Add prefix queries to bench

Bench.cpp

@@ -2,6 +2,7 @@
 #include "Internal.h"
 #include <byteswap.h>
 #include <cstdint>
+#include <cstring>
 
 #define ANKERL_NANOBENCH_IMPLEMENT
 #include "third_party/nanobench.h"
@@ -598,6 +599,24 @@ private:
   SkipList skipList;
 };
 
+ConflictSet::ReadRange prefixRange(Arena &arena, std::span<const uint8_t> key) {
+  int index;
+  for (index = key.size() - 1; index >= 0; index--)
+    if ((key[index]) != 255)
+      break;
+
+  // Must not be called with a string that consists only of zero or more '\xff'
+  // bytes.
+  if (index < 0) {
+    assert(false);
+  }
+
+  auto r = std::span<uint8_t>(new (arena) uint8_t[index + 1], index + 1);
+  memcpy(r.data(), key.data(), index + 1);
+  r[r.size() - 1]++;
+  return {key.data(), int(key.size()), r.data(), int(r.size())};
+}
+
 } // namespace
 
 constexpr int kNumKeys = 1000000;
@@ -606,19 +625,13 @@ constexpr int kOpsPerTx = 100;
 
 constexpr int kPrefixLen = 0;
 
-std::span<const uint8_t> makeKey(Arena &arena, int64_t index) {
+std::span<const uint8_t> makeKey(Arena &arena, int index) {
 
-  // auto result =
-  //     std::span<uint8_t>{new (arena) uint8_t[4 + kPrefixLen], 4 +
-  //     kPrefixLen};
-  // index = __builtin_bswap32(index);
-  // memset(result.data(), 0, kPrefixLen);
-  // memcpy(result.data() + kPrefixLen, &index, 4);
-
-  auto result = std::span<uint8_t>{new (arena) uint8_t[64], 64};
-  for (int i = 0; i < 64; ++i) {
-    result[i] = index & (1 << (64 - 1 - i)) ? '1' : '0';
-  }
+  auto result =
+      std::span<uint8_t>{new (arena) uint8_t[4 + kPrefixLen], 4 + kPrefixLen};
+  index = __builtin_bswap32(index);
+  memset(result.data(), 0, kPrefixLen);
+  memcpy(result.data() + kPrefixLen, &index, 4);
 
   return result;
 }
@@ -628,6 +641,7 @@ template <class ConflictSet_> void benchConflictSet(const std::string &name) {
   ConflictSet_ cs{0};
 
   bench.batch(kOpsPerTx);
+  bench.minEpochIterations(2000);
 
   int64_t version = 0;
 
@@ -702,6 +716,22 @@ template <class ConflictSet_> void benchConflictSet(const std::string &name) {
               [&]() { cs.check(reads.data(), results, kOpsPerTx); });
   }
 
+  {
+    std::vector<ConflictSet::ReadRange> reads;
+    auto iter = points.begin();
+    for (int i = 0; i < kOpsPerTx; ++i) {
+      auto r = prefixRange(arena, *iter);
+      r.readVersion = version - 1;
+      reads.push_back(r);
+      ++iter;
+    }
+
+    auto *results = new (arena) ConflictSet::Result[kOpsPerTx];
+
+    bench.run(name + " (prefix reads)",
+              [&]() { cs.check(reads.data(), results, kOpsPerTx); });
+  }
+
   {
     std::vector<ConflictSet::ReadRange> reads;
     auto iter = points.begin();
@@ -744,6 +774,29 @@ template <class ConflictSet_> void benchConflictSet(const std::string &name) {
     });
   }
 
+  {
+    std::vector<ConflictSet::WriteRange> writes;
+    auto iter = points.begin();
+    for (int i = 0; i < kOpsPerTx; ++i) {
+      ConflictSet::WriteRange w;
+      auto r = prefixRange(arena, *iter);
+      w.begin.p = r.begin.p;
+      w.begin.len = r.begin.len;
+      w.end.p = r.end.p;
+      w.end.len = r.end.len;
+      writes.push_back(w);
+      ++iter;
+    }
+
+    bench.run(name + " (prefix writes)", [&]() {
+      auto v = ++version;
+      for (auto &w : writes) {
+        w.writeVersion = v;
+      }
+      cs.addWrites(writes.data(), writes.size());
+    });
+  }
+
   {
     std::vector<ConflictSet::WriteRange> writes;
     auto iter = points.begin();