private CheckResult _lock_and_check_(KeyValuePair <TableKey, RecordAccessed> e)
{
Lockey lockey = Locks.Instance.Get(e.Key);
bool writeLock = e.Value.Dirty;
lockey.EnterLock(writeLock);
holdLocks.Add(lockey);
return(_check_(writeLock, e.Value));
}
private CheckResult _lock_and_check_()
{
if (savepoints.Count > 0)
{
// 全部 Rollback 时 Count 为 0；最后提交时 Count 必须为 1；其他情况属于Begin,Commit,Rollback不匹配。外面检查。
foreach (var log in savepoints[savepoints.Count - 1].Logs.Values)
{
if (log.Bean == null)
{
continue; // 特殊日志。不是 bean 的修改日志，当然也不会修改 Record。现在不会有这种情况，保留给未来扩展需要。
}
TableKey tkey = log.Bean.TableKey;
if (accessedRecords.TryGetValue(tkey, out var record))
{
record.Dirty = true;
}
else
{
logger.Fatal("impossible! record not found."); // 只有测试代码会把非 Managed 的 Bean 的日志加进来。
}
}
}
bool conflict = false; // 冲突了，也继续加锁，为重做做准备！！！
if (holdLocks.Count == 0)
{
foreach (var e in accessedRecords)
{
switch (_lock_and_check_(e))
{
case CheckResult.Success: break;
case CheckResult.Redo: conflict = true; break; // continue lock
case CheckResult.RedoAndReleaseLock: return(CheckResult.RedoAndReleaseLock);
}
}
return(conflict ? CheckResult.Redo : CheckResult.Success);
}
int index = 0;
int n = holdLocks.Count;
foreach (var e in accessedRecords)
{
// 如果 holdLocks 全部被对比完毕，直接锁定它
if (index >= n)
{
switch (_lock_and_check_(e))
{
case CheckResult.Success: break;
case CheckResult.Redo: conflict = true; break; // continue lock
case CheckResult.RedoAndReleaseLock: return(CheckResult.RedoAndReleaseLock);
}
continue;
}
Lockey curLock = holdLocks[index];
int c = curLock.TableKey.CompareTo(e.Key);
// holdlocks a b ...
// needlocks a b ...
if (c == 0)
{
// 这里可能发生读写锁提升
if (e.Value.Dirty && false == curLock.isWriteLockHeld())
{
curLock.EnterLock(true);
switch (_check_(true, e.Value))
{
case CheckResult.Success: break;
case CheckResult.Redo: conflict = true; break; // continue lock
case CheckResult.RedoAndReleaseLock: return(CheckResult.RedoAndReleaseLock);
}
}
// else 已经持有读锁，不可能被修改也不可能降级(reduce)，所以不做检测了。
// 已经锁定了，跳过
++index;
continue;
}
// holdlocks a b ...
// needlocks a c ...
if (c < 0)
{
// 释放掉 比当前锁序小的锁，因为当前事务中不再需要这些锁
int unlockEndIndex = index;
for (; unlockEndIndex < n && holdLocks[unlockEndIndex].TableKey.CompareTo(e.Key) < 0; ++unlockEndIndex)
{
var toUnlockLocker = holdLocks[unlockEndIndex];
toUnlockLocker.ExitLock();
}
holdLocks.RemoveRange(index, unlockEndIndex - index);
n = holdLocks.Count;
continue;
}
// holdlocks a c ...
// needlocks a b ...
// 为了不违背锁序，释放从当前锁开始的所有锁
for (int i = index; i < n; ++i)
{
var toUnlockLocker = holdLocks[i];
toUnlockLocker.ExitLock();
}
holdLocks.RemoveRange(index, n - index);
n = holdLocks.Count;
}
return(conflict ? CheckResult.Redo : CheckResult.Success);
}
