From 967cabcaf2428e725fe4bca2c2669dcf2dc2a147 Mon Sep 17 00:00:00 2001
From: Tomasz Grabiec <tgrabiec@scylladb.com>
Date: Thu, 21 Sep 2017 12:10:42 +0200
Subject: [PATCH] mvcc: Make the null state of partition_snapshot::change_mark
 explicit

---
 partition_version.hh | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/partition_version.hh b/partition_version.hh
index 92ab4370a2..dae916e802 100644
--- a/partition_version.hh
+++ b/partition_version.hh
@@ -196,6 +196,8 @@ public:
     // References and iterators into versions owned by the snapshot
     // obtained between two equal change_mark objects were produced
     // by that snapshot are guaranteed to be still valid.
+    //
+    // Has a null state which is != than anything returned by get_change_mark().
     class change_mark {
         uint64_t _reclaim_count = 0;
         size_t _versions_count = 0; // merge_partition_versions() removes versions on merge
@@ -211,6 +213,9 @@ public:
         bool operator!=(const change_mark& m) const {
             return !(*this == m);
         }
+        explicit operator bool() const {
+            return _reclaim_count > 0;
+        }
     };
 private:
     schema_ptr _schema;