Add control of cache update policy when an item changes value.

7 files changed, 115 insertions, 109 deletions

diff --git a/searchlib/src/tests/docstore/logdatastore/logdatastore_test.cpp b/searchlib/src/tests/docstore/logdatastore/logdatastore_test.cpp
index a22c44e843c..80471235d1b 100644
--- a/searchlib/src/tests/docstore/logdatastore/logdatastore_test.cpp
+++ b/searchlib/src/tests/docstore/logdatastore/logdatastore_test.cpp
@@ -282,13 +282,13 @@ TEST("testTruncatedIdxFile"){
     {
         // Files comes from the 'growing test'.
         LogDataStore datastore(executor, TEST_PATH("bug-7257706"), config, GrowStrategy(),
-                               TuneFileSummary(), fileHeaderContext, tlSyncer, NULL);
+                               TuneFileSummary(), fileHeaderContext, tlSyncer, nullptr);
         EXPECT_EQUAL(354ul, datastore.lastSyncToken());
     }
     const char * magic = "mumbo jumbo";
     {
         LogDataStore datastore(executor, "bug-7257706-truncated", config, GrowStrategy(),
-                               TuneFileSummary(), fileHeaderContext, tlSyncer, NULL);
+                               TuneFileSummary(), fileHeaderContext, tlSyncer, nullptr);
         EXPECT_EQUAL(331ul, datastore.lastSyncToken());
         datastore.write(332, 7, magic, strlen(magic));
         datastore.write(333, 8, magic, strlen(magic));
@@ -296,7 +296,7 @@ TEST("testTruncatedIdxFile"){
     }
     {
         LogDataStore datastore(executor, "bug-7257706-truncated", config, GrowStrategy(),
-                               TuneFileSummary(), fileHeaderContext, tlSyncer, NULL);
+                               TuneFileSummary(), fileHeaderContext, tlSyncer, nullptr);
         EXPECT_EQUAL(334ul, datastore.lastSyncToken());
     }
 }
@@ -308,7 +308,7 @@ TEST("testThatEmptyIdxFilesAndDanglingDatFilesAreRemoved") {
     MyTlSyncer tlSyncer;
     LogDataStore datastore(executor, "dangling-test", config,
                            GrowStrategy(), TuneFileSummary(),
-                           fileHeaderContext, tlSyncer, NULL);
+                           fileHeaderContext, tlSyncer, nullptr);
     EXPECT_EQUAL(354ul, datastore.lastSyncToken());
     EXPECT_EQUAL(4096u + 480u, datastore.getDiskHeaderFootprint());
     EXPECT_EQUAL(datastore.getDiskHeaderFootprint() + 94016u, datastore.getDiskFootprint());
@@ -321,7 +321,7 @@ TEST("testThatIncompleteCompactedFilesAreRemoved") {
     MyTlSyncer tlSyncer;
     LogDataStore datastore(executor, "incompletecompact-test", config,
                            GrowStrategy(), TuneFileSummary(),
-                           fileHeaderContext, tlSyncer, NULL);
+                           fileHeaderContext, tlSyncer, nullptr);
     EXPECT_EQUAL(354ul, datastore.lastSyncToken());
     EXPECT_EQUAL(3*(4096u + 480u), datastore.getDiskHeaderFootprint());
     LogDataStore::NameIdSet files = datastore.getAllActiveFiles();
@@ -340,7 +340,7 @@ public:
         _executor(1, 128*1024),
         _tlSyncer(),
         _datastore(_executor, _myDir.getDir(), _config, GrowStrategy(),
-                   TuneFileSummary(), _fileHeaderContext, _tlSyncer, NULL)
+                   TuneFileSummary(), _fileHeaderContext, _tlSyncer, nullptr)
     { }
     ~VisitStore();
     IDataStore & getStore() { return _datastore; }
@@ -524,7 +524,7 @@ VisitCacheStore::VisitCacheStore() :
     _inserted(),
     _serial(1)
 { }
-VisitCacheStore::~VisitCacheStore() {}
+VisitCacheStore::~VisitCacheStore() = default;
 
 void
 verifyCacheStats(CacheStats cs, size_t hits, size_t misses, size_t elements, size_t memory_used) {
@@ -546,41 +546,42 @@ TEST("test that the integrated visit cache works.") {
     for (size_t i(1); i <= 100; i++) {
         vcs.verifyRead(i);
     }
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 0, 100, 100, 20574));
+    constexpr size_t BASE_SZ = 21374;
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 0, 100, 100, BASE_SZ));
     for (size_t i(1); i <= 100; i++) {
         vcs.verifyRead(i);
     }
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 100, 100, 100, 20574)); // From the individual cache.
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 100, 100, 100, BASE_SZ)); // From the individual cache.
 
     vcs.verifyVisit({7,9,17,19,67,88}, false);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 100, 100, 100, 20574));
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 100, 100, 100, BASE_SZ));
     vcs.verifyVisit({7,9,17,19,67,88}, true);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 100, 101, 101, 21135));
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 100, 101, 101, BASE_SZ+557));
     vcs.verifyVisit({7,9,17,19,67,88}, true);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 101, 101, 21135));
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 101, 101, BASE_SZ+557));
     vcs.rewrite(8);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 101, 100, 20922)); // From the individual cache.
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 101, 100, BASE_SZ+328)); // From the individual cache.
     vcs.rewrite(7);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 101, 98, 20148)); // From the both caches.
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 101, 98, BASE_SZ-442)); // From the both caches.
     vcs.verifyVisit({7,9,17,19,67,88}, true);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 102, 99, 20732));
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 102, 99, BASE_SZ+130));
     vcs.verifyVisit({7,9,17,19,67,88,89}, true);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 103, 99, 20783));
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 103, 99, BASE_SZ+201));
     vcs.rewrite(17);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 103, 97, 19943));
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 103, 97, BASE_SZ-657));
     vcs.verifyVisit({7,9,17,19,67,88,89}, true);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 104, 98, 20587));
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 104, 98, BASE_SZ-3));
     vcs.remove(17);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 104, 97, 19943));
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 104, 97, BASE_SZ-657));
     vcs.verifyVisit({7,9,17,19,67,88,89}, {7,9,19,67,88,89}, true);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 105, 98, 20526));
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 105, 98, BASE_SZ-64));
 
     vcs.verifyVisit({41, 42}, true);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 106, 99, 20820));
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 106, 99, BASE_SZ+238));
     vcs.verifyVisit({43, 44}, true);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 107, 100, 21124));
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 107, 100, BASE_SZ+540));
     vcs.verifyVisit({41, 42, 43, 44}, true);
-    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 108, 99, 20944));
+    TEST_DO(verifyCacheStats(ds.getCacheStats(), 101, 108, 99, BASE_SZ+362));
 }
 
 TEST("testWriteRead") {
@@ -595,7 +596,7 @@ TEST("testWriteRead") {
         vespalib::ThreadStackExecutor executor(1, 128*1024);
         MyTlSyncer tlSyncer;
         LogDataStore datastore(executor, "empty", config, GrowStrategy(),
-                               TuneFileSummary(), fileHeaderContext, tlSyncer, NULL);
+                               TuneFileSummary(), fileHeaderContext, tlSyncer, nullptr);
         ASSERT_TRUE(datastore.lastSyncToken() == 0);
         size_t headerFootprint = datastore.getDiskHeaderFootprint();
         EXPECT_LESS(0u, headerFootprint);
@@ -606,7 +607,7 @@ TEST("testWriteRead") {
         fetchAndTest(datastore, 0, a[0].c_str(), a[0].size());
         datastore.write(2, 0, a[1].c_str(), a[1].size());
         fetchAndTest(datastore, 0, a[1].c_str(), a[1].size());
-        fetchAndTest(datastore, 1, NULL, 0);
+        fetchAndTest(datastore, 1, nullptr, 0);
         datastore.remove(3, 0);
         fetchAndTest(datastore, 0, "", 0);
 
@@ -632,7 +633,7 @@ TEST("testWriteRead") {
         MyTlSyncer tlSyncer;
         LogDataStore datastore(executor, "empty", config,
                                GrowStrategy(), TuneFileSummary(),
-                               fileHeaderContext, tlSyncer, NULL);
+                               fileHeaderContext, tlSyncer, nullptr);
         size_t headerFootprint = datastore.getDiskHeaderFootprint();
         EXPECT_LESS(0u, headerFootprint);
         EXPECT_EQUAL(4944ul + headerFootprint, datastore.getDiskFootprint());
diff --git a/searchlib/src/vespa/searchlib/attribute/attribute_header.cpp b/searchlib/src/vespa/searchlib/attribute/attribute_header.cpp
index 4a69e0a827d..828c7c19962 100644
--- a/searchlib/src/vespa/searchlib/attribute/attribute_header.cpp
+++ b/searchlib/src/vespa/searchlib/attribute/attribute_header.cpp
@@ -68,9 +68,7 @@ AttributeHeader::AttributeHeader(const vespalib::string &fileName,
 {
 }
 
-AttributeHeader::~AttributeHeader()
-{
-}
+AttributeHeader::~AttributeHeader() = default;
 
 void
 AttributeHeader::internalExtractTags(const vespalib::GenericHeader &header)
diff --git a/searchlib/src/vespa/searchlib/attribute/attribute_header.h b/searchlib/src/vespa/searchlib/attribute/attribute_header.h
index 3d00396e171..4a0b1e0bee0 100644
--- a/searchlib/src/vespa/searchlib/attribute/attribute_header.h
+++ b/searchlib/src/vespa/searchlib/attribute/attribute_header.h
@@ -10,8 +10,7 @@
 
 namespace vespalib { class GenericHeader; }
 
-namespace search {
-namespace attribute {
+namespace search::attribute {
 
 /**
  * Attribute header class used by attribute savers and attribute initializer
@@ -71,5 +70,4 @@ public:
     void addTags(vespalib::GenericHeader &header) const;
 };
 
-} // namespace search::attribute
-} // namespace search
+}
diff --git a/searchlib/src/vespa/searchlib/attribute/attributefilewriter.cpp b/searchlib/src/vespa/searchlib/attribute/attributefilewriter.cpp
index b1268aacc4f..415c00cb8fd 100644
--- a/searchlib/src/vespa/searchlib/attribute/attributefilewriter.cpp
+++ b/searchlib/src/vespa/searchlib/attribute/attributefilewriter.cpp
@@ -2,10 +2,10 @@
 
 #include "attributefilewriter.h"
 #include "attributefilebufferwriter.h"
+#include "attribute_header.h"
 #include <vespa/vespalib/data/fileheader.h>
 #include <vespa/searchlib/common/fileheadercontext.h>
 #include <vespa/searchlib/common/tunefileinfo.h>
-#include "attribute_header.h"
 #include <vespa/fastos/file.h>
 
 #include <vespa/log/log.h>
@@ -14,7 +14,6 @@ LOG_SETUP(".searchlib.attribute.attributefilewriter");
 using search::common::FileHeaderContext;
 using vespalib::getLastErrorString;
 
-
 namespace search {
 
 namespace {
@@ -23,8 +22,7 @@ const uint32_t headerAlign = 4096;
 const uint32_t MIN_ALIGNMENT = 4096;
 
 void
-writeDirectIOAligned(FastOS_FileInterface &file, const void *buf,
-                     size_t length)
+writeDirectIOAligned(FastOS_FileInterface &file, const void *buf, size_t length)
 {
     const char * data(static_cast<const char *>(buf));
     size_t remaining(length);
@@ -38,7 +36,6 @@ writeDirectIOAligned(FastOS_FileInterface &file, const void *buf,
     }
 }
 
-
 void
 updateHeader(const vespalib::string &name, uint64_t fileBitSize)
 {
@@ -63,29 +60,22 @@ class FileBackedBufferWriter : public AttributeFileBufferWriter
 {
 public:
     FileBackedBufferWriter(AttributeFileWriter &fileWriter);
+    ~FileBackedBufferWriter() override;
 
-    virtual ~FileBackedBufferWriter();
-
-    virtual void onFlush(size_t nowLen) override;
+    void onFlush(size_t nowLen) override;
 };
 
 
 FileBackedBufferWriter::FileBackedBufferWriter(AttributeFileWriter &fileWriter)
     : AttributeFileBufferWriter(fileWriter)
-{
-}
-
-
-FileBackedBufferWriter::~FileBackedBufferWriter()
-{
-}
+{ }
 
+FileBackedBufferWriter::~FileBackedBufferWriter() = default;
 
 void
 FileBackedBufferWriter::onFlush(size_t nowLen) {
     // Note: Must use const ptr to indicate that buffer is pre-filled.
-    Buffer buf(std::make_unique<BufferBuf>
-               ((const char *) _buf->getFree(), nowLen));
+    auto buf(std::make_unique<BufferBuf>(static_cast<const void *>(_buf->getFree()), nowLen));
     assert(buf->getDataLen() == nowLen);
     assert(buf->getData() == _buf->getFree());
     _fileWriter.writeBuf(std::move(buf));
@@ -93,7 +83,6 @@ FileBackedBufferWriter::onFlush(size_t nowLen) {
 
 }
 
-
 AttributeFileWriter::
 AttributeFileWriter(const TuneFileAttributes &tuneFileAttributes,
                     const FileHeaderContext &fileHeaderContext,
@@ -107,9 +96,7 @@ AttributeFileWriter(const TuneFileAttributes &tuneFileAttributes,
       _fileBitSize(0)
 { }
 
-
-AttributeFileWriter::~AttributeFileWriter() { }
-
+AttributeFileWriter::~AttributeFileWriter() = default;
 
 bool
 AttributeFileWriter::open(const vespalib::string &fileName)
@@ -130,7 +117,6 @@ AttributeFileWriter::open(const vespalib::string &fileName)
     return true;
 }
 
-
 void
 AttributeFileWriter::writeHeader()
 {
@@ -142,7 +128,6 @@ AttributeFileWriter::writeHeader()
     _fileBitSize = headerLen * 8;
 }
 
-
 void
 AttributeFileWriter::addTags(vespalib::GenericHeader &header)
 {
@@ -151,14 +136,12 @@ AttributeFileWriter::addTags(vespalib::GenericHeader &header)
     header.putTag(Tag("desc", _desc));
 }
 
-
 AttributeFileWriter::Buffer
 AttributeFileWriter::allocBuf(size_t size)
 {
     return std::make_unique<BufferBuf>(size, MIN_ALIGNMENT);
 }
 
-
 void
 AttributeFileWriter::writeBuf(Buffer buf)
 {
@@ -168,7 +151,6 @@ AttributeFileWriter::writeBuf(Buffer buf)
     _fileBitSize += bufLen * 8;
 }
 
-
 void
 AttributeFileWriter::close()
 {
@@ -179,13 +161,10 @@ AttributeFileWriter::close()
     }
 }
 
-
 std::unique_ptr<BufferWriter>
 AttributeFileWriter::allocBufferWriter()
 {
     return std::make_unique<FileBackedBufferWriter>(*this);
 }
 
-
-
 } // namespace search
diff --git a/searchlib/src/vespa/searchlib/docstore/documentstore.cpp b/searchlib/src/vespa/searchlib/docstore/documentstore.cpp
index 59e92b112fa..a6c5f567454 100644
--- a/searchlib/src/vespa/searchlib/docstore/documentstore.cpp
+++ b/searchlib/src/vespa/searchlib/docstore/documentstore.cpp
@@ -35,8 +35,7 @@ void
 DocumentVisitorAdapter::visit(uint32_t lid, vespalib::ConstBufferRef buf) {
     if (buf.size() > 0) {
         vespalib::nbostream is(buf.c_str(), buf.size());
-        document::Document::UP doc(new document::Document(_repo, is));
-        _visitor.visit(lid, std::move(doc));
+        _visitor.visit(lid, std::make_unique<document::Document>(_repo, is));
     }
 }
 
@@ -51,34 +50,38 @@ public:
     using Alloc = vespalib::alloc::Alloc;
     typedef std::unique_ptr<Value> UP;
 
-    Value() : _compressedSize(0), _uncompressedSize(0), _compression(CompressionConfig::NONE) {}
-
-    Value(Value &&rhs) :
-            _compressedSize(rhs._compressedSize),
-            _uncompressedSize(rhs._uncompressedSize),
-            _compression(rhs._compression),
-            _buf(std::move(rhs._buf)) {}
-
-    Value(const Value &rhs) :
-            _compressedSize(rhs._compressedSize),
-            _uncompressedSize(rhs._uncompressedSize),
-            _compression(rhs._compression),
-            _buf(Alloc::alloc(rhs.size())) {
+    Value()
+        : _syncToken(0),
+          _compressedSize(0),
+          _uncompressedSize(0),
+          _compression(CompressionConfig::NONE)
+    {}
+
+    Value(uint64_t syncToken)
+        : _syncToken(syncToken),
+          _compressedSize(0),
+          _uncompressedSize(0),
+          _compression(CompressionConfig::NONE)
+    {}
+
+    Value(Value &&rhs) = default;
+    Value &operator=(Value &&rhs) = default;
+
+    Value(const Value &rhs)
+        : _syncToken(rhs._syncToken),
+          _compressedSize(rhs._compressedSize),
+          _uncompressedSize(rhs._uncompressedSize),
+          _compression(rhs._compression),
+          _buf(Alloc::alloc(rhs.size()))
+    {
         memcpy(get(), rhs.get(), size());
     }
 
-    Value &operator=(Value &&rhs) {
-        _buf = std::move(rhs._buf);
-        _compressedSize = rhs._compressedSize;
-        _uncompressedSize = rhs._uncompressedSize;
-        _compression = rhs._compression;
-        return *this;
-    }
-
     void setCompression(CompressionConfig::Type comp, size_t uncompressedSize) {
         _compression = comp;
         _uncompressedSize = uncompressedSize;
     }
+    uint64_t getSyncToken() const { return _syncToken; }
 
     CompressionConfig::Type getCompression() const { return _compression; }
 
@@ -96,7 +99,8 @@ public:
      * Decompress value into temporary buffer and deserialize document from
      * the temporary buffer.
      */
-    document::Document::UP deserializeDocument(const DocumentTypeRepo &repo);
+    document::Document::UP deserializeDocument(const DocumentTypeRepo &repo) const;
+    vespalib::DataBuffer decompressed() const;
 
     size_t size() const { return _compressedSize; }
     bool empty() const { return size() == 0; }
@@ -104,6 +108,7 @@ public:
     const void *get() const { return _buf.get(); }
     void *get() { return _buf.get(); }
 private:
+    uint64_t _syncToken;
     size_t _compressedSize;
     size_t _uncompressedSize;
     CompressionConfig::Type _compression;
@@ -119,7 +124,7 @@ public:
 
     bool read(DocumentIdT key, Value &value) const;
     void visit(const IDocumentStore::LidVector &lids, const DocumentTypeRepo &repo, IDocumentVisitor &visitor) const;
-    void write(DocumentIdT, const Value &) {}
+    void write(DocumentIdT, const Value &);
     void erase(DocumentIdT) {}
     const CompressionConfig &getCompression() const { return _compression; }
     void reconfigure(const CompressionConfig &compression);
@@ -138,8 +143,7 @@ void
 Value::set(vespalib::DataBuffer &&buf, ssize_t len, const CompressionConfig &compression) {
     //Underlying buffer must be identical to allow swap.
     vespalib::DataBuffer compressed(buf.getData(), 0u);
-    CompressionConfig::Type type = compress(compression, vespalib::ConstBufferRef(buf.getData(), len),
-                                            compressed, true);
+    CompressionConfig::Type type = compress(compression, vespalib::ConstBufferRef(buf.getData(), len), compressed, true);
     _compressedSize = compressed.getDataLen();
     if (buf.getData() == compressed.getData()) {
         // Uncompressed so we can just steal the underlying buffer.
@@ -154,16 +158,20 @@ Value::set(vespalib::DataBuffer &&buf, ssize_t len, const CompressionConfig &com
     setCompression(type, len);
 }
 
+vespalib::DataBuffer
+Value::decompressed() const {
+    vespalib::DataBuffer uncompressed(_buf.get(), (size_t) 0);
+    decompress(getCompression(), getUncompressedSize(), vespalib::ConstBufferRef(*this, size()), uncompressed, true);
+    return uncompressed;
+}
 
 document::Document::UP
-Value::deserializeDocument(const DocumentTypeRepo &repo) {
-    vespalib::DataBuffer uncompressed((char *) _buf.get(), (size_t) 0);
-    decompress(getCompression(), getUncompressedSize(), vespalib::ConstBufferRef(*this, size()), uncompressed, true);
+Value::deserializeDocument(const DocumentTypeRepo &repo) const {
+    vespalib::DataBuffer uncompressed(decompressed());
     vespalib::nbostream is(uncompressed.getData(), uncompressed.getDataLen());
-    return document::Document::UP(new document::Document(repo, is));
+    return std::make_unique<document::Document>(repo, is);
 }
 
-
 void
 BackingStore::visit(const IDocumentStore::LidVector &lids, const DocumentTypeRepo &repo,
                     IDocumentVisitor &visitor) const {
@@ -184,6 +192,14 @@ BackingStore::read(DocumentIdT key, Value &value) const {
 }
 
 void
+BackingStore::write(DocumentIdT lid, const Value & value)
+{
+    assert(value.getCompression() == _compression.type);
+    vespalib::DataBuffer buf = value.decompressed();
+    _backingStore.write(value.getSyncToken(), lid, buf.getData(), buf.getDataLen());
+}
+
+void
 BackingStore::reconfigure(const CompressionConfig &compression) {
     _compression = compression;
 }
@@ -194,8 +210,7 @@ using CacheParams = vespalib::CacheParam<
         vespalib::LruParam<DocumentIdT, docstore::Value>,
         docstore::BackingStore,
         vespalib::zero<DocumentIdT>,
-        vespalib::size<docstore::Value>
->;
+        vespalib::size<docstore::Value> >;
 
 class Cache : public vespalib::cache<CacheParams> {
 public:
@@ -210,6 +225,7 @@ DocumentStore::Config::operator == (const Config &rhs) const {
     return (_maxCacheBytes == rhs._maxCacheBytes) &&
             (_allowVisitCaching == rhs._allowVisitCaching) &&
             (_initialCacheEntries == rhs._initialCacheEntries) &&
+            (_updateStrategy == rhs._updateStrategy) &&
             (_compression == rhs._compression);
 }
 
@@ -226,7 +242,7 @@ DocumentStore::DocumentStore(const Config & config, IDataStore & store)
     _cache->reserveElements(config.getInitialCacheEntries());
 }
 
-DocumentStore::~DocumentStore() {}
+DocumentStore::~DocumentStore() = default;
 
 void
 DocumentStore::reconfigure(const Config & config) {
@@ -282,10 +298,22 @@ DocumentStore::write(uint64_t syncToken, DocumentIdT lid, const document::Docume
 
 void
 DocumentStore::write(uint64_t syncToken, DocumentIdT lid, const vespalib::nbostream & stream) {
-    _backingStore.write(syncToken, lid, stream.peek(), stream.size());
     if (useCache()) {
-        _cache->invalidate(lid);
-        _visitCache->invalidate(lid);
+        switch (_config.updateStrategy()) {
+            case Config::UpdateStrategy::INVALIDATE:
+                _backingStore.write(syncToken, lid, stream.peek(), stream.size());
+                _cache->invalidate(lid);
+                break;
+            case Config::UpdateStrategy::UPDATE: {
+                Value value(syncToken);
+                value.set(vespalib::DataBuffer(), stream.size(), _store->getCompression());
+                _cache->write(lid, std::move(value));
+                break;
+            }
+        }
+        _visitCache->invalidate(lid); // The cost and complexity of this updating this is not worth it.
+    } else {
+        _backingStore.write(syncToken, lid, stream.peek(), stream.size());
     }
 }
 
diff --git a/searchlib/src/vespa/searchlib/docstore/documentstore.h b/searchlib/src/vespa/searchlib/docstore/documentstore.h
index 08b042d99c5..7bc3ab1c21d 100644
--- a/searchlib/src/vespa/searchlib/docstore/documentstore.h
+++ b/searchlib/src/vespa/searchlib/docstore/documentstore.h
@@ -27,17 +27,20 @@ class DocumentStore : public IDocumentStore
 public:
     class Config {
     public:
+        enum UpdateStrategy {INVALIDATE, UPDATE };
         using CompressionConfig = vespalib::compression::CompressionConfig;
         Config() :
             _compression(CompressionConfig::LZ4, 9, 70),
             _maxCacheBytes(1000000000),
             _initialCacheEntries(0),
+            _updateStrategy(INVALIDATE),
             _allowVisitCaching(false)
         { }
         Config(const CompressionConfig & compression, size_t maxCacheBytes, size_t initialCacheEntries) :
             _compression((maxCacheBytes != 0) ? compression : CompressionConfig::NONE),
             _maxCacheBytes(maxCacheBytes),
             _initialCacheEntries(initialCacheEntries),
+            _updateStrategy(INVALIDATE),
             _allowVisitCaching(false)
         { }
         const CompressionConfig & getCompression() const { return _compression; }
@@ -45,11 +48,14 @@ public:
         size_t getInitialCacheEntries() const { return _initialCacheEntries; }
         bool allowVisitCaching() const { return _allowVisitCaching; }
         Config & allowVisitCaching(bool allow) { _allowVisitCaching = allow; return *this; }
+        Config & updateStrategy(UpdateStrategy strategy) { _updateStrategy = strategy; return *this; }
+        UpdateStrategy updateStrategy() const { return _updateStrategy; }
         bool operator == (const Config &) const;
     private:
         CompressionConfig _compression;
         size_t _maxCacheBytes;
         size_t _initialCacheEntries;
+        UpdateStrategy _updateStrategy;
         bool   _allowVisitCaching;
     };
 
@@ -82,14 +88,10 @@ public:
     CacheStats getCacheStats() const override;
     size_t memoryMeta() const override { return _backingStore.memoryMeta(); }
     const vespalib::string & getBaseDir() const override { return _backingStore.getBaseDir(); }
-    void
-    accept(IDocumentStoreReadVisitor &visitor,
-           IDocumentStoreVisitorProgress &visitorProgress,
-           const document::DocumentTypeRepo &repo) override;
-    void
-    accept(IDocumentStoreRewriteVisitor &visitor,
-           IDocumentStoreVisitorProgress &visitorProgress,
-           const document::DocumentTypeRepo &repo) override;
+    void accept(IDocumentStoreReadVisitor &visitor, IDocumentStoreVisitorProgress &visitorProgress,
+                const document::DocumentTypeRepo &repo) override;
+    void accept(IDocumentStoreRewriteVisitor &visitor, IDocumentStoreVisitorProgress &visitorProgress,
+                const document::DocumentTypeRepo &repo) override;
     double getVisitCost() const override;
     DataStoreStorageStats getStorageStats() const override;
     MemoryUsage getMemoryUsage() const override;
diff --git a/searchlib/src/vespa/searchlib/docstore/logdocumentstore.cpp b/searchlib/src/vespa/searchlib/docstore/logdocumentstore.cpp
index e2b29f6bdd6..c285d4323c2 100644
--- a/searchlib/src/vespa/searchlib/docstore/logdocumentstore.cpp
+++ b/searchlib/src/vespa/searchlib/docstore/logdocumentstore.cpp
@@ -26,7 +26,7 @@ LogDocumentStore::LogDocumentStore(vespalib::ThreadExecutor & executor,
                     tuneFileSummary, fileHeaderContext, tlSyncer, bucketizer)
 {}
 
-LogDocumentStore::~LogDocumentStore() {}
+LogDocumentStore::~LogDocumentStore() = default;
 
 void
 LogDocumentStore::reconfigure(const Config & config) {