Skip unversioned until non-adjacent mutation in facade

Only implemented for forward reads so far

Bench.cpp

@@ -103,7 +103,62 @@ void bulkFirstGeq() {
             [&] { versionedMap.firstGeq(keys, iterators, kNumQueries); });
 }
 
+void facadeVersionedOnlyRead() {
+  Facade facade{0};
+  constexpr int kNumKeys = 10000;
+  ankerl::nanobench::Bench bench;
+  bench.batch(kNumKeys);
+
+  const int64_t beginBytes = __builtin_bswap64(0);
+  const int64_t endBytes = __builtin_bswap64(kNumKeys);
+  const String begin{(const uint8_t *)&beginBytes, 8};
+  const String end{(const uint8_t *)&endBytes, 8};
+
+  // Insert clear in entire range, so that all reads are served from versioned,
+  // logically and hopefully physically.
+  {
+    weaselab::VersionedMap::Mutation mutations[] = {
+        {begin.data(), int(begin.size()), end.data(), int(end.size()),
+         weaselab::VersionedMap::Clear},
+    };
+    facade.addMutations(mutations, sizeof(mutations) / sizeof(mutations[0]),
+                        facade.getVersion() + 1);
+  }
+
+  // Add keys
+  for (int i = 0; i < kNumKeys; ++i) {
+    const int64_t k = __builtin_bswap64(i);
+    weaselab::VersionedMap::Mutation mutations[] = {
+        {(const uint8_t *)&k, 8, (const uint8_t *)&k, 8,
+         weaselab::VersionedMap::Set},
+    };
+    facade.addMutations(mutations, sizeof(mutations) / sizeof(mutations[0]),
+                        facade.getVersion() + 1);
+  }
+
+  // Populate the unversioned map
+  for (int i = 0; i < kNumKeys; ++i) {
+    const int64_t k = __builtin_bswap64(i);
+    weaselab::VersionedMap::Mutation mutations[] = {
+        {(const uint8_t *)&k, 8, (const uint8_t *)&k, 8,
+         weaselab::VersionedMap::Set},
+    };
+    facade.addMutations(mutations, sizeof(mutations) / sizeof(mutations[0]),
+                        facade.getVersion() + 1);
+  }
+  facade.setOldestVersion(facade.getVersion() - 1, /*force*/ true);
+
+  bench.run("Facade versioned-only read forward", [&]() {
+    facade.viewAt(facade.getVersion()).rangeRead(begin, end, kNumKeys, false);
+  });
+
+  bench.run("Facade versioned-only read reverse", [&]() {
+    facade.viewAt(facade.getVersion()).rangeRead(begin, end, kNumKeys, true);
+  });
+}
+
 int main() {
   monotonicallyIncreasing();
   bulkFirstGeq();
+  facadeVersionedOnlyRead();
 }