Release 0.9.0-beta20

luposlip · Jan 6, 2025 · 2b59b79 · 2b59b79
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -7,6 +7,14 @@ All notable changes to this project will be documented in this file. This change
 - Timestamps for historical versions
 - Optimize (speed+size of) low level index format
 
+## [0.9.0-beta20] - 2025-01-06
+
+"Happy New Year"-release!
+
+### Enhanced
+
+- Throwing a sane error, when opening an EMPTY database!
+
 ## [0.9.0-beta19] - 2024-10-25
 
 Support `nippy` based files in a `zip` based database - called `zippy`

diff --git a/README.md b/README.md
@@ -3,7 +3,7 @@
 # nd-db
 
 ```clojure
-[com.luposlip/nd-db "0.9.0-beta19"]
+[com.luposlip/nd-db "0.9.0-beta20"]
 ```
 
 _Newline Delimited (read-only) Databases!_

diff --git a/project.clj b/project.clj
@@ -1,4 +1,4 @@
-(defproject com.luposlip/nd-db "0.9.0-beta19"
+(defproject com.luposlip/nd-db "0.9.0-beta20"
   :description "Clojure library to use newline delimited files as fast read-only databases."
   :url "https://github.com/luposlip/nd-db"
   :license {:name "Apache License, Version 2.0"

diff --git a/resources/test/empty.ndnippy b/resources/test/empty.ndnippy
diff --git a/src/nd_db/index.clj b/src/nd_db/index.clj
@@ -52,30 +52,34 @@
     ;; without parallelization: 18s
     ;; with: 6s (partition size 2048, fold size 32
     ;; that's around 2/3 less processing time
-    (let [[fline & rlines] (line-seq rdr)
-          [lines init-offset] (if skip-first?
-                                [rlines (inc (count (.getBytes ^String fline)))]
-                                [(cons fline rlines) 0])]
-      (with-meta
-        (->> lines
-             (partition-all 2048)
-             (reduce
-              (fn [[offset _ :as acc] part]
-                (let [res (->> part
-                               (into [])
-                               (r/fold 32
-                                       idx-combinr
-                                       (idx-reducr id-fn)))
-                      [s l] (->> res peek rest)]
-                  (-> acc
-                      (update 0 #(+ 1 % s l))
-                      (update 1 merge (reduce
-                                       (fn [a [id s l]]
-                                         (assoc a id [(+ offset s) l]))
-                                       {} res)))))
-              [init-offset {}])
-             second)
-        {:as-of (Instant/now)}))))
+    (let [[fline & rlines :as all-lines] (line-seq rdr)          ]
+      (if all-lines
+        (let [[lines init-offset] (if skip-first?
+                                    [rlines (inc (count (.getBytes ^String fline)))]
+                                    [(cons fline rlines) 0])]
+            (with-meta
+              (->> lines
+                   (partition-all 2048)
+                   (reduce
+                    (fn [[offset _ :as acc] part]
+                      (let [res (->> part
+                                     (into [])
+                                     (r/fold 32
+                                             idx-combinr
+                                             (idx-reducr id-fn)))
+                            [s l] (->> res peek rest)]
+                        (-> acc
+                            (update 0 #(+ 1 % s l))
+                            (update 1 merge (reduce
+                                             (fn [a [id s l]]
+                                               (assoc a id [(+ offset s) l]))
+                                             {} res)))))
+                    [init-offset {}])
+                   second)
+              {:as-of (Instant/now)}))
+        (throw (ex-info "Cannot use empty database!" {:filename filename
+                                                      :id-fn? (ifn? id-fn)
+                                                      :skip-first? skip-first?}))))))
 
 (defn reader
   "Returns a BufferedReader of the database index.

diff --git a/test/nd_db/index_test.clj b/test/nd_db/index_test.clj
@@ -4,7 +4,8 @@
             [nd-db
              [core :as nddb]
              [index :as sut]]
-            [nd-db.util :as ndut]))
+            [nd-db.util :as ndut])
+  (:import clojure.lang.ExceptionInfo))
 
 (def by-id #(Integer. ^String (second (re-find #"^\{\"id\":(\d+)" %))))
 
@@ -50,3 +51,9 @@
         new-index-keys (-> new-db :index deref keys set)]
     (is (ndut/db? new-db))
     (is (= new-id (new-index-keys new-id)))))
+
+(deftest empty-db
+  (is (thrown?
+       ExceptionInfo
+       (nddb/db :filename "resources/test/empty.ndnippy"
+                :id-path :id))))