🐛 Fix list-column CSV ingest and serialize graph session access

COPY failed on any file with container shapes: list-typed DDL columns (shapes UUID[], points STRING[], strokes JSON[], ...) were JSON-encoded in staging CSVs, which Ladybug's list parser rejects. Write Kuzu list literals instead, typed per column. Also: value->clj no longer crashes on LIST/STRUCT values (binding lacks value_get_value support; fall back to string), and the debug session Connection is now guarded by a per-session lock — it was shared unsynchronized between the msgbus sync loop and HTTP query/export handlers, and one lost DETACH DELETE was observed under concurrent refetch load.

Signed-off-by: Álvaro Tejero Cantero <alvorithm@teje.ro>

backend/src/app/graph/bulk.clj

@@ -51,6 +51,43 @@
     (coll? v)     (csv-escape-string (json/encode v))
     :else         (csv-escape-string (str v))))
 
+(defn- kuzu-list-element
+  "Format one element of a Ladybug LIST column for CSV COPY. Kuzu parses
+  the (CSV-unquoted) field as a list literal: bare values for UUID/number
+  elements, single-quoted strings (backslash-escaped) for STRING/JSON."
+  [elem-type v]
+  (cond
+    (nil? v)
+    "NULL"
+
+    (contains? #{"STRING" "JSON"} elem-type)
+    (let [s (if (coll? v) (json/encode v) (csv-normalize-string (str v)))]
+      (str "'" (-> s
+                   (str/replace "\\" "\\\\")
+                   (str/replace "'" "\\'"))
+           "'"))
+
+    :else
+    (str v)))
+
+(defn- kuzu-list-cell
+  "CSV cell for a LIST-typed column (`UUID[]`, `STRING[]`, `JSON[]`, …).
+  JSON-encoding the collection (as `csv-cell` does) is wrong here: Kuzu
+  expects its own list literal, e.g. `[id1,id2]` with bare elements."
+  [ladybug-type v]
+  (let [elem-type (subs ladybug-type 0 (- (count ladybug-type) 2))
+        elems     (if (coll? v) (seq v) [v])]
+    (csv-escape-string
+     (str "[" (str/join "," (map #(kuzu-list-element elem-type %) elems)) "]"))))
+
+(defn- csv-typed-cell
+  [ladybug-type v]
+  (if (and (some? v)
+           (string? ladybug-type)
+           (str/ends-with? ladybug-type "[]"))
+    (kuzu-list-cell ladybug-type v)
+    (csv-cell v)))
+
 (defn- cypher-file-path
   [^File file]
   (-> (.getAbsolutePath file)
@@ -59,11 +96,13 @@
 
 (defn- write-node-csv!
   [^File file table rows]
-  (let [columns (nodes/column-keys table)]
+  (let [columns (nodes/column-keys table)
+        types   (mapv #(nodes/column-ladybug-type table %) columns)]
     (with-open [w (io/writer file :encoding "UTF-8")]
       (.write w (str (str/join "," (map name columns)) "\n"))
       (doseq [row rows]
-        (.write w (str (str/join "," (map #(csv-cell (get row %)) columns))
+        (.write w (str (str/join "," (map (fn [k t] (csv-typed-cell t (get row k)))
+                                          columns types))
                        "\n"))))))
 
 (defn- write-edge-csv!

backend/src/app/graph/debug.clj

@@ -66,8 +66,9 @@
     (some-> (get @sessions (session-key profile-id))
             (as-> current
                   (when (= file-id (:file-id current))
-                    (let [result (graph.sync/apply-changes!
-                                  conn (:index current) changes revn)
+                    (let [result (locking (:lock current)
+                                   (graph.sync/apply-changes!
+                                    conn (:index current) changes revn))
                           sync-at (ct/now)]
                       (swap! sessions assoc-in [(session-key profile-id) :index]
                              (:index result))
@@ -152,8 +153,12 @@
                                                       :skip-validation? true)
             index (graph.sync/build-index file-id (:revn meta) (:projection meta))
             session
+            ;; :lock serializes access to the shared Connection between the
+            ;; msgbus sync loop (writes) and HTTP handlers (reads); the Java
+            ;; binding gives no thread-safety guarantee for one Connection.
             (-> {:db db
                  :conn conn
+                 :lock (Object.)
                  :file-id file-id
                  :meta meta
                  :index index
@@ -174,9 +179,10 @@
     (ex/raise :type :validation
               :code :missing-query
               :hint "cypher query is required"))
-  (if-let [{:keys [conn]} (get @sessions (session-key profile-id))]
-    (-> (ladybug/query-on-connection! conn statement)
-        format-query-result)
+  (if-let [{:keys [conn lock]} (get @sessions (session-key profile-id))]
+    (locking (or lock ::no-lock)
+      (-> (ladybug/query-on-connection! conn statement)
+          format-query-result))
     (ex/raise :type :not-found
               :code :graph-session-not-loaded
               :hint "load a file graph before running queries")))
@@ -220,14 +226,15 @@
   loaded. Queries the Ladybug database (not the sync index) so the view
   reflects actual DB state, including drift."
   [profile-id]
-  (when-let [{:keys [conn file-id index]} (get @sessions (session-key profile-id))]
-    (let [{:keys [nodes] nodes-truncated? :truncated?} (export-nodes conn)
-          {:keys [edges] edges-truncated? :truncated?} (export-edges conn)]
-      {:file-id   (str file-id)
-       :revn      (:revn index)
-       :truncated (boolean (or nodes-truncated? edges-truncated?))
-       :nodes     nodes
-       :edges     edges})))
+  (when-let [{:keys [conn lock file-id index]} (get @sessions (session-key profile-id))]
+    (locking (or lock ::no-lock)
+      (let [{:keys [nodes] nodes-truncated? :truncated?} (export-nodes conn)
+            {:keys [edges] edges-truncated? :truncated?} (export-edges conn)]
+        {:file-id   (str file-id)
+         :revn      (:revn index)
+         :truncated (boolean (or nodes-truncated? edges-truncated?))
+         :nodes     nodes
+         :edges     edges}))))
 
 (defn console-context
   "Build template data for the graph debug console page."

backend/src/app/graph/ladybug.clj

@@ -97,7 +97,13 @@
 (defn- value->clj
   [^Value value]
   (when-not (.isNull value)
-    (let [v (.getValue value)]
+    (let [v (try
+              (.getValue value)
+              (catch Exception _
+                ;; LIST/STRUCT values are not supported by the binding's
+                ;; getValue (\"value_get_value\"); fall back to the textual
+                ;; representation so console queries do not crash.
+                (.toString value)))]
       (cond
         (instance? Long v)    v
         (instance? Integer v) (long v)