Adds checks before setting SAVE_PARTITION to 0, a=chris

diff --git a/src/executables/QueueServer.php b/src/executables/QueueServer.php
index 84ff05e4a..36b62c05c 100644
--- a/src/executables/QueueServer.php
+++ b/src/executables/QueueServer.php
@@ -1762,8 +1762,16 @@ class QueueServer implements CrawlConstants
             IndexDocumentBundle::NEXT_PARTITION_FILE;
         $next_partition_to_add = (file_exists($next_partition_file)) ?
             intval(file_get_contents($next_partition_file)) : 0;
-        $save_partition = $this->index_archive->documents->parameters[
-            "SAVE_PARTITION"] ?? 0;
+        $documents = $this->index_archive->documents;
+        $save_partition = $documents->parameters["SAVE_PARTITION"] ?? 0;
+        if ($save_partition == 0) { //double check
+            $documents = $this->index_archive->documents;
+            // this will read and if 0 recompute using a glob
+            $documents_parameters =
+                $this->index_archive->documents->getParameterInfo(
+                    $documents->folder);
+            $save_partition = $documents_parameters['SAVE_PARTITION'] ?? 0;
+        }
         L\crawlLog("Advance check details: Last:" .
             $this->last_next_partition_to_add . " Next:" .
             $next_partition_to_add . " Save:" . $save_partition);
diff --git a/src/library/PartitionDocumentBundle.php b/src/library/PartitionDocumentBundle.php
index 598d950c4..5ae09c11f 100644
--- a/src/library/PartitionDocumentBundle.php
+++ b/src/library/PartitionDocumentBundle.php
@@ -603,6 +603,9 @@ class PartitionDocumentBundle
     }
     /**
      * Save the operating parameters of this PartitionDocumentBundle
+     * @param bool $force saveParameter() does a sanity check before
+     *   writing either an empty parameter file or writing a SAVE_PARTITION
+     *   with value 0. If $force is true, this check is skipped.
      */
     public function saveParameters()
     {
@@ -631,6 +634,11 @@ class PartitionDocumentBundle
                 $parameters["RECORD_COMPRESSOR"] ??= $parameters["COMPRESSOR"];
                 $parameters["BLOB_COMPRESSOR"] ??= $parameters["COMPRESSOR"];
             }
+            if (empty($parameters['SAVE_PARTITION']) ||
+                $parameters['SAVE_PARTITION'] == 0) {
+                $parameters['SAVE_PARTITION'] =
+                    max(count(glob("$folder/*" . self::INDEX_EXTENSION))-1, 0);
+            }
             return $parameters;
         } else {
             return [];