Small tweaks and bugfixes for Issue 18 and 19.

Slight tweak to the no-overlap optimization: only push to
level 2 to reduce the amount of wasted space when the same
small key range is being repeatedly overwritten.

Fix for Issue 18: Avoid failure on Windows by avoiding
deletion of lock file until the end of DestroyDB().

Fix for Issue 19: Disregard sequence numbers when checking for 
overlap in sstable ranges. This fixes issue 19: when writing 
the same key over and over again, we would generate a sequence 
of sstables that were never merged together since their sequence
numbers were disjoint.

Don't ignore map/unmap error checks.

Miscellaneous fixes for small problems Sanjay found while diagnosing
issue/9 and issue/16 (corruption_testr failures).
- log::Reader reports the record type when it finds an unexpected type.
- log::Reader no longer reports an error when it encounters an expected
  zero record regardless of the setting of the "checksum" flag.
- Added a missing forward declaration.
- Documented a side-effects of larger write buffer sizes
  (longer recovery time).



git-svn-id: https://leveldb.googlecode.com/svn/trunk@37 62dab493-f737-651d-591e-8d6aee1b9529

1 files changed, 12 insertions, 7 deletions

diff --git a/db/version_set.cc b/db/version_set.cc
index 54342e4..816f189 100644
--- a/db/version_set.cc
+++ b/db/version_set.cc
@@ -99,11 +99,14 @@ int FindFile(const InternalKeyComparator& icmp,
 bool SomeFileOverlapsRange(
     const InternalKeyComparator& icmp,
     const std::vector<FileMetaData*>& files,
-    const InternalKey& smallest,
-    const InternalKey& largest) {
-  const int index = FindFile(icmp, files, smallest.Encode());
+    const Slice& smallest_user_key,
+    const Slice& largest_user_key) {
+  // Find the earliest possible internal key for smallest_user_key
+  InternalKey small(smallest_user_key, kMaxSequenceNumber, kValueTypeForSeek);
+  const int index = FindFile(icmp, files, small.Encode());
   return ((index < files.size()) &&
-          icmp.Compare(largest, files[index]->smallest) >= 0);
+          icmp.user_comparator()->Compare(
+              largest_user_key, files[index]->smallest.user_key()) >= 0);
 }
 
 // An internal iterator.  For a given version/level pair, yields
@@ -353,9 +356,11 @@ void Version::Unref() {
 }
 
 bool Version::OverlapInLevel(int level,
-                             const InternalKey& smallest,
-                             const InternalKey& largest) {
-  return SomeFileOverlapsRange(vset_->icmp_, files_[level], smallest, largest);
+                             const Slice& smallest_user_key,
+                             const Slice& largest_user_key) {
+  return SomeFileOverlapsRange(vset_->icmp_, files_[level],
+                               smallest_user_key,
+                               largest_user_key);
 }
 
 std::string Version::DebugString() const {