates
-				$this->extra_cat_IDs[] = $this->main_cat_ID;
-				$this->extra_cat_IDs = array_unique( $this->extra_cat_IDs );
-				break;
+				// ARRAY. Make sure main cat is in extracat list:
+				$parvalue[] = $this->main_cat_ID;
+				return $this->set_extracats( $parvalue );
 
 			case 'issue_date':
 			case 'datestart':
@@ -1004,7 +1122,30 @@
 		}
 	}
 
+
+	/**
+	 * Get a list of item IDs from $MainList and $ItemList, if they are loaded.
+	 * This is used for prefetching item related data for the whole list(s).
+	 * This will at least return the item's ID itself.
+	 * @return array
+	 */
+	function get_prefetch_itemlist_IDs()
+	{
+		global $MainList, $ItemList;
+
+		// Add the current ID to the list to prefetch, if it's not in the MainList/ItemList (e.g. featured item).
+		$r = array($this->ID);
+
+		if( $MainList )
+		{
+			$r = array_merge($r, $MainList->get_page_ID_array());
+		}
+		if( $ItemList )
+		{
+			$r = array_merge($r, $ItemList->get_page_ID_array());
+		}
+
+		return array_unique( $r );
+	}
 }
-
-
 ?>