Support for erasing records from the log

git-svn-id: https://babudb.googlecode.com/svn/trunk@359 d4c7dd96-b7b2-11dd-893d-d98698f66bbf

Author: fhupfeld

cpp/TODO

@@ -9,3 +9,6 @@
 
 == LogIndex
 - Put keys in tree nodes (better cache locality)
+
+== Log
+- remove LSN support in the log (should be done at user-level)

cpp/include/babudb/log/log_iterator.h

@@ -30,11 +30,21 @@ class LogIterator {
 
   Buffer& operator * () const;
   Buffer* operator -> () const;
-  Buffer asData() const { return this->operator *(); }
+  Buffer asData() const {
+    return this->operator *();
+  }
   Buffer getOperationWithFrame() const;
 
   record_type_t getType() const;
-  lsn_t GetLSN() const { return lsn; };
+  lsn_t GetLSN() const {
+    return lsn; 
+  }
+  RecordIterator getCurrentRecord() const {
+    return current_record;
+  }
+  LogSectionIterator getCurrentSection() const {
+    return current_section;
+  }
 
   static RecordIterator section_begin(const LogSectionIterator& section);
   static RecordIterator section_end(const LogSectionIterator& section);

cpp/include/babudb/log/log_section.h

@@ -50,6 +50,10 @@ class LogSection : public SequentialFile {
   // Commit an empty transaction with a new LSN
   void SeekForwardTo(babudb::lsn_t);
 
+  // Erase record pointed to by iterator. Iterator becomes
+  // valid again after increment or decrement.
+  void Erase(SequentialFile::iterator it);
+
 private:
 	bool in_transaction;
 	lsn_t first_lsn; // the first lsn in this file

cpp/include/babudb/log/record_iterator.h

@@ -48,6 +48,9 @@ class RecordIterator
 	}
 
 	void reverse();
+  bool isForwardIterator() const {
+    return is_forward_iterator;
+  }
 
 	bool operator != ( const RecordIterator& other ) const;
 	bool operator == ( const RecordIterator& other ) const;

cpp/src/log/log_iterator_test.cpp

@@ -146,3 +146,55 @@ TEST_TMPDIR(LogIterator,babudb)
     log.close();
   }
 }
+
+TEST_TMPDIR(LogIteratorAndErase,babudb)
+{
+  Log log(testPath("testlog"));
+  LogSection* tail = log.getTail();
+  
+  tail->Append(DummyOperation('A')); tail->Commit();
+  tail->Append(DummyOperation('B')); tail->Commit();
+  tail->Append(DummyOperation('C')); tail->Commit();
+  
+  DummyOperation op(0);
+  Log::iterator i = log.begin();
+  ++i;
+  EXPECT_TRUE(op.Deserialize(*i).value == 'B');
+  EXPECT_TRUE(i.GetLSN() == 2);
+
+  tail->Erase(i.getCurrentRecord());
+  
+  ++i;
+  EXPECT_TRUE(op.Deserialize(*i).value == 'C');
+  EXPECT_TRUE(i.GetLSN() == 3);
+
+  --i;
+  EXPECT_TRUE(op.Deserialize(*i).value == 'A');
+  
+  log.close();
+}
+
+TEST_TMPDIR(LogIteratorAndEraseReverse,babudb)
+{
+  Log log(testPath("testlog"));
+  LogSection* tail = log.getTail();
+  
+  tail->Append(DummyOperation('A')); tail->Commit();
+  tail->Append(DummyOperation('B')); tail->Commit();
+  tail->Append(DummyOperation('C')); tail->Commit();
+  
+  DummyOperation op(0);
+  Log::iterator i = log.rbegin();
+  ++i;
+  EXPECT_TRUE(op.Deserialize(*i).value == 'B');
+
+  tail->Erase(i.getCurrentRecord());
+  
+  ++i;
+  EXPECT_TRUE(op.Deserialize(*i).value == 'A');
+
+  --i;
+  EXPECT_TRUE(op.Deserialize(*i).value == 'C');
+  
+  log.close();
+}

cpp/src/log/log_section.cpp

@@ -73,6 +73,18 @@ void LogSection::SeekForwardTo(babudb::lsn_t new_lsn) {
   Commit();
 }
 
+void LogSection::Erase(SequentialFile::iterator it) {
+  ASSERT_TRUE(it.getType() != LSN_RECORD_TYPE);
+  erase(record2offset(it.getRecord()));
+  // TODO: support erase of multi-record transactions
+  if (!it.isForwardIterator()) {
+    it.reverse();
+  }
+  --it;
+  ASSERT_TRUE(it.getType() == LSN_RECORD_TYPE);
+  erase(record2offset(it.getRecord()));
+}
+
 
 LogSectionIterator::LogSectionIterator(std::vector<LogSection*>& sections)
   : sections(sections) {}