Update InternalVersionT::zero in addWrite call

There can be other conflict sets in the same thread

Bench.cpp

@@ -358,21 +358,6 @@ void benchWorstCaseForRadixRangeRead() {
   // }
 }
 
-void benchMetrics() {
-  ankerl::nanobench::Bench bench;
-  ConflictSet cs{0};
-
-  int count;
-  ConflictSet::MetricsV1 *m;
-  cs.getMetricsV1(&m, &count);
-  bench.batch(count);
-  bench.run("fetch metric", [&]() {
-    for (int i = 0; i < count; ++i) {
-      m[i].getValue();
-    }
-  });
-}
-
 void benchCreateAndDestroy() {
   ankerl::nanobench::Bench bench;
 
@@ -382,6 +367,5 @@ void benchCreateAndDestroy() {
 int main(void) {
   benchConflictSet();
   benchWorstCaseForRadixRangeRead();
-  benchMetrics();
   benchCreateAndDestroy();
 }

ConflictSet.cpp

@@ -1111,7 +1111,8 @@ Node *&getOrCreateChild(Node *&self, uint8_t index, WriteContext *tls) {
       memmove(self16->index + i + 1, self16->index + i,
               self->numChildren - (i + 1));
       memmove(self16->children + i + 1, self16->children + i,
-              (self->numChildren - (i + 1)) * sizeof(self16->children[0]));
+              (self->numChildren - (i + 1)) *
+                  sizeof(self16->children[0])); // NOLINT
       memmove(self16->childMaxVersion + i + 1, self16->childMaxVersion + i,
               (self->numChildren - (i + 1)) *
                   sizeof(self16->childMaxVersion[0]));
@@ -3176,6 +3177,11 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
   }
 
   void addWrites(const WriteRange *writes, int count, int64_t writeVersion) {
+    // There could be other conflict sets in the same thread. We need
+    // InternalVersionT::zero to be correct for this conflict set for the
+    // lifetime of the current call frame.
+    InternalVersionT::zero = oldestVersion;
+
     assert(writeVersion >= newestVersionFullPrecision);
 
     if (writeVersion > newestVersionFullPrecision + kNominalVersionWindow) {

HashTable.cpp

@@ -98,6 +98,13 @@ void ConflictSet::setOldestVersion(int64_t oldestVersion) {
 
 int64_t ConflictSet::getBytes() const { return -1; }
 
+void ConflictSet::getMetricsV1(MetricsV1 **metrics, int *count) const {
+  *metrics = nullptr;
+  *count = 0;
+}
+
+double ConflictSet::MetricsV1::getValue() const { return 0; }
+
 ConflictSet::ConflictSet(int64_t oldestVersion)
     : impl(new(safe_malloc(sizeof(Impl))) Impl{oldestVersion}) {}
 

test_conflict_set.py

@@ -56,6 +56,20 @@ def test_conflict_set():
         assert cs.check(read(0, key), read(1, key)) == [Result.TOO_OLD, Result.COMMIT]
 
 
+def test_update_zero():
+    with DebugConflictSet() as cs1:
+        with DebugConflictSet() as cs2:
+            cs1.addWrites(2, write(b""))
+            cs1.setOldestVersion(2)
+            # "zero" is now 2
+
+            # make a Node48
+            for i in range(256 - 17, 256):
+                cs2.addWrites(int(1), write(bytes([i])))
+            # Scan until first point write
+            cs2.check(read(0, b"\x00", bytes([256 - 17])))
+
+
 def test_inner_full_words():
     with DebugConflictSet() as cs:
         cs.addWrites(1, write(b"\x3f\x61"), write(b"\x81\x61"))