diff --git a/backend/src/app/srepl/helpers.clj b/backend/src/app/srepl/helpers.clj
index 307ccbc54..ecb25981d 100644
--- a/backend/src/app/srepl/helpers.clj
+++ b/backend/src/app/srepl/helpers.clj
@@ -25,6 +25,7 @@
    [app.util.blob :as blob]
    [app.util.time :as dt]
    [clojure.spec.alpha :as s]
+   [clojure.stacktrace :as strace]
    [clojure.walk :as walk]
    [cuerdas.core :as str]
    [expound.alpha :as expound]))
@@ -78,7 +79,7 @@
       (update file :data blob/decode))))
 
 (def ^:private sql:retrieve-files-chunk
-  "SELECT id, name, modified_at, data FROM file
+  "SELECT id, name, created_at, data FROM file
     WHERE created_at < ? AND deleted_at is NULL
     ORDER BY created_at desc LIMIT ?")
 
@@ -88,26 +89,39 @@
 
   The `on-file` parameter should be a function that receives the file
   and the previous state and returns the new state."
-  [system & {:keys [chunk-size on-file] :or {chunk-size 10}}]
+  [system & {:keys [chunk-size max-chunks start-at on-file on-error on-end]
+             :or {chunk-size 10 max-chunks Long/MAX_VALUE}}]
   (letfn [(get-chunk [conn cursor]
             (let [rows (db/exec! conn [sql:retrieve-files-chunk cursor chunk-size])]
               [(some->> rows peek :created-at) (seq rows)]))
 
           (get-candidates [conn]
             (->> (d/iteration (partial get-chunk conn)
-                                       :vf second
-                                       :kf first
-                                       :initk (dt/now))
-                 (sequence cat)
-                 (map #(update % :data blob/decode))))]
+                              :vf second
+                              :kf first
+                              :initk (or start-at (dt/now)))
+                 (take max-chunks)
+                 (mapcat identity)
+                 (map #(update % :data blob/decode))))
+
+          (on-error* [file cause]
+            (println "unexpected exception happened on processing file: " (:id file))
+            (strace/print-stack-trace cause))]
 
     (db/with-atomic [conn (:app.db/pool system)]
       (loop [state {}
              files (get-candidates conn)]
         (if-let [file (first files)]
-          (let [state (on-file file state)]
-            (recur state (rest files)))
-          state)))))
+          (let [state' (try
+                         (on-file file state)
+                         (catch Throwable cause
+                           (let [on-error (or on-error on-error*)]
+                             (on-error file cause))))]
+            (recur (or state' state) (rest files)))
+
+          (if (fn? on-end)
+            (on-end state)
+            state))))))
 
 
 (defn analyze-file-data