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Merge pull request #2504 from oleksii-datsiuk/fix-empty-page-must-be-…
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…defined-as-empty-type

Fix "ENSURE: empty page must be defined as empty type"
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@mbdavid
mbdavid authored Jul 3, 2024
2 parents b82f30e + 73f586e commit ca3f905
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Showing 3 changed files with 62 additions and 38 deletions.
38 changes: 24 additions & 14 deletions LiteDB/Engine/Services/SnapShot.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -159,18 +159,18 @@ public void Dispose()
#region Page Version functions

/// <summary>
/// Get a a valid page for this snapshot (must consider local-index and wal-index)
/// Get a valid page for this snapshot (must consider local-index and wal-index)
/// </summary>
public T GetPage<T>(uint pageID)
public T GetPage<T>(uint pageID, bool useLatestVersion = false)
where T : BasePage
{
return this.GetPage<T>(pageID, out var origin, out var position, out var walVersion);
return this.GetPage<T>(pageID, out var origin, out var position, out var walVersion, useLatestVersion);
}

/// <summary>
/// Get a a valid page for this snapshot (must consider local-index and wal-index)
/// Get a valid page for this snapshot (must consider local-index and wal-index)
/// </summary>
public T GetPage<T>(uint pageID, out FileOrigin origin, out long position, out int walVersion)
public T GetPage<T>(uint pageID, out FileOrigin origin, out long position, out int walVersion, bool useLatestVersion = false)
where T : BasePage
{
ENSURE(!_disposed, "the snapshot is disposed");
Expand Down Expand Up @@ -198,7 +198,7 @@ public T GetPage<T>(uint pageID, out FileOrigin origin, out long position, out i
}

// if page is not in local cache, get from disk (log/wal/data)
page = this.ReadPage<T>(pageID, out origin, out position, out walVersion);
page = this.ReadPage<T>(pageID, out origin, out position, out walVersion, useLatestVersion);

// add into local pages
_localPages[pageID] = page;
Expand All @@ -212,7 +212,7 @@ public T GetPage<T>(uint pageID, out FileOrigin origin, out long position, out i
/// <summary>
/// Read page from disk (dirty, wal or data)
/// </summary>
private T ReadPage<T>(uint pageID, out FileOrigin origin, out long position, out int walVersion)
private T ReadPage<T>(uint pageID, out FileOrigin origin, out long position, out int walVersion, bool useLatestVersion = false)
where T : BasePage
{
// if not inside local pages can be a dirty page saved in log file
Expand All @@ -232,7 +232,7 @@ private T ReadPage<T>(uint pageID, out FileOrigin origin, out long position, out
}

// now, look inside wal-index
var pos = _walIndex.GetPageIndex(pageID, _readVersion, out walVersion);
var pos = _walIndex.GetPageIndex(pageID, useLatestVersion ? int.MaxValue : _readVersion, out walVersion);

if (pos != long.MaxValue)
{
Expand Down Expand Up @@ -352,7 +352,7 @@ public T NewPage<T>()
// try get page from Empty free list
if (_header.FreeEmptyPageList != uint.MaxValue)
{
var free = this.GetPage<BasePage>(_header.FreeEmptyPageList);
var free = this.GetPage<BasePage>(_header.FreeEmptyPageList, useLatestVersion: true);

ENSURE(free.PageType == PageType.Empty, "empty page must be defined as empty type");

Expand All @@ -375,11 +375,21 @@ public T NewPage<T>()

if (newLength > _header.Pragmas.LimitSize) throw new LiteException(0, $"Maximum data file size has been reached: {FileHelper.FormatFileSize(_header.Pragmas.LimitSize)}");

// increase LastPageID from shared page
pageID = ++_header.LastPageID;

// request for a new buffer
buffer = _reader.NewPage();
var savepoint = _header.Savepoint();
try
{
// increase LastPageID from shared page
pageID = ++_header.LastPageID;

// request for a new buffer
buffer = _reader.NewPage();
}
catch
{
// must revert all header content if any error occurs during header change
_header.Restore(savepoint);
throw;
}
}

// retain a list of created pages to, in a rollback situation, back pages to empty list
Expand Down
45 changes: 22 additions & 23 deletions LiteDB/Engine/Services/TransactionService.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -205,29 +205,25 @@ IEnumerable<PageBuffer> source()
// in commit with header page change, last page will be header
if (commit && _transPages.HeaderChanged)
{
lock(_header)
{
// update this confirm page with current transactionID
_header.TransactionID = _transactionID;
// update this confirm page with current transactionID
_header.TransactionID = _transactionID;

// this header page will be marked as confirmed page in log file
_header.IsConfirmed = true;
// this header page will be marked as confirmed page in log file
_header.IsConfirmed = true;

// invoke all header callbacks (new/drop collections)
_transPages.OnCommit(_header);
// invoke all header callbacks (new/drop collections)
_transPages.OnCommit(_header);

// clone header page
var buffer = _header.UpdateBuffer();
var clone = _disk.NewPage();
// clone header page
var buffer = _header.UpdateBuffer();
var clone = _disk.NewPage();

// mem copy from current header to new header clone
Buffer.BlockCopy(buffer.Array, buffer.Offset, clone.Array, clone.Offset, clone.Count);
// mem copy from current header to new header clone
Buffer.BlockCopy(buffer.Array, buffer.Offset, clone.Array, clone.Offset, clone.Count);

// persist header in log file
yield return clone;
}
// persist header in log file
yield return clone;
}

};

// write all dirty pages, in sequence on log-file and store references into log pages on transPages
Expand Down Expand Up @@ -256,13 +252,16 @@ public void Commit()

if (_mode == LockMode.Write || _transPages.HeaderChanged)
{
// persist all dirty page as commit mode (mark last page as IsConfirm)
var count = this.PersistDirtyPages(true);

// update wal-index (if any page was added into log disk)
if(count > 0)
lock (_header)
{
_walIndex.ConfirmTransaction(_transactionID, _transPages.DirtyPages.Values);
// persist all dirty page as commit mode (mark last page as IsConfirm)
var count = this.PersistDirtyPages(true);

// update wal-index (if any page was added into log disk)
if (count > 0)
{
_walIndex.ConfirmTransaction(_transactionID, _transPages.DirtyPages.Values);
}
}
}

Expand Down
17 changes: 16 additions & 1 deletion LiteDB/Engine/Services/WalIndexService.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -38,7 +38,22 @@ public WalIndexService(DiskService disk, LockService locker)
/// <summary>
/// Get current read version for all new transactions
/// </summary>
public int CurrentReadVersion => _currentReadVersion;
public int CurrentReadVersion
{
get
{
_indexLock.TryEnterReadLock(-1);

try
{
return _currentReadVersion;
}
finally
{
_indexLock.ExitReadLock();
}
}
}

/// <summary>
/// Get current counter for transaction ID
Expand Down

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