private Page GetPageInternal(long pageNumber)
{
// Check if we can hit the lowest level locality cache.
Page p;
PageFromScratchBuffer value;
if (_scratchPagesTable != null && _scratchPagesTable.TryGetValue(pageNumber, out value)) // Scratch Pages Table will be null in read transactions
{
Debug.Assert(value != null);
PagerState state = null;
if (_scratchPagerStates != null)
{
var lastUsed = _lastScratchFileUsed;
if (lastUsed.FileNumber == value.ScratchFileNumber)
{
state = lastUsed.State;
}
else
{
state = _scratchPagerStates[value.ScratchFileNumber];
_lastScratchFileUsed = new PagerStateCacheItem(value.ScratchFileNumber, state);
}
}
p = _env.ScratchBufferPool.ReadPage(this, value.ScratchFileNumber, value.PositionInScratchBuffer, state);
Debug.Assert(p.PageNumber == pageNumber, string.Format("Requested ReadOnly page #{0}. Got #{1} from scratch", pageNumber, p.PageNumber));
}
else
{
var pageFromJournal = _journal.ReadPage(this, pageNumber, _scratchPagerStates);
if (pageFromJournal != null)
{
p = pageFromJournal.Value;
Debug.Assert(p.PageNumber == pageNumber, string.Format("Requested ReadOnly page #{0}. Got #{1} from journal", pageNumber, p.PageNumber));
}
else
{
p = new Page(DataPager.AcquirePagePointerWithOverflowHandling(this, pageNumber));
Debug.Assert(p.PageNumber == pageNumber, string.Format("Requested ReadOnly page #{0}. Got #{1} from data file", pageNumber, p.PageNumber));
// When encryption is off, we do validation by checksum
if (_env.Options.EncryptionEnabled == false)
{
_env.ValidatePageChecksum(pageNumber, (PageHeader *)p.Pointer);
}
}
}
TrackReadOnlyPage(p);
_pageLocator.SetReadable(p.PageNumber, p);
return(p);
}