PMCORE-949 Use of buffered query on cron's calculate parameter/task exhausts php's memory limit

workflow/engine/src/ProcessMaker/Util/BatchProcessWithIndexes.php

@@ -0,0 +1,57 @@
+<?php
+
+namespace ProcessMaker\Util;
+
+class BatchProcessWithIndexes
+{
+    /**
+     * Start of the query.
+     * @var int
+     */
+    private $start = 0;
+
+    /**
+     * Limit of the query.
+     * @var int
+     */
+    private $limit = 1000;
+
+    /**
+     * Total size of the query.
+     * @var int
+     */
+    private $size = 0;
+
+    /**
+     * Constructor of the class.
+     * @param int $size
+     */
+    public function __construct(int $size)
+    {
+        $this->size = $size;
+    }
+
+    /**
+     * Set custom limit of the query.
+     * @param int $limit
+     * @return self
+     */
+    public function setLimit(int $limit): self
+    {
+        $this->limit = $limit;
+        return $this;
+    }
+
+    /**
+     * Batch process returning the index for query.
+     * @param callable $callback
+     * @return void
+     */
+    public function process(callable $callback): void
+    {
+        for ($batch = 1; $this->start < $this->size; $batch++) {
+            $callback($this->start, $this->limit);
+            $this->start = $batch * $this->limit;
+        }
+    }
+}