Move consumePartialKey, and allow empty partial key

ConflictSet.cpp

@@ -1125,6 +1125,53 @@ Node *getFirstChildExists(Node *self) {
   }
 }
 
+// Consume any partial key of `self`, and update `self` and
+// `key` such that `self` is along the search path of `key`
+void consumePartialKey(Node *&self, std::span<const uint8_t> &key,
+                       InternalVersionT writeVersion, WriteContext *tls) {
+  if (self->partialKeyLen == 0) {
+    return;
+  }
+  // Handle an existing partial key
+  int commonLen = std::min<int>(self->partialKeyLen, key.size());
+  int partialKeyIndex =
+      longestCommonPrefix(self->partialKey(), key.data(), commonLen);
+  if (partialKeyIndex < self->partialKeyLen) {
+    auto *old = self;
+    // Since root cannot have a partial key
+    assert(old->parent != nullptr);
+    InternalVersionT oldMaxVersion = exchangeMaxVersion(old, writeVersion);
+
+    // *self will have one child (old)
+    auto *newSelf = tls->allocate<Node3>(partialKeyIndex);
+
+    newSelf->parent = old->parent;
+    newSelf->parentsIndex = old->parentsIndex;
+    newSelf->partialKeyLen = partialKeyIndex;
+    newSelf->entryPresent = false;
+    newSelf->numChildren = 1;
+
+    memcpy(newSelf->partialKey(), old->partialKey(), newSelf->partialKeyLen);
+
+    uint8_t oldDistinguishingByte = old->partialKey()[partialKeyIndex];
+    old->parent = newSelf;
+    old->parentsIndex = oldDistinguishingByte;
+    newSelf->index[0] = oldDistinguishingByte;
+    newSelf->children[0] = old;
+    newSelf->childMaxVersion[0] = oldMaxVersion;
+    self = newSelf;
+
+    memmove(old->partialKey(), old->partialKey() + partialKeyIndex + 1,
+            old->partialKeyLen - (partialKeyIndex + 1));
+    old->partialKeyLen -= partialKeyIndex + 1;
+
+    // We would consider decreasing capacity here, but we can't invalidate
+    // old since it's not on the search path. setOldestVersion will clean it
+    // up.
+  }
+  key = key.subspan(partialKeyIndex, key.size() - partialKeyIndex);
+}
+
 // Caller is responsible for assigning a non-null pointer to the returned
 // reference if null. Updates child's max version to `newMaxVersion` if child
 // exists but does not have a partial key.
@@ -2743,51 +2790,6 @@ checkMaxBetweenExclusiveImpl<true>(Node *n, int begin, int end,
                                    InternalVersionT readVersion, ReadContext *);
 #endif
 
-// Consume the partial key of `self` (which must exist), and update `self` and
-// `key` such that `self` is along the search path of `key`
-void consumePartialKey(Node *&self, std::span<const uint8_t> &key,
-                       InternalVersionT writeVersion, WriteContext *tls) {
-  assert(self->partialKeyLen > 0);
-  // Handle an existing partial key
-  int commonLen = std::min<int>(self->partialKeyLen, key.size());
-  int partialKeyIndex =
-      longestCommonPrefix(self->partialKey(), key.data(), commonLen);
-  if (partialKeyIndex < self->partialKeyLen) {
-    auto *old = self;
-    // Since root cannot have a partial key
-    assert(old->parent != nullptr);
-    InternalVersionT oldMaxVersion = exchangeMaxVersion(old, writeVersion);
-
-    // *self will have one child (old)
-    auto *newSelf = tls->allocate<Node3>(partialKeyIndex);
-
-    newSelf->parent = old->parent;
-    newSelf->parentsIndex = old->parentsIndex;
-    newSelf->partialKeyLen = partialKeyIndex;
-    newSelf->entryPresent = false;
-    newSelf->numChildren = 1;
-
-    memcpy(newSelf->partialKey(), old->partialKey(), newSelf->partialKeyLen);
-
-    uint8_t oldDistinguishingByte = old->partialKey()[partialKeyIndex];
-    old->parent = newSelf;
-    old->parentsIndex = oldDistinguishingByte;
-    newSelf->index[0] = oldDistinguishingByte;
-    newSelf->children[0] = old;
-    newSelf->childMaxVersion[0] = oldMaxVersion;
-    self = newSelf;
-
-    memmove(old->partialKey(), old->partialKey() + partialKeyIndex + 1,
-            old->partialKeyLen - (partialKeyIndex + 1));
-    old->partialKeyLen -= partialKeyIndex + 1;
-
-    // We would consider decreasing capacity here, but we can't invalidate
-    // old since it's not on the search path. setOldestVersion will clean it
-    // up.
-  }
-  key = key.subspan(partialKeyIndex, key.size() - partialKeyIndex);
-}
-
 // Returns a pointer the pointer to the newly inserted node in the tree.  Caller
 // must set `entryPresent`, and `entry` fields.  All nodes along the search path
 // of the result will have `maxVersion` set to `writeVersion` as a
@@ -2814,11 +2816,9 @@ Node **insert(Node **self, std::span<const uint8_t> key,
 
     self = &child;
 
-    if ((*self)->partialKeyLen > 0) {
-      consumePartialKey(*self, key, writeVersion, tls);
-      assert(maxVersion(*self, impl) <= writeVersion);
-      setMaxVersion(*self, impl, writeVersion);
-    }
+    consumePartialKey(*self, key, writeVersion, tls);
+    assert(maxVersion(*self, impl) <= writeVersion);
+    setMaxVersion(*self, impl, writeVersion);
   }
 }