diff --git a/index.bat b/index.bat
index 54c22724..5712b5a3 100644
--- a/index.bat
+++ b/index.bat
@@ -1 +1 @@
-sir.bat indexwikipedia --directory C:\projects\resin\src\Sir.HttpServer\AppData\database --collection wikipedia --skip 0 --take 200000 --pageSize 100000 --sampleSize 1000 %*
\ No newline at end of file
+sir.bat indexwikipedia --directory C:\projects\resin\src\Sir.HttpServer\AppData\database --collection wikipedia --skip 0 --take 100000 --pageSize 10000 --sampleSize 1000 %*
\ No newline at end of file
diff --git a/src/Sir.Document/DocmentMapReader.cs b/src/Sir.Document/DocmentMapReader.cs
index df3c7b79..cc912716 100644
--- a/src/Sir.Document/DocmentMapReader.cs
+++ b/src/Sir.Document/DocmentMapReader.cs
@@ -4,7 +4,7 @@
 namespace Sir.Documents
 {
     /// <summary>
-    /// Read document maps (key_id/val_id) from the document map stream.
+    /// Read document maps (key_id/val_id, each pair 2*sizeof(long)) from the document map stream.
     /// A document map is needed to re-contruct a complete document.
     /// </summary>
     public class DocmentMapReader : IDisposable
diff --git a/src/Sir.Document/DocumentIndexWriter.cs b/src/Sir.Document/DocumentIndexWriter.cs
index 4d924760..66307392 100644
--- a/src/Sir.Document/DocumentIndexWriter.cs
+++ b/src/Sir.Document/DocumentIndexWriter.cs
@@ -16,11 +16,6 @@ public DocumentIndexWriter(Stream stream)
             _stream = stream;
         }
 
-        public void Flush()
-        {
-            _stream.Flush();
-        }
-
         /// <summary>
         /// Get the next auto-incrementing doc id
         /// </summary>
diff --git a/src/Sir.Document/DocumentMapWriter.cs b/src/Sir.Document/DocumentMapWriter.cs
index d0a6895b..4ab9a5ec 100644
--- a/src/Sir.Document/DocumentMapWriter.cs
+++ b/src/Sir.Document/DocumentMapWriter.cs
@@ -5,7 +5,7 @@
 namespace Sir.Documents
 {
     /// <summary>
-    /// Writes document maps (key_id/val_id) to a bitmap.
+    /// Writes document maps (key_id/val_id, each pair 2*sizeof(long)) to a bitmap.
     /// </summary>
     public class DocumentMapWriter : IDisposable
     {
diff --git a/src/Sir.Document/DocumentReader.cs b/src/Sir.Document/DocumentReader.cs
index 0a3805d5..fec5ecee 100644
--- a/src/Sir.Document/DocumentReader.cs
+++ b/src/Sir.Document/DocumentReader.cs
@@ -21,7 +21,7 @@ public static Document Read(long documentId, DocumentRegistryReader documentRead
                     var vInfo = documentReader.GetAddressOfValue(kvp.valId);
                     var val = documentReader.GetValue(vInfo.offset, vInfo.len, vInfo.dataType);
 
-                    fields.Add(new Field(key, val, kvp.keyId));
+                    fields.Add(new Field(key, val, kvp.keyId, documentId));
                 }
             }
 
diff --git a/src/Sir.Document/DocumentRegistryWriter.cs b/src/Sir.Document/DocumentRegistryWriter.cs
index 1e3479d7..71ae042f 100644
--- a/src/Sir.Document/DocumentRegistryWriter.cs
+++ b/src/Sir.Document/DocumentRegistryWriter.cs
@@ -9,8 +9,8 @@ namespace Sir.Documents
     /// </summary>
     public class DocumentRegistryWriter : IDisposable
     {
-        private DocumentMapWriter _docs;
-        private DocumentIndexWriter _docIx;
+        private DocumentMapWriter _documentMapWriter;
+        private DocumentIndexWriter _documentIndexWriter;
         private KeyValueWriter _kvWriter;
         private readonly string _directory;
         private readonly ulong _collectionId;
@@ -19,8 +19,8 @@ public class DocumentRegistryWriter : IDisposable
 
         public DocumentRegistryWriter(string directory, ulong collectionId)
         {
-            _docs = new DocumentMapWriter(KeyValueWriter.CreateAppendStream(directory, collectionId, "docs"));
-            _docIx = new DocumentIndexWriter(KeyValueWriter.CreateAppendStream(directory, collectionId, "dix"));
+            _documentMapWriter = new DocumentMapWriter(KeyValueWriter.CreateAppendStream(directory, collectionId, "docs"));
+            _documentIndexWriter = new DocumentIndexWriter(KeyValueWriter.CreateAppendStream(directory, collectionId, "dix"));
             _kvWriter = new KeyValueWriter(directory, collectionId);
             _directory = directory;
             _collectionId = collectionId;
@@ -28,39 +28,39 @@ public DocumentRegistryWriter(string directory, ulong collectionId)
 
         public long IncrementDocId()
         {
-            return _docIx.IncrementDocId();
+            return _documentIndexWriter.IncrementDocId();
         }
 
         public (long offset, int length) PutDocumentMap(IList<(long keyId, long valId)> doc)
         {
-            return _docs.Put(doc);
+            return _documentMapWriter.Put(doc);
         }
 
         public void UpdateDocumentMap(long offsetOfMap, int indexInMap, long keyId, long valId)
         {
-            _docs.Overwrite(offsetOfMap, indexInMap, keyId, valId);
+            _documentMapWriter.Overwrite(offsetOfMap, indexInMap, keyId, valId);
         }
 
         public void PutDocumentAddress(long docId, long offset, int len)
         {
-            _docIx.Put(docId, offset, len);
+            _documentIndexWriter.Put(docId, offset, len);
         }
 
         public void Commit()
         {
-            _docs.Dispose();
-            _docIx.Dispose();
+            _documentMapWriter.Dispose();
+            _documentIndexWriter.Dispose();
             _kvWriter.Dispose();
 
-            _docs = new DocumentMapWriter(KeyValueWriter.CreateAppendStream(_directory, _collectionId, "docs"));
-            _docIx = new DocumentIndexWriter(KeyValueWriter.CreateAppendStream(_directory, _collectionId, "dix"));
+            _documentMapWriter = new DocumentMapWriter(KeyValueWriter.CreateAppendStream(_directory, _collectionId, "docs"));
+            _documentIndexWriter = new DocumentIndexWriter(KeyValueWriter.CreateAppendStream(_directory, _collectionId, "dix"));
             _kvWriter = new KeyValueWriter(_directory, _collectionId);
         }
 
         public void Dispose()
         {
-            _docs.Dispose();
-            _docIx.Dispose();
+            _documentMapWriter.Dispose();
+            _documentIndexWriter.Dispose();
             _kvWriter.Dispose();
         }
     }
diff --git a/src/Sir.InformationRetreival/Session/DocumentDatabase.cs b/src/Sir.InformationRetreival/Session/DocumentDatabase.cs
index c06dd91a..b2d41d38 100644
--- a/src/Sir.InformationRetreival/Session/DocumentDatabase.cs
+++ b/src/Sir.InformationRetreival/Session/DocumentDatabase.cs
@@ -28,8 +28,8 @@ public DocumentDatabase(string directory, ulong collectionId, IModel<T> model =
         {
             _directory = directory ?? throw new ArgumentNullException(nameof(directory));
             _collectionId = collectionId;
-            _model = model ?? throw new ArgumentNullException(nameof(model));
-            _indexStrategy = indexStrategy ?? throw new ArgumentNullException(nameof(indexStrategy));
+            _model = model;
+            _indexStrategy = indexStrategy;
             _writeSession = new WriteSession(new DocumentRegistryWriter(directory, collectionId));
             _indexSession = new IndexSession<T>(directory, collectionId, model, indexStrategy, logger);
             _searchSession = new SearchSession<T>(directory, _model, _indexStrategy, logger);
@@ -89,9 +89,6 @@ public void OptimizeAllIndices(int skipDocuments = 0, int takeDocuments = int.Ma
         public void Truncate()
         {
             DisposeInternal();
-            _writeSession = null;
-            _indexSession = null;
-            _searchSession = null;
 
             var count = 0;
 
@@ -153,9 +150,6 @@ public void TruncateIndexOnly()
         public void Rename(ulong newCollectionId)
         {
             DisposeInternal();
-            _writeSession = null;
-            _indexSession = null;
-            _searchSession = null;
 
             var count = 0;
             var from = _collectionId.ToString();
@@ -186,7 +180,7 @@ private void LogInformation(string message)
                 _logger.LogInformation(message);
         }
 
-        public void Commit()
+        public void CommitIndexAndClearSearchCache()
         {
             _writeSession.Commit();
             _indexSession.Commit();
@@ -195,7 +189,7 @@ public void Commit()
 
         public void Dispose()
         {
-            Commit();
+            CommitIndexAndClearSearchCache();
             DisposeInternal();
         }
 
diff --git a/src/Sir.InformationRetreival/Session/WriteSession.cs b/src/Sir.InformationRetreival/Session/WriteSession.cs
index 98724f25..38ef68ff 100644
--- a/src/Sir.InformationRetreival/Session/WriteSession.cs
+++ b/src/Sir.InformationRetreival/Session/WriteSession.cs
@@ -29,7 +29,7 @@ public void Put(Document document)
 
                 if (field.Value != null)
                 {
-                    Write(field, docMap);
+                    WriteField(field, docMap);
                 }
             }
 
@@ -38,7 +38,7 @@ public void Put(Document document)
             _documentWriter.PutDocumentAddress(document.Id, docMeta.offset, docMeta.length);
         }
 
-        private void Write(Field field, IList<(long, long)> docMap)
+        private void WriteField(Field field, IList<(long, long)> docMap)
         {
             field.KeyId = EnsureKeyExists(field.Name);
 
@@ -59,11 +59,6 @@ public long EnsureKeyExists(string key)
             return _documentWriter.KeyValueWriter.EnsureKeyExists(key);
         }
 
-        public long EnsureKeyExistsSafely(string key)
-        {
-            return _documentWriter.KeyValueWriter.EnsureKeyExistsSafely(key);
-        }
-
         public void Commit()
         {
             _documentWriter.Commit();
diff --git a/src/Sir.KeyValue/KeyValueReader.cs b/src/Sir.KeyValue/KeyValueReader.cs
index ddb392c7..d525f521 100644
--- a/src/Sir.KeyValue/KeyValueReader.cs
+++ b/src/Sir.KeyValue/KeyValueReader.cs
@@ -48,10 +48,24 @@ public bool TryGetKeyId(ulong keyHash, out long keyId)
             if (!_keyCache.TryGetValue(key, out keys))
             {
                 ReadKeysIntoCache();
+
+                if (!_keyCache.TryGetValue(key, out keys))
+                {
+                    // there are no keys registered for this collection, even on disk.
+
+                    keyId = -1;
+                    return false;
+                }
             }
 
-            if (keys != null || _keyCache.TryGetValue(key, out keys))
+            if (keys.TryGetValue(keyHash, out keyId))
+            {
+                return true;
+            }
+            else
             {
+                ReadKeysIntoCache();
+
                 if (keys.TryGetValue(keyHash, out keyId))
                 {
                     return true;
@@ -64,31 +78,29 @@ public bool TryGetKeyId(ulong keyHash, out long keyId)
 
         private void ReadKeysIntoCache()
         {
+            _keyCache.Clear();
+
             foreach (var keyFile in System.IO.Directory.GetFiles(_directory, "*.kmap"))
             {
                 var collectionId = ulong.Parse(Path.GetFileNameWithoutExtension(keyFile));
                 var key = Path.Combine(_directory, collectionId.ToString()).ToHash();
+                var keys = new ConcurrentDictionary<ulong, long>();
 
-                var keys = _keyCache.GetOrAdd(key, (k) =>
+                using (var stream = new FileStream(keyFile, FileMode.OpenOrCreate, FileAccess.Read, FileShare.ReadWrite))
                 {
-                    var ks = new ConcurrentDictionary<ulong, long>();
+                    long i = 0;
+                    var buf = new byte[sizeof(ulong)];
+                    var read = stream.Read(buf, 0, buf.Length);
 
-                    using (var stream = new FileStream(keyFile, FileMode.OpenOrCreate, FileAccess.Read, FileShare.ReadWrite))
+                    while (read > 0)
                     {
-                        long i = 0;
-                        var buf = new byte[sizeof(ulong)];
-                        var read = stream.Read(buf, 0, buf.Length);
-
-                        while (read > 0)
-                        {
-                            ks.TryAdd(BitConverter.ToUInt64(buf, 0), i++);
+                        keys.TryAdd(BitConverter.ToUInt64(buf, 0), i++);
 
-                            read = stream.Read(buf, 0, buf.Length);
-                        }
+                        read = stream.Read(buf, 0, buf.Length);
                     }
+                }
 
-                    return ks;
-                });
+                _keyCache.GetOrAdd(key, keys);
             }
         }
 
diff --git a/src/Sir.KeyValue/KeyValueWriter.cs b/src/Sir.KeyValue/KeyValueWriter.cs
index 5350a886..07b983f9 100644
--- a/src/Sir.KeyValue/KeyValueWriter.cs
+++ b/src/Sir.KeyValue/KeyValueWriter.cs
@@ -15,9 +15,8 @@ public class KeyValueWriter : IDisposable
         private readonly ValueIndexWriter _keyIx;
         private readonly ulong _collectionId;
         private readonly string _directory;
-        private readonly object _keyLock = new object();
-        private ConcurrentDictionary<ulong, ConcurrentDictionary<ulong, long>> _keyCache;
         private readonly KeyValueReader _kvReader;
+        private static object _keyLock = new object();
 
         public KeyValueWriter(string directory, ulong collectionId)
             : this(
@@ -29,7 +28,6 @@ public KeyValueWriter(string directory, ulong collectionId)
         {
             _collectionId = collectionId;
             _directory = directory;
-            _keyCache = new ConcurrentDictionary<ulong, ConcurrentDictionary<ulong, long>>();
             _kvReader = new KeyValueReader(directory, collectionId);
         }
 
@@ -75,7 +73,7 @@ public static Stream CreateAppendStream(string directory, ulong collectionId, lo
             return new FileStream(fileName, FileMode.Append, FileAccess.Write, FileShare.ReadWrite);
         }
 
-        public long EnsureKeyExistsSafely(string keyStr)
+        public long EnsureKeyExists(string keyStr)
         {
             var keyHash = keyStr.ToHash();
             long keyId;
@@ -94,7 +92,10 @@ public long EnsureKeyExistsSafely(string keyStr)
                         keyId = PutKeyInfo(keyInfo.offset, keyInfo.len, keyInfo.dataType);
 
                         // store key mapping
-                        RegisterKeyMapping(_directory, _collectionId, keyHash, keyId);
+                        using (var stream = CreateAppendStream(_directory, _collectionId, "kmap"))
+                        {
+                            stream.Write(BitConverter.GetBytes(keyHash), 0, sizeof(ulong));
+                        }
                     }
                 }
             }
@@ -102,27 +103,6 @@ public long EnsureKeyExistsSafely(string keyStr)
             return keyId;
         }
 
-        public long EnsureKeyExists(string keyStr)
-        {
-            var keyHash = keyStr.ToHash();
-            long keyId;
-
-            if (!_kvReader.TryGetKeyId(keyHash, out keyId))
-            {
-                // We have a new key!
-
-                // store key
-                var keyInfo = PutKey(keyStr);
-
-                keyId = PutKeyInfo(keyInfo.offset, keyInfo.len, keyInfo.dataType);
-
-                // store key mapping
-                RegisterKeyMapping(_directory, _collectionId, keyHash, keyId);
-            }
-
-            return keyId;
-        }
-
         public (long keyId, long valueId) PutValue(long keyId, object val, out byte dataType)
         {
             // store value
@@ -164,20 +144,6 @@ public void OverwriteFixedLengthValue(long offset, object value, Type type)
             _vals.Put(value);
         }
 
-        public void RegisterKeyMapping(string directory, ulong collectionId, ulong keyHash, long keyId)
-        {
-            var key = Path.Combine(directory, collectionId.ToString()).ToHash();
-            var keys = _keyCache.GetOrAdd(key, (key) => { return new ConcurrentDictionary<ulong, long>(); });
-            var keyMapping = keys.GetOrAdd(keyHash, (key) =>
-            {
-                using (var stream = CreateAppendStream(directory, collectionId, "kmap"))
-                {
-                    stream.Write(BitConverter.GetBytes(keyHash), 0, sizeof(ulong));
-                }
-                return keyId;
-            });
-        }
-
         public void Dispose()
         {
             _vals.Dispose();
diff --git a/src/Sir.StringTests/BagOfCharsDatabaseTests.cs b/src/Sir.StringTests/BagOfCharsDatabaseTests.cs
index b63991b8..9ae53786 100644
--- a/src/Sir.StringTests/BagOfCharsDatabaseTests.cs
+++ b/src/Sir.StringTests/BagOfCharsDatabaseTests.cs
@@ -32,7 +32,7 @@ public void Can_stream()
                     database.Write(document, index: false);
                 }
 
-                database.Commit();
+                database.CommitIndexAndClearSearchCache();
 
                 var i = 0;
 
@@ -69,7 +69,7 @@ public void Can_read_and_write()
                     database.Write(document);
                 }
 
-                database.Commit();
+                database.CommitIndexAndClearSearchCache();
 
                 var queryParser = database.CreateQueryParser();
 
@@ -109,7 +109,7 @@ public void Can_optimize_index()
                     database.Write(document, store:true, index:false); // note: no indexing going on here
                 }
 
-                database.Commit();
+                database.CommitIndexAndClearSearchCache();
 
                 var queryParser = database.CreateQueryParser();
 
diff --git a/write.bat b/write.bat
index 2e937d90..5db8472a 100644
--- a/write.bat
+++ b/write.bat
@@ -1 +1 @@
-sir.bat writewikipedia --directory C:\projects\resin\src\Sir.HttpServer\AppData\database --file d:\enwiki-20211122-cirrussearch-content.json.gz --collection wikipedia --skip 100000 --take 100000 --sampleSize 10000 %*
\ No newline at end of file
+sir.bat writewikipedia --directory C:\projects\resin\src\Sir.HttpServer\AppData\database --file d:\enwiki-20211122-cirrussearch-content.json.gz --collection wikipedia --skip 0 --take 10000 --sampleSize 1000 %*
\ No newline at end of file