From f5ed1408c847be69ef1b3b1b452f8374ff581b0b Mon Sep 17 00:00:00 2001
From: dbushenko <d.bushenko@gmail.com>
Date: Fri, 13 Oct 2017 20:35:06 +0300
Subject: [PATCH 1/2] Added idempotent function codax.store/connection

---
 src/codax/store.clj | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/codax/store.clj b/src/codax/store.clj
index c205112..39e2c14 100644
--- a/src/codax/store.clj
+++ b/src/codax/store.clj
@@ -284,6 +284,11 @@
       (swap! open-databases assoc path db)
       db)))
 
+(defn connection [ path ]
+  (let [full-path (to-canonical-path-string path)
+        con (get @open-databases full-path)]
+      (or con (open-database path))))
+
 ;;;;; Transactions
 
 (defn- update-database! [{:keys [db root-id id-counter manifest]} nodes-offset manifest-delta nodes-by-address]

From 68d2d33af6759959f98c47398df0c2607324e922 Mon Sep 17 00:00:00 2001
From:  <d.bushenko@gmail.com>
Date: Sun, 1 Apr 2018 23:21:38 +0300
Subject: [PATCH 2/2] Introduced function next-id!

---
 src/codax/operations.clj | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/src/codax/operations.clj b/src/codax/operations.clj
index df80732..2b8022b 100644
--- a/src/codax/operations.clj
+++ b/src/codax/operations.clj
@@ -228,3 +228,31 @@
   (when (empty? path) (throw (ex-info "Invalid Path" {:cause :empty-path
                                                       :message "You cannot clear the empty (root) path."})))
   (clear-path tx path))
+
+
+;;;;;
+
+(defn next-id!
+  "Function generates auto incremented id starting from 0 for the specified entity.
+  Parameters:
+    db -- opened database
+    entity -- the entity for which the id should be generated.
+  Return:
+    The value of the next available id for the specified entity.
+  Usage examples:
+    (next-id! db :person) => 0
+    (-> db (next-id! :person)) => 1
+  "
+  [ db entity ]
+  (let [n (atom nil)]    
+    (c/with-write-transaction [db tx]
+      
+      ;; Read previous index value. If it is absent -- use 0 instead;
+      (reset! n (or (c/get-at! db [:codax/indicies entity]) 0))
+      
+      ;; Create or update the next index value with incremented previous value
+      (c/assoc-at tx [:codax/indicies entity] (inc @n)))
+
+    ;; Return original index value
+    @n))
+