Hybrid e_tree_model flat lists or parent-children

e_tree_model is apparently used for flat lists as well as parent-child
relationships (trees). Trees are expected to be far smaller than possible flat
lists. Very large flat lists (10,000+ rows or greater) are rendered very slowly
because of the tree computation overhead.

This change figures out whether a flat list or a tree is requested and chooses
the appropriate code to run based on what is requested. Trees run the more
expensive code while flat lists are returned as-is.

In addition, the tree rendering code has been optimized. Optimizations:

* Unchanging tree node ID is set once instead of inside a foreach() loop
* The parent-child query is now sorted by the sort parent ID so that each move
  rows to tree nodes iteration doesn't have to run through every remaining row

Fixes: #3062

e107_handlers/admin_ui.php

@@ -4364,8 +4364,6 @@ class e_admin_controller_ui extends e_admin_controller
 	public function getParentChildQry($orderby=false)
 	{
 		return "SELECT SQL_CALC_FOUND_ROWS * FROM `#".$this->getTableName()."` ";
-		// Use the following return statement to break e107 native sorting but speed up tree creation by presorting for e_tree_model::arrayToTree()
-		#return "SELECT SQL_CALC_FOUND_ROWS * FROM `#".$this->getTableName()."` ORDER BY ".$this->getSortParent().", ".$this->getSortField();
 	}
 
 

e107_handlers/model_class.php

@@ -3337,26 +3337,8 @@ class e_tree_model extends e_front_model
 			$sql = e107::getDb($this->getParam('model_class', 'e_model'));
 			$this->_total = $sql->total_results = false;
 
-			// Workaround: Parse and modify db_query param for simulated pagination
+			if($rows = $this->getRows($sql))
-			$this->prepareSimulatedPagination();
-			// Workaround: Parse and modify db_query param for simulated custom ordering
-			$this->prepareSimulatedCustomOrdering();
-
-			if($sql->gen($this->getParam('db_query'), $this->getParam('db_debug') ? true : false))
 			{
-				$rows_tree = self::arrayToTree($sql->rows(),
-				                               $this->getParam('primary_field'),
-				                               $this->getParam('sort_parent'));
-				$rows = self::flattenTree($rows_tree,
-				                          $this->getParam('sort_field'),
-				                          $this->getParam('sort_order'));
-
-				// Simulated pagination
-				$rows = array_splice($rows,
-				                     (int) $this->getParam('db_limit_offset'),
-				                     ($this->getParam('db_limit_count') ? $this->getParam('db_limit_count') : count($rows))
-				                     );
-
 				foreach($rows as $tmp)
 				{
 					$tmp = new $class_name($tmp);
@@ -3387,6 +3369,51 @@ class e_tree_model extends e_front_model
 		return $this;
 	}
 
+	protected function getRows($sql)
+	{
+		// Tree (Parent-Child Relationship)
+		if ($this->getParam('sort_parent') && $this->getParam('sort_field'))
+		{
+			return $this->getRowsTree($sql);
+		}
+		// Flat List
+		return $this->getRowsList($sql);
+	}
+
+	protected function getRowsList($sql)
+	{
+		$success = $sql->gen($this->getParam('db_query'), $this->getParam('db_debug') ? true : false);
+		if (!$success) return false;
+
+		return $sql->rows();
+	}
+
+	protected function getRowsTree($sql)
+	{
+		// Workaround: Parse and modify db_query param for simulated pagination
+		$this->prepareSimulatedPagination();
+		// Workaround: Parse and modify db_query param for simulated custom ordering
+		$this->prepareSimulatedCustomOrdering();
+
+		$success = $sql->gen($this->getParam('db_query'), $this->getParam('db_debug') ? true : false);
+		if (!$success) return false;
+
+		$rows_tree = self::arrayToTree($sql->rows(),
+			$this->getParam('primary_field'),
+			$this->getParam('sort_parent'));
+		$rows = self::flattenTree($rows_tree,
+			$this->getParam('sort_field'),
+			$this->getParam('sort_order'));
+
+		// Simulated pagination
+		$rows = array_splice($rows,
+			(int) $this->getParam('db_limit_offset'),
+			($this->getParam('db_limit_count') ? $this->getParam('db_limit_count') : count($rows))
+		);
+
+		return $rows;
+	}
+
 	/**
 	 * Converts a relational array with a parent field and a sort order field to a tree
 	 * @param array $rows Relational array with a parent field and a sort order field
@@ -3420,19 +3447,23 @@ class e_tree_model extends e_front_model
 	{
 		$node = &$nodes[0];
 		array_shift($nodes);
+		$nodeID = (int) $node[$primary_field];
 		foreach($rows as $key => $row)
 		{
-			$nodeID      = (int) $node[$primary_field];
 			$rowParentID = (int) $row[$sort_parent];
-			if($nodeID === $rowParentID)
+
+			// Note: This optimization only works if the SQL query executed was ordered by the sort parent.
+			if($nodeID !== $rowParentID)
 			{
+				break;
+			}
+
 			$node['_children'][] = &$row;
 			unset($rows[$key]);
 			$nodes[] = &$row;
 			unset($row);
 		}
 	}
-	}
 
 	/**
 	 * Flattens a tree into a depth-first array, sorting each node by a field's values
@@ -3569,7 +3600,7 @@ class e_tree_model extends e_front_model
 		$db_query = $this->getParam('db_query');
 		$db_query = preg_replace_callback('/ORDER BY (?:.+\.)*[\.]*([A-Za-z0-9$_,]+)[ ]*(ASC|DESC)*/i', function($matches)
 			{
-			if (isset($matches[1]))
+				if (!empty($matches[1]))
 				{
 					$current_sort_field = $this->getParam('sort_field');
 					if (!empty($current_sort_field))
@@ -3578,11 +3609,16 @@ class e_tree_model extends e_front_model
 					}
 					$this->setParam('sort_field', array_map('trim', explode(',', $matches[1])));
 				}
-			if (isset($matches[2]))
+				if (!empty($matches[2]))
 					$this->setParam('sort_order',
 						(0 === strcasecmp($matches[2], 'DESC') ? -1 : 1)
 					);
-		}, $db_query);
+
+				return "";
+			}, $db_query)
+			// Optimization goes with e_tree_model::moveRowsToTreeNodes()
+			. " ORDER BY " . $this->getParam('sort_parent') . ", " . $this->getParam('sort_field');
+		$this->setParam('db_query', $db_query);
 	}
 
 	/**