diff --git a/api/src/Storage/RowsIterator.php b/api/src/Storage/RowsIterator.php
new file mode 100644
index 0000000000..dc5cf75af3
--- /dev/null
+++ b/api/src/Storage/RowsIterator.php
@@ -0,0 +1,188 @@
+<?php
+/**
+ * EGroupware generalized SQL Storage Object: Iterator for get_rows
+ *
+ * @license http://opensource.org/licenses/gpl-license.php GPL - GNU General Public License
+ * @package api
+ * @subpackage storage
+ * @link http://www.egroupware.org
+ * @author Ralf Becker <rb@egroupware.org>
+ * @copyright 2020 by Ralf Becker <rb@egroupware.org>
+ */
+
+namespace EGroupware\Api\Storage;
+use EGroupware\Api;
+
+/**
+ * Iterator using a get_rows method and querying it in chunks instead of all rows as once
+ *
+ * You should use a consisten sorting eg. by id, in case rows change while the iterator is instanciated!
+ *
+ * Instead of ($query['num_rows']=-1, $query['start']=0):
+ *
+ * $storage->get_rows($query, $rows, $readonlys);
+ *
+ * Use:
+ *
+ * $rows = new RowsIterator($storage, $query);
+ */
+class RowsIterator implements \Iterator
+{
+	/**
+	 * Reference of Storage\Base class or other object with a get_rows method
+	 *
+	 * @var Base
+	 */
+	protected $storage;
+
+	/**
+	 * query parameter for get_rows
+	 *
+	 * @var array
+	 */
+	protected $query;
+
+	/**
+	 * name of (unique) key in row or null to use $this->start + key returned by get_rows
+	 *
+	 * @var string
+	 */
+	protected $key;
+
+	/**
+	 * current chunk
+	 *
+	 * @var array
+	 */
+	protected $rows;
+
+	/**
+	 * Start value for callback
+	 *
+	 * @var int
+	 */
+	protected $start=0;
+
+	/**
+	 * Number of rows queried from get_rows in one call
+	 */
+	const CHUNK_SIZE = 500;
+
+	/**
+	 * Log calls via error_log()
+	 *
+	 * @var boolean
+	 */
+	public $debug = false;
+
+	/**
+	 * Constructor
+	 *
+	 * @param Base $storage only requirement is class to have a get_rows method
+	 * @param array $query query parameter for get_rows
+	 * @param string $key =null name of (unique) key in row, default use $this->start + key from get_rows
+	 */
+	public function __construct($storage, array $query, $key=null)
+	{
+		if (!is_object($storage) || !method_exists($storage, 'get_rows'))
+		{
+			throw new Api\Exception\WrongParameter("\$storage parameter needs to be object with a get_rows method!");
+		}
+		$this->storage = $storage;
+		$this->query = $query;
+		$this->key = $key;
+	}
+
+	/**
+	 * Return the current element
+	 *
+	 * @return array
+	 */
+	public function current()
+	{
+		if ($this->debug) error_log(__METHOD__."() returning ".array2string(current($this->rows)));
+		return current($this->rows);
+	}
+
+	/**
+	 * Return the key of the current element
+	 *
+	 * @return int|string
+	 */
+	public function key()
+	{
+		$current = current($this->rows);
+
+		$key = !empty($this->key) ? $current[$this->key] : $this->start + key($this->rows);
+		if ($this->debug) error_log(__METHOD__."() returning ".array2string($key));
+		return $key;
+	}
+
+	/**
+	 * Move forward to next element (called after each foreach loop)
+	 */
+	public function next()
+	{
+		if (next($this->rows) !== false)
+		{
+			if ($this->debug) error_log(__METHOD__."() returning TRUE");
+			return true;
+		}
+		// check if previous query gave less then CHUNK_SIZE entries --> we're done
+		if ($this->start && count($this->rows) < self::CHUNK_SIZE)
+		{
+			if ($this->debug) error_log(__METHOD__."() returning FALSE (no more entries)");
+			return false;
+		}
+		// try query further rows via get_rows method and store result in $this->rows
+		$readonlys = null;
+		$this->query['start'] = $this->start;
+		$this->query['num_rows'] = self::CHUNK_SIZE;
+		$this->storage->get_rows($this->query, $this->rows, $readonlys);
+
+		// remove non-rows returned (sel_options and the like, or leading false old eTemplate required)
+		foreach($this->rows as $key => $row)
+		{
+			if (!is_int($key) || !is_array($row))
+			{
+				unset($this->rows[$key]);
+			}
+		}
+
+		if (!is_array($this->rows) || !($entries = count($this->rows)))
+		{
+			if ($this->debug) error_log(__METHOD__."() returning FALSE (no more entries)");
+			return false;	// no further entries
+		}
+		$this->start += self::CHUNK_SIZE;
+		reset($this->rows);
+
+		if ($this->debug) error_log(__METHOD__."() this->start=$this->start, entries=$entries, count(this->files)=".count($this->rows)." returning ".array2string(current($this->rows) !== false));
+
+		return current($this->rows) !== false;
+	}
+
+	/**
+	 * Rewind the Iterator to the first element (called at beginning of foreach loop)
+	 */
+	public function rewind()
+	{
+		if ($this->debug) error_log(__METHOD__."()");
+
+		$this->start = 0;
+		$this->rows = [];
+		if (!$this->rows) $this->next();	// otherwise valid will return false and nothing get returned
+		reset($this->rows);
+	}
+
+	/**
+	 * Checks if current position is valid
+	 *
+	 * @return boolean
+	 */
+	public function valid ()
+	{
+		if ($this->debug) error_log(__METHOD__."() returning ".array2string(current($this->rows) !== false));
+		return current($this->rows) !== false;
+	}
+}