Squashed 'src/leveldb/' changes from aca1ffc..ae6c262

ae6c262 Merge branch 'leveldb' into ripple-fork
28fa222 Looks like a bit more delay is needed to smooth the latency.
a18f3e6 Tidy up JobQueue, add ripple_core module
ab82e57 Release leveldb 1.12
02c6259 Release leveldb 1.11
5bbb544 Rate limit compactions with a 25ms pause after each complete file.
8c29c47 LevelDB issue 178 fix: cannot resize a level 0 compaction set
18b245c Added GNU/kFreeBSD kernel name (TARGET_OS)
8be9d12 CondVar::SignalAll was broken, leading to deadlocks on Windows builds. http://code.google.com/p/leveldb/issues/detail?id=149
c9fc070 Upgrade LevelDB to 1.10.0, mostly for better write stall logging.
8215b15 Tweak to variable name to support unity build

git-subtree-dir: src/leveldb
git-subtree-split: ae6c2620b2ef3d5c69e63dc0eda865d6a39fa061

db/version_set.cc

@@ -1331,14 +1331,19 @@ Compaction* VersionSet::CompactRange(
   }
 
   // Avoid compacting too much in one shot in case the range is large.
-  const uint64_t limit = MaxFileSizeForLevel(level);
-  uint64_t total = 0;
-  for (size_t i = 0; i < inputs.size(); i++) {
-    uint64_t s = inputs[i]->file_size;
-    total += s;
-    if (total >= limit) {
-      inputs.resize(i + 1);
-      break;
+  // But we cannot do this for level-0 since level-0 files can overlap
+  // and we must not pick one file and drop another older file if the
+  // two files overlap.
+  if (level > 0) {
+    const uint64_t limit = MaxFileSizeForLevel(level);
+    uint64_t total = 0;
+    for (size_t i = 0; i < inputs.size(); i++) {
+      uint64_t s = inputs[i]->file_size;
+      total += s;
+      if (total >= limit) {
+        inputs.resize(i + 1);
+        break;
+      }
     }
   }