non-iterative single-query restore-document for pgstorage

resources/sql/_ds_postgres.sql

@@ -44,3 +44,31 @@ INSERT INTO :i:repository-table
 -- :name get-last-document-frame :? :1
 -- :doc retrieve the last document-frame given the document-id.
 SELECT * FROM :i:repository-table WHERE document_id = :document-id order by "version" desc limit 1
+
+
+
+-- :name select-relevant-document-frames :? :*
+-- :doc retrieve all necessary document frames to restore the latest document version
+with RECURSIVE rec AS (
+  SELECT ru.*, 0 AS degree
+	  FROM :i:repository-table ru, (select rr.id from :i:repository-table rr where document_id = :document-id
+                                   order by version desc limit 1) as init
+   WHERE ru.id  = init.id
+   UNION
+  SELECT ru.*, rec.degree + 1 AS degree
+    FROM :i:repository-table ru
+         JOIN rec ON ru.id = rec.reference and rec.data_type != 'key')
+select * from rec;
+
+-- :name select-relevant-document-frames-by-version :? :*
+-- :doc retrieve all necessary document frames to restore a given document version
+with RECURSIVE rec AS (
+  SELECT ru.*, 0 AS degree
+	  FROM :i:repository-table ru, (select rr.id from :i:repository-table rr where document_id = :document-id
+                                                                             AND version = :version) as init
+   WHERE ru.id  = init.id
+   UNION
+  SELECT ru.*, rec.degree + 1 AS degree
+    FROM :i:repository-table ru
+         JOIN rec ON ru.id = rec.reference and rec.data_type != 'key')
+select * from rec;

src/document_storage/postgres/documents.clj

 (ns document-storage.postgres.documents
   (:require [document-storage.postgres.encoding :as encoding]
-            [editscript.core :as escript]))
+            [editscript.core :as escript]
+            [clj-helper.vector :as vhelper]))
 
 
 (defn get-document-frame-by-version [storage document-id version repository]
@@ -25,27 +26,34 @@
     (:version frame)))
 
 
-(defn restore-document [storage frame-id repository]
-  (when-let [frame (get-document-frame-by-id storage frame-id repository)]
-    (case (name (:data_type frame))
-      "key" (encoding/decode-document (:data frame))
-      "diff" (let [data (encoding/decode-document (:data frame))]
-               (escript/patch
-                       ;;;FIXME load document-frame by ID
-                (restore-document storage (:reference frame) repository)
-                (escript/edits->script data)))
-      (throw
-       (ex-info (str "Unknown data-type " (:data_type frame) " for frame " frame-id)
-                {:frame-id frame-id
-                 :frame frame})))))
+(defn restore-document-version [storage document-id version repository]
+  (when-let [frames (.run-query storage :select-relevant-document-frames-by-version
+                                {:repository repository
+                                 :document-id document-id
+                                 :version version})]
+    (let [next-frames (into {} (map (juxt :reference identity)) frames)
+          keyframe (vhelper/get-by frames (comp name :data_type) "key")]
+      (if keyframe
+        (loop [active-frame keyframe
+               data (encoding/decode-document (:data active-frame))]
+          (let [next-frame (get next-frames (:id active-frame))]
+            (if-not next-frame
+              data
+              (recur next-frame (escript/patch
+                                 data
+                                 (escript/edits->script (encoding/decode-document (:data next-frame))))))))
+        (throw
+         (ex-info (str "No keyframe for document " document-id " with version " version " in repository " repository)
+                  {:document-id document-id
+                   :version version
+                   :repository repository}))))))
 
 (defn load-document
   ([storage document-id repository]
    (when-let [last-document-version (get-last-document-version storage document-id repository)]
      (load-document storage document-id last-document-version repository)))
   ([storage document-id version repository]
-   (when-let [frame (get-document-frame-by-version storage document-id version repository)]
-     (restore-document storage (:id frame) repository))))
+   (restore-document-version storage document-id version repository)))
 
 (defn save-keyframe [storage document-id document last-version repository]
   (let [doc (encoding/encode-document document)