From 69ae228549978f0008ae604963122e2b8f33f8ed Mon Sep 17 00:00:00 2001
From: mbdavid <mauricio.david@gmail.com>
Date: Wed, 15 Feb 2017 07:57:37 -0200
Subject: [PATCH] Avoid Storage use Transaction and OpenWrite delete in chunks
 #484

---
 LiteDB/Engine/Engine/Transaction.cs |  5 +++++
 LiteDB/Storage/LiteFileStream.cs    | 13 +++++++++++--
 LiteDB/Storage/LiteStorage.cs       |  3 ++-
 LiteDB/Utils/LiteException.cs       |  6 ++++++
 4 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/LiteDB/Engine/Engine/Transaction.cs b/LiteDB/Engine/Engine/Transaction.cs
index 51e9abc6f..a15361d4c 100644
--- a/LiteDB/Engine/Engine/Transaction.cs
+++ b/LiteDB/Engine/Engine/Transaction.cs
@@ -9,6 +9,11 @@ public partial class LiteEngine : IDisposable
     {
         private Stack<LockControl> _transactions = new Stack<LockControl>();
 
+        /// <summary>
+        /// Get transaction stack count. If returns 0, there is no transaction.
+        /// </summary>
+        internal int TransactionCount { get { return _transactions.Count; } }
+
         /// <summary>
         /// Starts a new transaction keeping all changed from now in memory only until Commit() be executed.
         /// Lock thread in write mode to not accept other transaction
diff --git a/LiteDB/Storage/LiteFileStream.cs b/LiteDB/Storage/LiteFileStream.cs
index c54154f03..b3a130651 100644
--- a/LiteDB/Storage/LiteFileStream.cs
+++ b/LiteDB/Storage/LiteFileStream.cs
@@ -27,7 +27,9 @@ internal LiteFileStream(LiteEngine engine, LiteFileInfo file, FileAccess mode)
             _file = file;
             _mode = mode;
 
-            if(mode == FileAccess.Read)
+            if (_engine.TransactionCount > 0) throw LiteException.TransactionNotSupported("LiteFileStream");
+
+            if (mode == FileAccess.Read)
             {
                 // initialize first data block
                 _currentChunkData = this.GetChunkData(_currentChunkIndex);
@@ -39,7 +41,14 @@ internal LiteFileStream(LiteEngine engine, LiteFileInfo file, FileAccess mode)
                 // delete chunks content if needed
                 if (file.Length > 0)
                 {
-                    _engine.Delete(LiteStorage.CHUNKS, Query.StartsWith("_id", _file.Id + "\\"));
+                    var index = 0;
+                    var deleted = true;
+
+                    // delete one-by-one to avoid all pages files dirty in memory
+                    while (deleted)
+                    {
+                        deleted = _engine.Delete(LiteStorage.CHUNKS, LiteFileStream.GetChunckId(_file.Id, index++)); // index zero based
+                    }
                 }
 
                 // clear size counters
diff --git a/LiteDB/Storage/LiteStorage.cs b/LiteDB/Storage/LiteStorage.cs
index 51fd3cbc2..a6a576685 100644
--- a/LiteDB/Storage/LiteStorage.cs
+++ b/LiteDB/Storage/LiteStorage.cs
@@ -6,7 +6,7 @@
 namespace LiteDB
 {
     /// <summary>
-    /// Storage is a special collection to store files/streams.
+    /// Storage is a special collection to store files/streams. Transactions are not supported in Upload/Download operations.
     /// </summary>
     public class LiteStorage
     {
@@ -194,6 +194,7 @@ public IEnumerable<LiteFileInfo> FindAll()
         /// </summary>
         public bool Delete(string id)
         {
+            if (_engine.TransactionCount > 0) throw LiteException.TransactionNotSupported("LiteStorage.Delete");
             if (id.IsNullOrWhiteSpace()) throw new ArgumentNullException("id");
 
             // remove file reference in _files
diff --git a/LiteDB/Utils/LiteException.cs b/LiteDB/Utils/LiteException.cs
index 054c657e3..30baea819 100644
--- a/LiteDB/Utils/LiteException.cs
+++ b/LiteDB/Utils/LiteException.cs
@@ -29,6 +29,7 @@ public class LiteException : Exception
         public const int ALREADY_EXISTS_COLLECTION_NAME = 122;
         public const int DATABASE_WRONG_PASSWORD = 123;
         public const int READ_ONLY_DATABASE = 125;
+        public const int TRANSACTION_NOT_SUPPORTED = 126;
 
         public const int INVALID_FORMAT = 200;
         public const int DOCUMENT_MAX_DEPTH = 201;
@@ -156,6 +157,11 @@ internal static LiteException InvalidDbRef(string path)
             return new LiteException(INVALID_DBREF, "Invalid value for DbRef in path \"{0}\". Value must be document like {{ $ref: \"?\", $id: ? }}", path);
         }
 
+        internal static LiteException TransactionNotSupported(string method)
+        {
+            return new LiteException(TRANSACTION_NOT_SUPPORTED, "Transactions are not supported here: " + method);
+        }
+
         #endregion
 
         #region Document/Mapper Errors