Clang: Minimize reindexing

We optimal indexer is only reindexing if the index would be changed. This
patch is a step in that direction. We only reindex now if the file or
project has changed. It fixes some typos too.

Task-number: QTCREATORBUG-21150
Change-Id: I6ea1c13282fbcd70253b9b2939aed37580dbd160
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

37 files changed, 736 insertions, 120 deletions

diff --git a/src/libs/clangsupport/clangsupport-lib.pri b/src/libs/clangsupport/clangsupport-lib.pri
index 0668382803..086755d5dc 100644
--- a/src/libs/clangsupport/clangsupport-lib.pri
+++ b/src/libs/clangsupport/clangsupport-lib.pri
@@ -213,6 +213,9 @@ HEADERS += \
     $$PWD/includesearchpath.h \
     $$PWD/commandlinebuilder.h \
     $$PWD/projectpartartefact.h \
-    $$PWD/projectpartcontainer.h
+    $$PWD/projectpartcontainer.h \
+    $$PWD/sourceentry.h \
+    $$PWD/modifiedtimecheckerinterface.h \
+    $$PWD/modifiedtimechecker.h
 
 contains(QT_CONFIG, reduce_exports):CONFIG += hide_symbols
diff --git a/src/tools/clangpchmanagerbackend/source/modifiedtimechecker.h b/src/libs/clangsupport/modifiedtimechecker.h
index d641de054c..c9b62c4673 100644
--- a/src/tools/clangpchmanagerbackend/source/modifiedtimechecker.h
+++ b/src/libs/clangsupport/modifiedtimechecker.h
@@ -25,17 +25,18 @@
 
 #pragma once
 
+#include "filepathcachinginterface.h"
 #include "modifiedtimecheckerinterface.h"
 
-#include <filepathcachinginterface.h>
-
 #include <algorithm>
 #include <iterator>
 
 namespace ClangBackEnd {
-
-class ModifiedTimeChecker final : public ModifiedTimeCheckerInterface
+template<typename SourceEntries = ::ClangBackEnd::SourceEntries>
+class ModifiedTimeChecker final : public ModifiedTimeCheckerInterface<SourceEntries>
 {
+    using SourceEntry = typename SourceEntries::value_type;
+
 public:
     using GetModifiedTime = std::function<ClangBackEnd::TimeStamp(ClangBackEnd::FilePathView filePath)>;
     ModifiedTimeChecker(GetModifiedTime &getModifiedTime, FilePathCachingInterface &filePathCache)
@@ -67,7 +68,7 @@ public:
                               std::back_inserter(timeStampsToUpdate));
 
         for (SourceTimeStamp &sourceTimeStamp : timeStampsToUpdate) {
-            sourceTimeStamp.lastModified = m_getModifiedTime(
+            sourceTimeStamp.timeStamp = m_getModifiedTime(
                 m_filePathCache.filePath(sourceTimeStamp.sourceId));
         }
     }
@@ -78,21 +79,22 @@ private:
         class CompareSourceId
         {
         public:
-            bool operator()(SourceTimeStamp first, SourceTimeStamp second) {
+            bool operator()(SourceTimeStamp first, SourceTimeStamp second)
+            {
                 return first.sourceId < second.sourceId;
             }
 
-            bool operator()(SourceEntry first, SourceEntry second)
+            bool operator()(::ClangBackEnd::SourceEntry first, ::ClangBackEnd::SourceEntry second)
             {
                 return first.sourceId < second.sourceId;
             }
 
-            bool operator()(SourceTimeStamp first, SourceEntry second)
+            bool operator()(SourceTimeStamp first, ::ClangBackEnd::SourceEntry second)
             {
                 return first.sourceId < second.sourceId;
             }
 
-            bool operator()(SourceEntry first, SourceTimeStamp second)
+            bool operator()(::ClangBackEnd::SourceEntry first, SourceTimeStamp second)
             {
                 return first.sourceId < second.sourceId;
             }
@@ -112,23 +114,22 @@ private:
         public:
             bool operator()(SourceTimeStamp first, SourceTimeStamp second)
             {
-                return first.lastModified <= second.lastModified;
+                return first.timeStamp <= second.timeStamp;
             }
 
-            bool operator()(SourceEntry first, SourceEntry second)
+            bool operator()(::ClangBackEnd::SourceEntry first, ::ClangBackEnd::SourceEntry second)
             {
-                return first.pchCreationTimeStamp <=
-                    second.pchCreationTimeStamp;
+                return first.timeStamp <= second.timeStamp;
             }
 
-            bool operator()(SourceTimeStamp first, SourceEntry second)
+            bool operator()(SourceTimeStamp first, ::ClangBackEnd::SourceEntry second)
             {
-                return first.lastModified <= second.pchCreationTimeStamp;
+                return first.timeStamp <= second.timeStamp;
             }
 
-            bool operator()(SourceEntry first, SourceTimeStamp second)
+            bool operator()(::ClangBackEnd::SourceEntry first, SourceTimeStamp second)
             {
-                return first.pchCreationTimeStamp <= second.lastModified;
+                return first.timeStamp <= second.timeStamp;
             }
         };
 
@@ -144,7 +145,7 @@ private:
         SourceTimeStamps sourceTimeStamps = newSourceTimeStamps(sourceEntries);
 
         for (SourceTimeStamp &newSourceTimeStamp : sourceTimeStamps) {
-            newSourceTimeStamp.lastModified = m_getModifiedTime(
+            newSourceTimeStamp.timeStamp = m_getModifiedTime(
                 m_filePathCache.filePath(newSourceTimeStamp.sourceId));
         }
 
@@ -169,17 +170,17 @@ private:
                 return first.sourceId < second.sourceId;
             }
 
-            bool operator()(SourceEntry first, SourceEntry second)
+            bool operator()(::ClangBackEnd::SourceEntry first, ::ClangBackEnd::SourceEntry second)
             {
                 return first.sourceId < second.sourceId;
             }
 
-            bool operator()(SourceTimeStamp first, SourceEntry second)
+            bool operator()(SourceTimeStamp first, ::ClangBackEnd::SourceEntry second)
             {
                 return first.sourceId < second.sourceId;
             }
 
-            bool operator()(SourceEntry first, SourceTimeStamp second)
+            bool operator()(::ClangBackEnd::SourceEntry first, SourceTimeStamp second)
             {
                 return first.sourceId < second.sourceId;
             }
diff --git a/src/tools/clangpchmanagerbackend/source/modifiedtimecheckerinterface.h b/src/libs/clangsupport/modifiedtimecheckerinterface.h
index c0cae1cf4b..a0e79b0701 100644
--- a/src/tools/clangpchmanagerbackend/source/modifiedtimecheckerinterface.h
+++ b/src/libs/clangsupport/modifiedtimecheckerinterface.h
@@ -29,6 +29,7 @@
 
 namespace ClangBackEnd {
 
+template<typename SourceEntries = ::ClangBackEnd::SourceEntries>
 class ModifiedTimeCheckerInterface
 {
 public:
diff --git a/src/libs/clangsupport/projectpartsstorage.h b/src/libs/clangsupport/projectpartsstorage.h
index 4e29cee03e..e54a7a61d1 100644
--- a/src/libs/clangsupport/projectpartsstorage.h
+++ b/src/libs/clangsupport/projectpartsstorage.h
@@ -245,6 +245,22 @@ public:
         return statement.template value<ProjectPartArtefact, 8>(projectPartId.projectPathId);
     }
 
+    void resetIndexingTimeStamps(const ProjectPartContainers &projectsParts) override
+    {
+        try {
+            Sqlite::ImmediateTransaction transaction{database};
+
+            for (const ProjectPartContainer &projectPart : projectsParts) {
+                for (FilePathId sourcePathId : projectPart.sourcePathIds)
+                    resetDependentIndexingTimeStampsStatement.write(sourcePathId.filePathId);
+            }
+
+            transaction.commit();
+        } catch (const Sqlite::StatementIsBusy &) {
+            resetIndexingTimeStamps(projectsParts);
+        }
+    }
+
     Sqlite::TransactionInterface &transactionBackend() override { return database; }
 
     static Utils::SmallString toJson(const Utils::SmallStringVector &strings)
@@ -343,5 +359,11 @@ public:
         "SELECT sourceId FROM projectPartsSources WHERE projectPartId = ?", database};
     mutable ReadStatement fetchProjectPrecompiledHeaderPathStatement{
         "SELECT projectPchPath FROM precompiledHeaders WHERE projectPartId = ?", database};
+    WriteStatement resetDependentIndexingTimeStampsStatement{
+        "WITH RECURSIVE collectedDependencies(sourceId) AS (VALUES(?) UNION SELECT "
+        "dependencySourceId FROM sourceDependencies, collectedDependencies WHERE "
+        "sourceDependencies.sourceId == collectedDependencies.sourceId) UPDATE fileStatuses SET "
+        "indexingTimeStamp = NULL WHERE sourceId IN (SELECT sourceId FROM collectedDependencies)",
+        database};
 };
 } // namespace ClangBackEnd
diff --git a/src/libs/clangsupport/projectpartsstorageinterface.h b/src/libs/clangsupport/projectpartsstorageinterface.h
index 1127f70b1f..2d0675e657 100644
--- a/src/libs/clangsupport/projectpartsstorageinterface.h
+++ b/src/libs/clangsupport/projectpartsstorageinterface.h
@@ -63,6 +63,7 @@ public:
     virtual Utils::optional<ProjectPartArtefact> fetchProjectPartArtefact(FilePathId sourceId) const = 0;
     virtual Utils::optional<ProjectPartArtefact> fetchProjectPartArtefact(
         ProjectPartId projectPartId) const = 0;
+    virtual void resetIndexingTimeStamps(const ProjectPartContainers &projectsParts) = 0;
 
     virtual Sqlite::TransactionInterface &transactionBackend() = 0;
 
diff --git a/src/libs/clangsupport/refactoringdatabaseinitializer.h b/src/libs/clangsupport/refactoringdatabaseinitializer.h
index efca925413..a7058d3204 100644
--- a/src/libs/clangsupport/refactoringdatabaseinitializer.h
+++ b/src/libs/clangsupport/refactoringdatabaseinitializer.h
@@ -177,6 +177,7 @@ public:
                         Sqlite::Contraint::PrimaryKey);
         table.addColumn("size", Sqlite::ColumnType::Integer);
         table.addColumn("lastModified", Sqlite::ColumnType::Integer);
+        table.addColumn("indexingTimeStamp", Sqlite::ColumnType::Integer);
         table.initialize(database);
     }
 
@@ -188,6 +189,7 @@ public:
         const Sqlite::Column &sourceIdColumn = table.addColumn("sourceId", Sqlite::ColumnType::Integer);
         const Sqlite::Column &dependencySourceIdColumn = table.addColumn("dependencySourceId", Sqlite::ColumnType::Integer);
         table.addIndex({sourceIdColumn, dependencySourceIdColumn});
+        table.addIndex({dependencySourceIdColumn, sourceIdColumn});
 
         table.initialize(database);
     }
diff --git a/src/tools/clangpchmanagerbackend/source/sourceentry.h b/src/libs/clangsupport/sourceentry.h
index 5c45db6bde..c593f1fcd3 100644
--- a/src/tools/clangpchmanagerbackend/source/sourceentry.h
+++ b/src/libs/clangsupport/sourceentry.h
@@ -64,12 +64,12 @@ class SourceTimeStamp
     using int64 = long long;
 public:
     SourceTimeStamp(int sourceId, int64 lastModified)
-        : lastModified(lastModified)
+        : timeStamp(lastModified)
         , sourceId(sourceId)
     {}
 
     SourceTimeStamp(FilePathId sourceId, TimeStamp lastModified)
-        : lastModified(lastModified)
+        : timeStamp(lastModified)
         , sourceId(sourceId)
     {}
 
@@ -90,7 +90,7 @@ public:
 
     friend bool operator==(SourceTimeStamp first, SourceTimeStamp second)
     {
-        return first.sourceId == second.sourceId && first.lastModified == second.lastModified;
+        return first.sourceId == second.sourceId && first.timeStamp == second.timeStamp;
     }
 
     friend bool operator!=(SourceTimeStamp first, SourceTimeStamp second)
@@ -99,7 +99,7 @@ public:
     }
 
 public:
-    TimeStamp lastModified;
+    TimeStamp timeStamp;
     FilePathId sourceId;
 };
 
@@ -110,21 +110,22 @@ class SourceEntry
     using int64 = long long;
 
 public:
-    SourceEntry(int sourceId,
-                int64 pchCreationTimeStamp,
-                int sourceType,
-                int hasMissingIncludes)
-        : pchCreationTimeStamp(pchCreationTimeStamp), sourceId(sourceId),
-          sourceType(static_cast<SourceType>(sourceType)),
-          hasMissingIncludes(
-              static_cast<HasMissingIncludes>(hasMissingIncludes)) {}
+    SourceEntry(int sourceId, int64 timeStamp, int sourceType, int hasMissingIncludes)
+        : timeStamp(timeStamp)
+        , sourceId(sourceId)
+        , sourceType(static_cast<SourceType>(sourceType))
+        , hasMissingIncludes(static_cast<HasMissingIncludes>(hasMissingIncludes))
+    {}
 
     SourceEntry(FilePathId sourceId,
                 SourceType sourceType,
-                TimeStamp pchCreationTimeStamp,
+                TimeStamp timeStamp,
                 HasMissingIncludes hasMissingIncludes = HasMissingIncludes::No)
-        : pchCreationTimeStamp(pchCreationTimeStamp), sourceId(sourceId),
-          sourceType(sourceType), hasMissingIncludes(hasMissingIncludes) {}
+        : timeStamp(timeStamp)
+        , sourceId(sourceId)
+        , sourceType(sourceType)
+        , hasMissingIncludes(hasMissingIncludes)
+    {}
 
     friend bool operator<(SourceEntry first, SourceEntry second) {
         return first.sourceId < second.sourceId;
@@ -133,13 +134,13 @@ public:
     friend bool operator==(SourceEntry first, SourceEntry second)
     {
         return first.sourceId == second.sourceId && first.sourceType == second.sourceType
-               && first.pchCreationTimeStamp == second.pchCreationTimeStamp;
+               && first.timeStamp == second.timeStamp;
     }
 
     friend bool operator!=(SourceEntry first, SourceEntry second) { return !(first == second); }
 
 public:
-    TimeStamp pchCreationTimeStamp;
+    TimeStamp timeStamp;
     FilePathId sourceId;
     SourceType sourceType = SourceType::UserInclude;
     HasMissingIncludes hasMissingIncludes = HasMissingIncludes::No;
diff --git a/src/plugins/clangcodemodel/clangcompletionchunkstotextconverter.cpp b/src/plugins/clangcodemodel/clangcompletionchunkstotextconverter.cpp
index 5af48386bd..ad5ee50476 100644
--- a/src/plugins/clangcodemodel/clangcompletionchunkstotextconverter.cpp
+++ b/src/plugins/clangcodemodel/clangcompletionchunkstotextconverter.cpp
@@ -47,7 +47,7 @@ void CompletionChunksToTextConverter::parseChunks(
                   m_codeCompletionChunks.cend(),
                   [this] (const ClangBackEnd::CodeCompletionChunk &chunk)
     {
-        parseDependendOnTheOptionalState(chunk);
+        parseDependentOnTheOptionalState(chunk);
         m_previousCodeCompletionChunk = chunk;
     });
 }
@@ -200,7 +200,7 @@ void CompletionChunksToTextConverter::parse(
     }
 }
 
-void CompletionChunksToTextConverter::parseDependendOnTheOptionalState(
+void CompletionChunksToTextConverter::parseDependentOnTheOptionalState(
         const ClangBackEnd::CodeCompletionChunk &codeCompletionChunk)
 {
     wrapInCursiveTagIfOptional(codeCompletionChunk);
diff --git a/src/plugins/clangcodemodel/clangcompletionchunkstotextconverter.h b/src/plugins/clangcodemodel/clangcompletionchunkstotextconverter.h
index 88654ed3fd..09ad15e30f 100644
--- a/src/plugins/clangcodemodel/clangcompletionchunkstotextconverter.h
+++ b/src/plugins/clangcodemodel/clangcompletionchunkstotextconverter.h
@@ -75,7 +75,7 @@ public:
 
 private:
     void parse(const ClangBackEnd::CodeCompletionChunk &codeCompletionChunk);
-    void parseDependendOnTheOptionalState(const ClangBackEnd::CodeCompletionChunk &codeCompletionChunk);
+    void parseDependentOnTheOptionalState(const ClangBackEnd::CodeCompletionChunk &codeCompletionChunk);
     void parseResultType(const Utf8String &text);
     void parseText(const Utf8String &text);
     void wrapInCursiveTagIfOptional(const ClangBackEnd::CodeCompletionChunk &codeCompletionChunk);
diff --git a/src/plugins/cpptools/compileroptionsbuilder.cpp b/src/plugins/cpptools/compileroptionsbuilder.cpp
index 8dfe0c7977..a1e01911d6 100644
--- a/src/plugins/cpptools/compileroptionsbuilder.cpp
+++ b/src/plugins/cpptools/compileroptionsbuilder.cpp
@@ -455,6 +455,8 @@ void CompilerOptionsBuilder::addLanguageVersionAndExtensions()
     case LanguageVersion::CXX2a:
         option = (gnuExtensions ? QLatin1String("-std=gnu++2a") : QLatin1String("-std=c++2a"));
         break;
+    case LanguageVersion::None:
+        break;
     }
 
     add(option, /*gccOnlyOption=*/true);
diff --git a/src/tools/clangpchmanagerbackend/clangpchmanagerbackendmain.cpp b/src/tools/clangpchmanagerbackend/clangpchmanagerbackendmain.cpp
index dc1c7085e7..a7ca916f15 100644
--- a/src/tools/clangpchmanagerbackend/clangpchmanagerbackendmain.cpp
+++ b/src/tools/clangpchmanagerbackend/clangpchmanagerbackendmain.cpp
@@ -215,7 +215,8 @@ struct Data // because we have a cycle dependency
         [&](ClangBackEnd::FilePathView path) -> TimeStamp {
             return QFileInfo(QString(path)).lastModified().toSecsSinceEpoch();
         }};
-    ClangBackEnd::ModifiedTimeChecker modifiedTimeChecker{getModifiedTime, filePathCache};
+    ClangBackEnd::ModifiedTimeChecker<ClangBackEnd::SourceEntries> modifiedTimeChecker{getModifiedTime,
+                                                                                       filePathCache};
     ClangBackEnd::BuildDependenciesProvider buildDependencyProvider{buildDependencyStorage,
                                                                     modifiedTimeChecker,
                                                                     buildDependencyCollector,
diff --git a/src/tools/clangpchmanagerbackend/source/builddependenciesprovider.h b/src/tools/clangpchmanagerbackend/source/builddependenciesprovider.h
index 9700b83aa3..a006b10a06 100644
--- a/src/tools/clangpchmanagerbackend/source/builddependenciesprovider.h
+++ b/src/tools/clangpchmanagerbackend/source/builddependenciesprovider.h
@@ -27,6 +27,8 @@
 
 #include "builddependenciesproviderinterface.h"
 
+#include <modifiedtimecheckerinterface.h>
+
 namespace Sqlite {
 class TransactionInterface;
 }
@@ -34,14 +36,13 @@ class TransactionInterface;
 namespace ClangBackEnd {
 
 class BuildDependenciesStorageInterface;
-class ModifiedTimeCheckerInterface;
 class BuildDependencyGeneratorInterface;
 
 class BuildDependenciesProvider : public BuildDependenciesProviderInterface
 {
 public:
     BuildDependenciesProvider(BuildDependenciesStorageInterface &buildDependenciesStorage,
-                              ModifiedTimeCheckerInterface &modifiedTimeChecker,
+                              ModifiedTimeCheckerInterface<> &modifiedTimeChecker,
                               BuildDependencyGeneratorInterface &buildDependenciesGenerator,
                               Sqlite::TransactionInterface &transactionBackend)
         : m_storage(buildDependenciesStorage)
@@ -61,7 +62,7 @@ private:
 
 private:
     BuildDependenciesStorageInterface &m_storage;
-    ModifiedTimeCheckerInterface &m_modifiedTimeChecker;
+    ModifiedTimeCheckerInterface<> &m_modifiedTimeChecker;
     BuildDependencyGeneratorInterface &m_generator;
     Sqlite::TransactionInterface &m_transactionBackend;
 };
diff --git a/src/tools/clangpchmanagerbackend/source/clangpchmanagerbackend-source.pri b/src/tools/clangpchmanagerbackend/source/clangpchmanagerbackend-source.pri
index 61bcedc262..bbf3bf16f4 100644
--- a/src/tools/clangpchmanagerbackend/source/clangpchmanagerbackend-source.pri
+++ b/src/tools/clangpchmanagerbackend/source/clangpchmanagerbackend-source.pri
@@ -29,8 +29,6 @@ HEADERS += \
     $$PWD/builddependenciesprovider.h \
     $$PWD/builddependenciesstorageinterface.h \
     $$PWD/builddependency.h \
-    $$PWD/modifiedtimecheckerinterface.h \
-    $$PWD/sourceentry.h \
     $$PWD/builddependenciesstorage.h \
     $$PWD/builddependencygeneratorinterface.h \
     $$PWD/usedmacrofilter.h \
@@ -40,8 +38,7 @@ HEADERS += \
     $$PWD/pchtaskqueue.h \
     $$PWD/generatepchactionfactory.h \
     $$PWD/pchtaskgeneratorinterface.h \
-    $$PWD/toolchainargumentscache.h \
-    $$PWD/modifiedtimechecker.h
+    $$PWD/toolchainargumentscache.h
 
 !isEmpty(LIBTOOLING_LIBS) {
 SOURCES += \
diff --git a/src/tools/clangpchmanagerbackend/source/collectbuilddependencypreprocessorcallbacks.h b/src/tools/clangpchmanagerbackend/source/collectbuilddependencypreprocessorcallbacks.h
index f3b365d8d5..9db095bd75 100644
--- a/src/tools/clangpchmanagerbackend/source/collectbuilddependencypreprocessorcallbacks.h
+++ b/src/tools/clangpchmanagerbackend/source/collectbuilddependencypreprocessorcallbacks.h
@@ -293,7 +293,7 @@ public:
             entry.get().hasMissingIncludes = HasMissingIncludes::Yes;
     }
 
-    SourceDependencies sourceDependenciesSortedByDependendFilePathId() const
+    SourceDependencies sourceDependenciesSortedByDependentFilePathId() const
     {
         auto sourceDependencies = m_buildDependency.sourceDependencies;
         std::sort(sourceDependencies.begin(), sourceDependencies.end(), [](auto first, auto second) {
@@ -309,7 +309,7 @@ public:
         sortAndMakeUnique(m_containsMissingIncludes);
 
         collectSourceWithMissingIncludes(m_containsMissingIncludes,
-                                         sourceDependenciesSortedByDependendFilePathId());
+                                         sourceDependenciesSortedByDependentFilePathId());
 
         removeSourceWithMissingIncludesFromSources();
     }
diff --git a/src/tools/clangpchmanagerbackend/source/projectpartsmanager.cpp b/src/tools/clangpchmanagerbackend/source/projectpartsmanager.cpp
index 584d06ded2..cc4ca53d7d 100644
--- a/src/tools/clangpchmanagerbackend/source/projectpartsmanager.cpp
+++ b/src/tools/clangpchmanagerbackend/source/projectpartsmanager.cpp
@@ -65,7 +65,7 @@ ProjectPartContainers ProjectPartsManager::update(ProjectPartContainers &&projec
     }
 
     m_projectPartsStorage.updateProjectParts(updatedProjectParts);
-
+    m_projectPartsStorage.resetIndexingTimeStamps(updatedProjectParts);
     m_precompiledHeaderStorage.deleteProjectPrecompiledHeaders(
         toProjectPartIds(updatedProjectParts));
 
diff --git a/src/tools/clangrefactoringbackend/source/symbolindexer.cpp b/src/tools/clangrefactoringbackend/source/symbolindexer.cpp
index e21268322a..6d0978e54a 100644
--- a/src/tools/clangrefactoringbackend/source/symbolindexer.cpp
+++ b/src/tools/clangrefactoringbackend/source/symbolindexer.cpp
@@ -66,7 +66,8 @@ SymbolIndexer::SymbolIndexer(SymbolIndexerTaskQueueInterface &symbolIndexerTaskQ
                              FilePathCachingInterface &filePathCache,
                              FileStatusCache &fileStatusCache,
                              Sqlite::TransactionInterface &transactionInterface,
-                             ProjectPartsStorageInterface &projectPartsStorage)
+                             ProjectPartsStorageInterface &projectPartsStorage,
+                             ModifiedTimeCheckerInterface<SourceTimeStamps> &modifiedTimeChecker)
     : m_symbolIndexerTaskQueue(symbolIndexerTaskQueue)
     , m_symbolStorage(symbolStorage)
     , m_buildDependencyStorage(buildDependenciesStorage)
@@ -76,6 +77,7 @@ SymbolIndexer::SymbolIndexer(SymbolIndexerTaskQueueInterface &symbolIndexerTaskQ
     , m_fileStatusCache(fileStatusCache)
     , m_transactionInterface(transactionInterface)
     , m_projectPartsStorage(projectPartsStorage)
+    , m_modifiedTimeChecker(modifiedTimeChecker)
 {
     pathWatcher.setNotifier(this);
 }
@@ -109,23 +111,27 @@ void SymbolIndexer::updateProjectPart(ProjectPartContainer &&projectPart)
     std::vector<SymbolIndexerTask> symbolIndexerTask;
     symbolIndexerTask.reserve(projectPart.sourcePathIds.size());
     for (FilePathId sourcePathId : projectPart.sourcePathIds) {
-        auto indexing = [arguments = commandLineBuilder.commandLine,
-                         sourcePathId,
-                         this](SymbolsCollectorInterface &symbolsCollector) {
-            symbolsCollector.setFile(sourcePathId, arguments);
-
-            bool success = symbolsCollector.collectSymbols();
-
-            if (success) {
-                Sqlite::ImmediateTransaction transaction{m_transactionInterface};
-
-                m_symbolStorage.addSymbolsAndSourceLocations(symbolsCollector.symbols(),
-                                                             symbolsCollector.sourceLocations());
-                transaction.commit();
-            }
-        };
-
-        symbolIndexerTask.emplace_back(sourcePathId, projectPartId, std::move(indexing));
+        SourceTimeStamps dependentTimeStamps = m_symbolStorage.fetchIncludedIndexingTimeStamps(
+            sourcePathId);
+
+        if (!m_modifiedTimeChecker.isUpToDate(dependentTimeStamps)) {
+            auto indexing = [arguments = commandLineBuilder.commandLine, sourcePathId, this](
+                                SymbolsCollectorInterface &symbolsCollector) {
+                symbolsCollector.setFile(sourcePathId, arguments);
+
+                bool success = symbolsCollector.collectSymbols();
+
+                if (success) {
+                    Sqlite::ImmediateTransaction transaction{m_transactionInterface};
+                    m_symbolStorage.insertOrUpdateIndexingTimeStamps(symbolsCollector.fileStatuses());
+                    m_symbolStorage.addSymbolsAndSourceLocations(symbolsCollector.symbols(),
+                                                                 symbolsCollector.sourceLocations());
+                    transaction.commit();
+                }
+            };
+
+            symbolIndexerTask.emplace_back(sourcePathId, projectPartId, std::move(indexing));
+        }
     }
 
     m_symbolIndexerTaskQueue.addOrUpdateTasks(std::move(symbolIndexerTask));
@@ -136,11 +142,13 @@ void SymbolIndexer::pathsWithIdsChanged(const ProjectPartIds &) {}
 
 void SymbolIndexer::pathsChanged(const FilePathIds &filePathIds)
 {
+    FilePathIds dependentSourcePathIds = m_symbolStorage.fetchDependentSourceIds(filePathIds);
+
     std::vector<SymbolIndexerTask> symbolIndexerTask;
-    symbolIndexerTask.reserve(filePathIds.size());
+    symbolIndexerTask.reserve(dependentSourcePathIds.size());
 
-    for (FilePathId filePathId : filePathIds)
-        updateChangedPath(filePathId, symbolIndexerTask);
+    for (FilePathId dependentSourcePathId : dependentSourcePathIds)
+        updateChangedPath(dependentSourcePathId, symbolIndexerTask);
 
     m_symbolIndexerTaskQueue.addOrUpdateTasks(std::move(symbolIndexerTask));
     m_symbolIndexerTaskQueue.processEntries();
@@ -161,6 +169,8 @@ void SymbolIndexer::updateChangedPath(FilePathId filePathId,
         = m_precompiledHeaderStorage.fetchPrecompiledHeader(optionalArtefact->projectPartId);
     transaction.commit();
 
+    SourceTimeStamps dependentTimeStamps = m_symbolStorage.fetchIncludedIndexingTimeStamps(filePathId);
+
     const ProjectPartArtefact &artefact = *optionalArtefact;
 
     auto pchPath = optionalProjectPartPch ? optionalProjectPartPch->pchPath : FilePath{};
@@ -176,10 +186,9 @@ void SymbolIndexer::updateChangedPath(FilePathId filePathId,
 
         if (success) {
             Sqlite::ImmediateTransaction transaction{m_transactionInterface};
-
+            m_symbolStorage.insertOrUpdateIndexingTimeStamps(symbolsCollector.fileStatuses());
             m_symbolStorage.addSymbolsAndSourceLocations(symbolsCollector.symbols(),
                                                          symbolsCollector.sourceLocations());
-
             transaction.commit();
         }
     };
diff --git a/src/tools/clangrefactoringbackend/source/symbolindexer.h b/src/tools/clangrefactoringbackend/source/symbolindexer.h
index c398c0f2bf..d574d0e01d 100644
--- a/src/tools/clangrefactoringbackend/source/symbolindexer.h
+++ b/src/tools/clangrefactoringbackend/source/symbolindexer.h
@@ -32,6 +32,7 @@
 #include "clangpathwatcher.h"
 
 #include <filecontainerv2.h>
+#include <modifiedtimecheckerinterface.h>
 #include <precompiledheaderstorageinterface.h>
 #include <projectpartcontainer.h>
 #include <projectpartsstorageinterface.h>
@@ -51,7 +52,8 @@ public:
                   FilePathCachingInterface &filePathCache,
                   FileStatusCache &fileStatusCache,
                   Sqlite::TransactionInterface &transactionInterface,
-                  ProjectPartsStorageInterface &projectPartsStorage);
+                  ProjectPartsStorageInterface &projectPartsStorage,
+                  ModifiedTimeCheckerInterface<SourceTimeStamps> &modifiedTimeChecker);
 
     void updateProjectParts(ProjectPartContainers &&projectParts);
     void updateProjectPart(ProjectPartContainer &&projectPart);
@@ -81,6 +83,7 @@ private:
     FileStatusCache &m_fileStatusCache;
     Sqlite::TransactionInterface &m_transactionInterface;
     ProjectPartsStorageInterface &m_projectPartsStorage;
+    ModifiedTimeCheckerInterface<SourceTimeStamps> &m_modifiedTimeChecker;
 };
 
 } // namespace ClangBackEnd
diff --git a/src/tools/clangrefactoringbackend/source/symbolindexing.h b/src/tools/clangrefactoringbackend/source/symbolindexing.h
index c942059bad..10df4e397b 100644
--- a/src/tools/clangrefactoringbackend/source/symbolindexing.h
+++ b/src/tools/clangrefactoringbackend/source/symbolindexing.h
@@ -38,13 +38,16 @@
 #include <precompiledheaderstorage.h>
 #include <projectpartsstorage.h>
 
-#include <refactoringdatabaseinitializer.h>
 #include <filepathcachingfwd.h>
+#include <modifiedtimechecker.h>
+#include <refactoringdatabaseinitializer.h>
 
 #include <sqlitedatabase.h>
 #include <sqlitereadstatement.h>
 #include <sqlitewritestatement.h>
 
+#include <QDateTime>
+#include <QFileInfo>
 #include <QFileSystemWatcher>
 
 #include <thread>
@@ -130,6 +133,12 @@ private:
     FileStatusCache m_fileStatusCache{m_filePathCache};
     SymbolsCollectorManager m_collectorManger;
     ProgressCounter m_progressCounter;
+    std::function<TimeStamp(FilePathView filePath)> getModifiedTime{
+        [&](ClangBackEnd::FilePathView path) -> TimeStamp {
+            return QFileInfo(QString(path)).lastModified().toSecsSinceEpoch();
+        }};
+    ModifiedTimeChecker<ClangBackEnd::SourceTimeStamps> m_modifiedTimeChecker{getModifiedTime,
+                                                                              m_filePathCache};
     SymbolIndexer m_indexer{m_indexerQueue,
                             m_symbolStorage,
                             m_buildDependencyStorage,
@@ -138,7 +147,8 @@ private:
                             m_filePathCache,
                             m_fileStatusCache,
                             m_symbolStorage.database,
-                            m_projectPartsStorage};
+                            m_projectPartsStorage,
+                            m_modifiedTimeChecker};
     SymbolIndexerTaskQueue m_indexerQueue{m_indexerScheduler, m_progressCounter};
     SymbolIndexerTaskScheduler m_indexerScheduler;
 };
diff --git a/src/tools/clangrefactoringbackend/source/symbolstorage.h b/src/tools/clangrefactoringbackend/source/symbolstorage.h
index 9dffe48c96..f21b0412b8 100644
--- a/src/tools/clangrefactoringbackend/source/symbolstorage.h
+++ b/src/tools/clangrefactoringbackend/source/symbolstorage.h
@@ -41,7 +41,7 @@
 
 namespace ClangBackEnd {
 
-template <typename DatabaseType>
+template<typename DatabaseType = Sqlite::Database>
 class SymbolStorage final : public SymbolStorageInterface
 {
     using Database = DatabaseType;
@@ -70,6 +70,93 @@ public:
         deleteNewLocationsTable();
     }
 
+    void insertOrUpdateIndexingTimeStamps(const FilePathIds &filePathIds, TimeStamp indexingTimeStamp)
+    {
+        try {
+            Sqlite::ImmediateTransaction transaction{database};
+
+            for (FilePathId filePathId : filePathIds) {
+                inserOrUpdateIndexingTimesStampStatement.write(filePathId.filePathId,
+                                                               indexingTimeStamp.value);
+            }
+
+            transaction.commit();
+        } catch (const Sqlite::StatementIsBusy &) {
+            insertOrUpdateIndexingTimeStamps(filePathIds, indexingTimeStamp);
+        }
+    }
+
+    void insertOrUpdateIndexingTimeStamps(const FileStatuses &fileStatuses) override
+    {
+        for (FileStatus fileStatus : fileStatuses) {
+            inserOrUpdateIndexingTimesStampStatement.write(fileStatus.filePathId.filePathId,
+                                                           fileStatus.lastModified);
+        }
+    }
+
+    SourceTimeStamps fetchIndexingTimeStamps() const
+    {
+        try {
+            Sqlite::DeferredTransaction transaction{database};
+
+            auto timeStamps = fetchIndexingTimeStampsStatement.template values<SourceTimeStamp, 2>(
+                1024);
+
+            transaction.commit();
+
+            return timeStamps;
+        } catch (const Sqlite::StatementIsBusy &) {
+            return fetchIndexingTimeStamps();
+        }
+    }
+
+    SourceTimeStamps fetchIncludedIndexingTimeStamps(FilePathId sourcePathId) const
+    {
+        try {
+            Sqlite::DeferredTransaction transaction{database};
+
+            auto timeStamps = fetchIncludedIndexingTimeStampsStatement
+                                  .template values<SourceTimeStamp, 2>(1024, sourcePathId.filePathId);
+
+            transaction.commit();
+
+            return timeStamps;
+        } catch (const Sqlite::StatementIsBusy &) {
+            return fetchIncludedIndexingTimeStamps(sourcePathId);
+        }
+    }
+
+    FilePathIds fetchDependentSourceIds(const FilePathIds &sourcePathIds) const override
+    {
+        try {
+            FilePathIds dependentSourceIds;
+
+            Sqlite::DeferredTransaction transaction{database};
+
+            for (FilePathId sourcePathId : sourcePathIds) {
+                FilePathIds newDependentSourceIds;
+                newDependentSourceIds.reserve(dependentSourceIds.size() + 1024);
+
+                auto newIds = fetchDependentSourceIdsStatement
+                                  .template values<FilePathId>(1024, sourcePathId.filePathId);
+
+                std::set_union(dependentSourceIds.begin(),
+                               dependentSourceIds.end(),
+                               newIds.begin(),
+                               newIds.end(),
+                               std::back_inserter(newDependentSourceIds));
+
+                dependentSourceIds = std::move(newDependentSourceIds);
+            }
+
+            transaction.commit();
+
+            return dependentSourceIds;
+        } catch (const Sqlite::StatementIsBusy &) {
+            return fetchDependentSourceIds(sourcePathIds);
+        }
+    }
+
     void fillTemporarySymbolsTable(const SymbolEntries &symbolEntries)
     {
         WriteStatement &statement = insertSymbolsToNewSymbolsStatement;
@@ -191,6 +278,25 @@ public:
         database};
     WriteStatement deleteNewSymbolsTableStatement{"DELETE FROM newSymbols", database};
     WriteStatement deleteNewLocationsTableStatement{"DELETE FROM newLocations", database};
+    WriteStatement inserOrUpdateIndexingTimesStampStatement{
+        "INSERT INTO fileStatuses(sourceId, indexingTimeStamp) VALUES (?001, ?002) ON "
+        "CONFLICT(sourceId) DO UPDATE SET indexingTimeStamp = ?002",
+        database};
+    mutable ReadStatement fetchIncludedIndexingTimeStampsStatement{
+        "WITH RECURSIVE collectedDependencies(sourceId) AS (VALUES(?) UNION SELECT "
+        "dependencySourceId FROM sourceDependencies, collectedDependencies WHERE "
+        "sourceDependencies.sourceId == collectedDependencies.sourceId) SELECT DISTINCT sourceId, "
+        "indexingTimeStamp FROM collectedDependencies NATURAL JOIN fileStatuses ORDER BY sourceId",
+        database};
+    mutable ReadStatement fetchIndexingTimeStampsStatement{
+        "SELECT sourceId, indexingTimeStamp FROM fileStatuses", database};
+    mutable ReadStatement fetchDependentSourceIdsStatement{
+        "WITH RECURSIVE collectedDependencies(sourceId) AS (VALUES(?) UNION SELECT "
+        "sourceDependencies.sourceId FROM sourceDependencies, collectedDependencies WHERE "
+        "sourceDependencies.dependencySourceId == collectedDependencies.sourceId) SELECT sourceId "
+        "FROM collectedDependencies WHERE sourceId NOT IN (SELECT dependencySourceId FROM "
+        "sourceDependencies) ORDER BY sourceId",
+        database};
 };
 
 } // namespace ClangBackEnd
diff --git a/src/tools/clangrefactoringbackend/source/symbolstorageinterface.h b/src/tools/clangrefactoringbackend/source/symbolstorageinterface.h
index 1d04c4d168..d3c8035e8c 100644
--- a/src/tools/clangrefactoringbackend/source/symbolstorageinterface.h
+++ b/src/tools/clangrefactoringbackend/source/symbolstorageinterface.h
@@ -28,6 +28,9 @@
 #include "sourcelocationentry.h"
 #include "symbolentry.h"
 
+#include <filestatus.h>
+#include <sourceentry.h>
+
 #include <compilermacro.h>
 #include <sqlitetransaction.h>
 
@@ -45,6 +48,11 @@ public:
     virtual void addSymbolsAndSourceLocations(const SymbolEntries &symbolEntries,
                                               const SourceLocationEntries &sourceLocations)
         = 0;
+    virtual void insertOrUpdateIndexingTimeStamps(const FilePathIds &filePathIds, TimeStamp indexingTimeStamp) = 0;
+    virtual void insertOrUpdateIndexingTimeStamps(const FileStatuses &fileStatuses) = 0;
+    virtual SourceTimeStamps fetchIndexingTimeStamps() const = 0;
+    virtual SourceTimeStamps fetchIncludedIndexingTimeStamps(FilePathId sourcePathId) const = 0;
+    virtual FilePathIds fetchDependentSourceIds(const FilePathIds &sourcePathIds) const = 0;
 
 protected:
     ~SymbolStorageInterface() = default;
diff --git a/tests/unit/unittest/builddependenciesprovider-test.cpp b/tests/unit/unittest/builddependenciesprovider-test.cpp
index 772a435a58..c9794c8cc0 100644
--- a/tests/unit/unittest/builddependenciesprovider-test.cpp
+++ b/tests/unit/unittest/builddependenciesprovider-test.cpp
@@ -58,7 +58,7 @@ class BuildDependenciesProvider : public testing::Test
 protected:
     NiceMock<MockSqliteTransactionBackend> mockSqliteTransactionBackend;
     NiceMock<MockBuildDependenciesStorage> mockBuildDependenciesStorage;
-    NiceMock<MockModifiedTimeChecker> mockModifiedTimeChecker;
+    NiceMock<MockSourceEntriesModifiedTimeChecker> mockModifiedTimeChecker;
     NiceMock<MockBuildDependencyGenerator> mockBuildDependenciesGenerator;
     ClangBackEnd::BuildDependenciesProvider provider{mockBuildDependenciesStorage,
                                                      mockModifiedTimeChecker,
diff --git a/tests/unit/unittest/clangdocument-test.cpp b/tests/unit/unittest/clangdocument-test.cpp
index 26a4ab1bfd..4978f41fd7 100644
--- a/tests/unit/unittest/clangdocument-test.cpp
+++ b/tests/unit/unittest/clangdocument-test.cpp
@@ -201,7 +201,7 @@ TEST_F(DocumentSlowTest, NeedsReparseAfterChangeOfMainFile)
     ASSERT_TRUE(document.isDirty());
 }
 
-TEST_F(DocumentSlowTest, NoNeedForReparsingForIndependendFile)
+TEST_F(DocumentSlowTest, NoNeedForReparsingForIndependentFile)
 {
     document.parse();
 
@@ -210,7 +210,7 @@ TEST_F(DocumentSlowTest, NoNeedForReparsingForIndependendFile)
     ASSERT_FALSE(document.isDirty());
 }
 
-TEST_F(DocumentSlowTest, NeedsReparsingForDependendFile)
+TEST_F(DocumentSlowTest, NeedsReparsingForDependentFile)
 {
     document.parse();
 
diff --git a/tests/unit/unittest/clangupdateannotationsjob-test.cpp b/tests/unit/unittest/clangupdateannotationsjob-test.cpp
index 0bcd5a67c0..79623619c1 100644
--- a/tests/unit/unittest/clangupdateannotationsjob-test.cpp
+++ b/tests/unit/unittest/clangupdateannotationsjob-test.cpp
@@ -97,16 +97,16 @@ TEST_F(UpdateAnnotationsJobSlowTest, DontSendAnnotationsIfDocumentRevisionChange
     ASSERT_TRUE(waitUntilJobFinished(job));
 }
 
-TEST_F(UpdateAnnotationsJobSlowTest, UpdatesDependendFilePaths)
+TEST_F(UpdateAnnotationsJobSlowTest, UpdatesDependentFilePaths)
 {
-    const QSet<Utf8String> dependendOnFilesBefore = document.dependedFilePaths();
+    const QSet<Utf8String> dependentOnFilesBefore = document.dependedFilePaths();
     job.setContext(jobContext);
     job.prepareAsyncRun();
 
     job.runAsync();
     ASSERT_TRUE(waitUntilJobFinished(job));
 
-    ASSERT_THAT(dependendOnFilesBefore, Not(document.dependedFilePaths()));
+    ASSERT_THAT(dependentOnFilesBefore, Not(document.dependedFilePaths()));
 }
 
 TEST_F(UpdateAnnotationsJobSlowTest, UpdatesUnresolvedFilePaths)
diff --git a/tests/unit/unittest/gtest-creator-printing.cpp b/tests/unit/unittest/gtest-creator-printing.cpp
index 8644edea4d..84add6b4a1 100644
--- a/tests/unit/unittest/gtest-creator-printing.cpp
+++ b/tests/unit/unittest/gtest-creator-printing.cpp
@@ -1230,6 +1230,16 @@ std::ostream &operator<<(std::ostream &out, const SourceEntry &entry)
                << typeToString(entry.hasMissingIncludes) << ")";
 }
 
+std::ostream &operator<<(std::ostream &out, const SourceTimeStamp &sourceTimeStamp)
+{
+    return out << "(" << sourceTimeStamp.sourceId << ", " << sourceTimeStamp.timeStamp << ")";
+}
+
+std::ostream &operator<<(std::ostream &out, const TimeStamp &timeStamp)
+{
+    return out << timeStamp.value;
+}
+
 const char *typeToString(IncludeSearchPathType type)
 {
     switch (type) {
diff --git a/tests/unit/unittest/gtest-creator-printing.h b/tests/unit/unittest/gtest-creator-printing.h
index 9e2c5632f5..2d83535d14 100644
--- a/tests/unit/unittest/gtest-creator-printing.h
+++ b/tests/unit/unittest/gtest-creator-printing.h
@@ -165,7 +165,7 @@ class UpdateProjectPartsMessage;
 class DocumentsChangedMessage;
 class DocumentVisibilityChangedMessage;
 class FilePath;
-template <char WindowsSlash>
+template<char WindowsSlash>
 class AbstractFilePathView;
 using FilePathView = AbstractFilePathView<'/'>;
 using NativeFilePathView = AbstractFilePathView<'\\'>;
@@ -190,6 +190,8 @@ class PchTask;
 class PchTaskSet;
 class BuildDependency;
 class SourceEntry;
+class SourceTimeStamp;
+class TimeStamp;
 class FilePathCaching;
 struct SlotUsage;
 class IncludeSearchPath;
@@ -281,6 +283,8 @@ std::ostream &operator<<(std::ostream &out, const PchTask &task);
 std::ostream &operator<<(std::ostream &out, const PchTaskSet &taskSet);
 std::ostream &operator<<(std::ostream &out, const BuildDependency &dependency);
 std::ostream &operator<<(std::ostream &out, const SourceEntry &entry);
+std::ostream &operator<<(std::ostream &out, const SourceTimeStamp &sourceTimeStamp);
+std::ostream &operator<<(std::ostream &out, const TimeStamp &timeStamp);
 std::ostream &operator<<(std::ostream &out, const SlotUsage &slotUsage);
 std::ostream &operator<<(std::ostream &out, const IncludeSearchPathType &pathType);
 std::ostream &operator<<(std::ostream &out, const IncludeSearchPath &path);
diff --git a/tests/unit/unittest/mockmodifiedtimechecker.h b/tests/unit/unittest/mockmodifiedtimechecker.h
index 5f0559f682..bf101988b1 100644
--- a/tests/unit/unittest/mockmodifiedtimechecker.h
+++ b/tests/unit/unittest/mockmodifiedtimechecker.h
@@ -29,9 +29,17 @@
 
 #include <modifiedtimecheckerinterface.h>
 
-class MockModifiedTimeChecker : public ClangBackEnd::ModifiedTimeCheckerInterface
+class MockSourceEntriesModifiedTimeChecker
+    : public ClangBackEnd::ModifiedTimeCheckerInterface<ClangBackEnd::SourceEntries>
 {
 public:
     MOCK_CONST_METHOD1(isUpToDate,
                        bool (const ClangBackEnd::SourceEntries &sourceEntries));
 };
+
+class MockSourceTimeStampsModifiedTimeChecker
+    : public ClangBackEnd::ModifiedTimeCheckerInterface<ClangBackEnd::SourceTimeStamps>
+{
+public:
+    MOCK_CONST_METHOD1(isUpToDate, bool(const ClangBackEnd::SourceTimeStamps &sourceTimeStamps));
+};
diff --git a/tests/unit/unittest/mockprojectpartsstorage.h b/tests/unit/unittest/mockprojectpartsstorage.h
index 114a7fab0e..e8dcbc94b2 100644
--- a/tests/unit/unittest/mockprojectpartsstorage.h
+++ b/tests/unit/unittest/mockprojectpartsstorage.h
@@ -56,5 +56,7 @@ public:
     MOCK_CONST_METHOD1(fetchProjectPartArtefact,
                        Utils::optional<ClangBackEnd::ProjectPartArtefact>(
                            ClangBackEnd::ProjectPartId projectPartId));
+    MOCK_METHOD1(resetIndexingTimeStamps,
+                 void(const ClangBackEnd::ProjectPartContainers &projectsParts));
     MOCK_METHOD0(transactionBackend, Sqlite::TransactionInterface &());
 };
diff --git a/tests/unit/unittest/mocksqlitereadstatement.cpp b/tests/unit/unittest/mocksqlitereadstatement.cpp
index c12d40b9ea..2e9d74acf6 100644
--- a/tests/unit/unittest/mocksqlitereadstatement.cpp
+++ b/tests/unit/unittest/mocksqlitereadstatement.cpp
@@ -222,6 +222,19 @@ SourceEntries MockSqliteReadStatement::values<SourceEntry, 4>(std::size_t reserv
     return valuesReturnSourceEntries(reserveSize, filePathId, projectPartId);
 }
 
+template<>
+SourceTimeStamps MockSqliteReadStatement::values<SourceTimeStamp, 2>(std::size_t reserveSize)
+{
+    return valuesReturnSourceTimeStamps(reserveSize);
+}
+
+template<>
+SourceTimeStamps MockSqliteReadStatement::values<SourceTimeStamp, 2>(std::size_t reserveSize,
+                                                                     const int &sourcePathId)
+{
+    return valuesReturnSourceTimeStamps(reserveSize, sourcePathId);
+}
+
 template <>
 Utils::optional<Sources::SourceNameAndDirectoryId>
 MockSqliteReadStatement::value<Sources::SourceNameAndDirectoryId, 2>(const int &id)
diff --git a/tests/unit/unittest/mocksqlitereadstatement.h b/tests/unit/unittest/mocksqlitereadstatement.h
index e3ab740b6e..135a6d1851 100644
--- a/tests/unit/unittest/mocksqlitereadstatement.h
+++ b/tests/unit/unittest/mocksqlitereadstatement.h
@@ -50,6 +50,8 @@
 using ClangBackEnd::FilePathIds;
 using ClangBackEnd::SourceEntries;
 using ClangBackEnd::SourceEntry;
+using ClangBackEnd::SourceTimeStamp;
+using ClangBackEnd::SourceTimeStamps;
 using ClangRefactoring::SourceLocation;
 using ClangRefactoring::SourceLocations;
 using std::int64_t;
@@ -136,6 +138,9 @@ public:
     MOCK_METHOD1(valueReturnProjectPartId,
                  Utils::optional<ClangBackEnd::ProjectPartId>(Utils::SmallStringView));
 
+    MOCK_METHOD1(valuesReturnSourceTimeStamps, SourceTimeStamps(std::size_t));
+    MOCK_METHOD2(valuesReturnSourceTimeStamps, SourceTimeStamps(std::size_t, int sourcePathId));
+
     template <typename ResultType,
               int ResultTypeCount = 1,
               typename... QueryType>
@@ -283,6 +288,13 @@ SourceEntries MockSqliteReadStatement::values<SourceEntry, 4>(std::size_t reserv
                                                               const int &,
                                                               const int &);
 
+template<>
+SourceTimeStamps MockSqliteReadStatement::values<SourceTimeStamp, 2>(std::size_t reserveSize);
+
+template<>
+SourceTimeStamps MockSqliteReadStatement::values<SourceTimeStamp, 2>(std::size_t reserveSize,
+                                                                     const int &sourcePathId);
+
 template <>
 Utils::optional<Sources::SourceNameAndDirectoryId>
 MockSqliteReadStatement::value<Sources::SourceNameAndDirectoryId, 2>(const int&);
diff --git a/tests/unit/unittest/mocksymbolstorage.h b/tests/unit/unittest/mocksymbolstorage.h
index a174389735..7b77868e8a 100644
--- a/tests/unit/unittest/mocksymbolstorage.h
+++ b/tests/unit/unittest/mocksymbolstorage.h
@@ -37,4 +37,11 @@ public:
    MOCK_METHOD2(addSymbolsAndSourceLocations,
                 void(const ClangBackEnd::SymbolEntries &symbolEentries,
                      const ClangBackEnd::SourceLocationEntries &sourceLocations));
+   MOCK_METHOD2(insertOrUpdateIndexingTimeStamps,
+                void(const FilePathIds &filePathIds, ClangBackEnd::TimeStamp indexingTimeStamp));
+   MOCK_METHOD1(insertOrUpdateIndexingTimeStamps, void(const ClangBackEnd::FileStatuses &));
+   MOCK_CONST_METHOD0(fetchIndexingTimeStamps, ClangBackEnd::SourceTimeStamps());
+   MOCK_CONST_METHOD1(fetchIncludedIndexingTimeStamps,
+                      ClangBackEnd::SourceTimeStamps(ClangBackEnd::FilePathId sourcePathId));
+   MOCK_CONST_METHOD1(fetchDependentSourceIds, FilePathIds(const FilePathIds &sourcePathIds));
 };
diff --git a/tests/unit/unittest/modifiedtimechecker-test.cpp b/tests/unit/unittest/modifiedtimechecker-test.cpp
index 8e0c881b38..ff0c3c66d8 100644
--- a/tests/unit/unittest/modifiedtimechecker-test.cpp
+++ b/tests/unit/unittest/modifiedtimechecker-test.cpp
@@ -57,7 +57,7 @@ protected:
     ClangBackEnd::FilePathCaching filePathCache{database};
     decltype(getModifiedTimeCallback.AsStdFunction()) callback = getModifiedTimeCallback
                                                                      .AsStdFunction();
-    ClangBackEnd::ModifiedTimeChecker checker{callback, filePathCache};
+    ClangBackEnd::ModifiedTimeChecker<> checker{callback, filePathCache};
     SourceEntries upToDateEntries = {{id("/path1"), SourceType::UserInclude, 100},
                                      {id("/path2"), SourceType::SystemInclude, 30}};
     SourceEntries notUpToDateEntries = {{id("/path1"), SourceType::UserInclude, 50},
diff --git a/tests/unit/unittest/projectpartsmanager-test.cpp b/tests/unit/unittest/projectpartsmanager-test.cpp
index 235a7553ba..b12cbb6b2e 100644
--- a/tests/unit/unittest/projectpartsmanager-test.cpp
+++ b/tests/unit/unittest/projectpartsmanager-test.cpp
@@ -302,6 +302,7 @@ TEST_F(ProjectPartsManager, UpdateCallsIfNewProjectPartIsAdded)
     EXPECT_CALL(mockProjectPartsStorage, updateProjectParts(ElementsAre(projectPartContainer1)));
     EXPECT_CALL(mockPrecompiledHeaderStorage,
                 deleteProjectPrecompiledHeaders(ElementsAre(projectPartContainer1.projectPartId)));
+    EXPECT_CALL(mockProjectPartsStorage, resetIndexingTimeStamps(ElementsAre(projectPartContainer1)));
 
     manager.update({projectPartContainer1});
 }
@@ -337,6 +338,16 @@ TEST_F(ProjectPartsManager, UpdateCallsNotDeleteProjectPrecompiledHeadersIfNoNew
     manager.update({projectPartContainer1});
 }
 
+TEST_F(ProjectPartsManager, UpdateCallsNotResetIndexingTimeStampsIfNoNewerProjectPartsExists)
+{
+    manager.update({projectPartContainer1});
+
+    EXPECT_CALL(mockProjectPartsStorage, resetIndexingTimeStamps(ElementsAre(projectPartContainer1)))
+        .Times(0);
+
+    manager.update({projectPartContainer1});
+}
+
 TEST_F(ProjectPartsManager, UpdateCallsIfOldProjectPartIsAdded)
 {
     EXPECT_CALL(mockProjectPartsStorage,
@@ -346,6 +357,8 @@ TEST_F(ProjectPartsManager, UpdateCallsIfOldProjectPartIsAdded)
     EXPECT_CALL(mockPrecompiledHeaderStorage,
                 deleteProjectPrecompiledHeaders(ElementsAre(projectPartContainer1.projectPartId)))
         .Times(0);
+    EXPECT_CALL(mockProjectPartsStorage, resetIndexingTimeStamps(ElementsAre(projectPartContainer1)))
+        .Times(0);
 
     manager.update({projectPartContainer1});
 }
@@ -361,6 +374,8 @@ TEST_F(ProjectPartsManager, UpdateCallsIfUpdatedProjectPartIsAdded)
                 updateProjectParts(ElementsAre(updatedProjectPartContainer1)));
     EXPECT_CALL(mockPrecompiledHeaderStorage,
                 deleteProjectPrecompiledHeaders(ElementsAre(projectPartContainer1.projectPartId)));
+    EXPECT_CALL(mockProjectPartsStorage,
+                resetIndexingTimeStamps(ElementsAre(updatedProjectPartContainer1)));
 
     manager.update({updatedProjectPartContainer1});
 }
diff --git a/tests/unit/unittest/projectpartsstorage-test.cpp b/tests/unit/unittest/projectpartsstorage-test.cpp
index 963248cd29..3c13f33ad6 100644
--- a/tests/unit/unittest/projectpartsstorage-test.cpp
+++ b/tests/unit/unittest/projectpartsstorage-test.cpp
@@ -27,12 +27,13 @@
 
 #include "mocksqlitedatabase.h"
 
+#include <builddependenciesstorage.h>
 #include <projectpartsstorage.h>
 #include <refactoringdatabaseinitializer.h>
 #include <sqlitedatabase.h>
 #include <sqlitereadstatement.h>
 #include <sqlitewritestatement.h>
-
+#include <symbolstorage.h>
 namespace {
 
 using ClangBackEnd::FilePathId;
@@ -104,6 +105,7 @@ protected:
     MockSqliteReadStatement &fetchProjectPartsHeadersByIdStatement = storage.fetchProjectPartsHeadersByIdStatement;
     MockSqliteReadStatement &fetchProjectPartsSourcesByIdStatement = storage.fetchProjectPartsSourcesByIdStatement;
     MockSqliteReadStatement &fetchProjectPrecompiledHeaderPathStatement = storage.fetchProjectPrecompiledHeaderPathStatement;
+    MockSqliteWriteStatement &resetDependentIndexingTimeStampsStatement = storage.resetDependentIndexingTimeStampsStatement;
     IncludeSearchPaths systemIncludeSearchPaths{{"/includes", 1, IncludeSearchPathType::BuiltIn},
                                                 {"/other/includes", 2, IncludeSearchPathType::System}};
     IncludeSearchPaths projectIncludeSearchPaths{{"/project/includes", 1, IncludeSearchPathType::User},
@@ -424,6 +426,35 @@ TEST_F(ProjectPartsStorage, FetchProjectPartArtefactByProjectPartIdReturnArtefac
     ASSERT_THAT(result, Eq(artefact));
 }
 
+TEST_F(ProjectPartsStorage, ResetDependentIndexingTimeStamps)
+{
+    InSequence s;
+
+    EXPECT_CALL(mockDatabase, immediateBegin());
+    EXPECT_CALL(resetDependentIndexingTimeStampsStatement, write(TypedEq<int>(3)));
+    EXPECT_CALL(resetDependentIndexingTimeStampsStatement, write(TypedEq<int>(4)));
+    EXPECT_CALL(resetDependentIndexingTimeStampsStatement, write(TypedEq<int>(7)));
+    EXPECT_CALL(resetDependentIndexingTimeStampsStatement, write(TypedEq<int>(8)));
+    EXPECT_CALL(mockDatabase, commit());
+
+    storage.resetIndexingTimeStamps({projectPart1, projectPart2});
+}
+
+TEST_F(ProjectPartsStorage, ResetDependentIndexingTimeStampsIsBusy)
+{
+    InSequence s;
+
+    EXPECT_CALL(mockDatabase, immediateBegin()).WillOnce(Throw(Sqlite::StatementIsBusy{""}));
+    EXPECT_CALL(mockDatabase, immediateBegin());
+    EXPECT_CALL(resetDependentIndexingTimeStampsStatement, write(TypedEq<int>(3)));
+    EXPECT_CALL(resetDependentIndexingTimeStampsStatement, write(TypedEq<int>(4)));
+    EXPECT_CALL(resetDependentIndexingTimeStampsStatement, write(TypedEq<int>(7)));
+    EXPECT_CALL(resetDependentIndexingTimeStampsStatement, write(TypedEq<int>(8)));
+    EXPECT_CALL(mockDatabase, commit());
+
+    storage.resetIndexingTimeStamps({projectPart1, projectPart2});
+}
+
 class ProjectPartsStorageSlow : public testing::Test, public Data
 {
     using Storage = ClangBackEnd::ProjectPartsStorage<Sqlite::Database>;
@@ -432,6 +463,8 @@ protected:
     Sqlite::Database database{":memory:", Sqlite::JournalMode::Memory};
     ClangBackEnd::RefactoringDatabaseInitializer<Sqlite::Database> databaseInitializer{database};
     Storage storage{database};
+    ClangBackEnd::SymbolStorage<> symbolStorage{database};
+    ClangBackEnd::BuildDependenciesStorage<> buildDependenciesStorage{database};
 };
 
 TEST_F(ProjectPartsStorageSlow, FetchProjectPartName)
@@ -469,4 +502,26 @@ TEST_F(ProjectPartsStorageSlow, FetchProjectParts)
 
     ASSERT_THAT(projectParts, ElementsAre(projectPart1, projectPart2));
 }
+
+TEST_F(ProjectPartsStorageSlow, ResetDependentIndexingTimeStamps)
+{
+    symbolStorage.insertOrUpdateIndexingTimeStamps({1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 34);
+    buildDependenciesStorage.insertOrUpdateSourceDependencies(
+        {{3, 1}, {4, 1}, {1, 2}, {7, 5}, {8, 6}, {6, 5}, {9, 10}});
+
+    storage.resetIndexingTimeStamps({projectPart1, projectPart2});
+
+    ASSERT_THAT(symbolStorage.fetchIndexingTimeStamps(),
+                ElementsAre(SourceTimeStamp{1, 0},
+                            SourceTimeStamp{2, 0},
+                            SourceTimeStamp{3, 0},
+                            SourceTimeStamp{4, 0},
+                            SourceTimeStamp{5, 0},
+                            SourceTimeStamp{6, 0},
+                            SourceTimeStamp{7, 0},
+                            SourceTimeStamp{8, 0},
+                            SourceTimeStamp{9, 34},
+                            SourceTimeStamp{10, 34}));
+}
+
 } // namespace
diff --git a/tests/unit/unittest/refactoringdatabaseinitializer-test.cpp b/tests/unit/unittest/refactoringdatabaseinitializer-test.cpp
index 4865e2ebff..7177060311 100644
--- a/tests/unit/unittest/refactoringdatabaseinitializer-test.cpp
+++ b/tests/unit/unittest/refactoringdatabaseinitializer-test.cpp
@@ -131,7 +131,7 @@ TEST_F(RefactoringDatabaseInitializer, AddFileStatusesTable)
         mockDatabase,
         execute(Eq(
             "CREATE TABLE IF NOT EXISTS fileStatuses(sourceId INTEGER PRIMARY KEY, size INTEGER, "
-            "lastModified INTEGER)")));
+            "lastModified INTEGER, indexingTimeStamp INTEGER)")));
 
     initializer.createFileStatusesTable();
 }
@@ -140,8 +140,19 @@ TEST_F(RefactoringDatabaseInitializer, AddSourceDependenciesTable)
 {
     InSequence s;
 
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE TABLE IF NOT EXISTS sourceDependencies(sourceId INTEGER, dependencySourceId INTEGER)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE INDEX IF NOT EXISTS index_sourceDependencies_sourceId_dependencySourceId ON sourceDependencies(sourceId, dependencySourceId)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE TABLE IF NOT EXISTS sourceDependencies(sourceId INTEGER, "
+                           "dependencySourceId INTEGER)")));
+    EXPECT_CALL(
+        mockDatabase,
+        execute(
+            Eq("CREATE INDEX IF NOT EXISTS index_sourceDependencies_sourceId_dependencySourceId ON "
+               "sourceDependencies(sourceId, dependencySourceId)")));
+    EXPECT_CALL(
+        mockDatabase,
+        execute(
+            Eq("CREATE INDEX IF NOT EXISTS index_sourceDependencies_dependencySourceId_sourceId ON "
+               "sourceDependencies(dependencySourceId, sourceId)")));
 
     initializer.createSourceDependenciesTable();
 }
@@ -189,40 +200,88 @@ TEST_F(RefactoringDatabaseInitializer, CreateInTheContructor)
 
     EXPECT_CALL(mockDatabase, isInitialized()).WillOnce(Return(false));
     EXPECT_CALL(mockDatabase, exclusiveBegin());
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE TABLE IF NOT EXISTS symbols(symbolId INTEGER PRIMARY KEY, usr TEXT, symbolName TEXT, symbolKind INTEGER, signature TEXT)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE INDEX IF NOT EXISTS index_symbols_usr ON symbols(usr)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE INDEX IF NOT EXISTS index_symbols_symbolKind_symbolName ON symbols(symbolKind, symbolName)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE TABLE IF NOT EXISTS locations(symbolId INTEGER, line INTEGER, column INTEGER, sourceId INTEGER, locationKind INTEGER)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE UNIQUE INDEX IF NOT EXISTS index_locations_sourceId_line_column ON locations(sourceId, line, column)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE INDEX IF NOT EXISTS index_locations_sourceId_locationKind ON locations(sourceId, locationKind)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE TABLE IF NOT EXISTS sources(sourceId INTEGER PRIMARY KEY, directoryId INTEGER, sourceName TEXT)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE UNIQUE INDEX IF NOT EXISTS index_sources_directoryId_sourceName ON sources(directoryId, sourceName)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE TABLE IF NOT EXISTS directories(directoryId INTEGER PRIMARY KEY, directoryPath TEXT)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE UNIQUE INDEX IF NOT EXISTS index_directories_directoryPath ON directories(directoryPath)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE TABLE IF NOT EXISTS symbols(symbolId INTEGER PRIMARY KEY, usr "
+                           "TEXT, symbolName TEXT, symbolKind INTEGER, signature TEXT)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE INDEX IF NOT EXISTS index_symbols_usr ON symbols(usr)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE INDEX IF NOT EXISTS index_symbols_symbolKind_symbolName ON "
+                           "symbols(symbolKind, symbolName)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE TABLE IF NOT EXISTS locations(symbolId INTEGER, line INTEGER, "
+                           "column INTEGER, sourceId INTEGER, locationKind INTEGER)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE UNIQUE INDEX IF NOT EXISTS index_locations_sourceId_line_column "
+                           "ON locations(sourceId, line, column)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE INDEX IF NOT EXISTS index_locations_sourceId_locationKind ON "
+                           "locations(sourceId, locationKind)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE TABLE IF NOT EXISTS sources(sourceId INTEGER PRIMARY KEY, "
+                           "directoryId INTEGER, sourceName TEXT)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE UNIQUE INDEX IF NOT EXISTS index_sources_directoryId_sourceName "
+                           "ON sources(directoryId, sourceName)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE TABLE IF NOT EXISTS directories(directoryId INTEGER PRIMARY "
+                           "KEY, directoryPath TEXT)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE UNIQUE INDEX IF NOT EXISTS index_directories_directoryPath ON "
+                           "directories(directoryPath)")));
     EXPECT_CALL(mockDatabase,
                 execute(
                     Eq("CREATE TABLE IF NOT EXISTS projectParts(projectPartId INTEGER PRIMARY "
                        "KEY, projectPartName TEXT, toolChainArguments TEXT, compilerMacros "
                        "TEXT, systemIncludeSearchPaths TEXT, projectIncludeSearchPaths TEXT, "
                        "language INTEGER, languageVersion INTEGER, languageExtension INTEGER)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE UNIQUE INDEX IF NOT EXISTS index_projectParts_projectPartName ON projectParts(projectPartName)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE UNIQUE INDEX IF NOT EXISTS index_projectParts_projectPartName "
+                           "ON projectParts(projectPartName)")));
     EXPECT_CALL(mockDatabase,
                 execute(Eq("CREATE TABLE IF NOT EXISTS projectPartsFiles(projectPartId INTEGER, "
                            "sourceId INTEGER, sourceType INTEGER, pchCreationTimeStamp INTEGER, "
                            "hasMissingIncludes INTEGER)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE UNIQUE INDEX IF NOT EXISTS index_projectPartsFiles_sourceId_projectPartId ON projectPartsFiles(sourceId, projectPartId)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE INDEX IF NOT EXISTS index_projectPartsFiles_projectPartId ON projectPartsFiles(projectPartId)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE TABLE IF NOT EXISTS usedMacros(usedMacroId INTEGER PRIMARY KEY, sourceId INTEGER, macroName TEXT)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE INDEX IF NOT EXISTS index_usedMacros_sourceId_macroName ON usedMacros(sourceId, macroName)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE INDEX IF NOT EXISTS index_usedMacros_macroName ON usedMacros(macroName)")));
+    EXPECT_CALL(
+        mockDatabase,
+        execute(
+            Eq("CREATE UNIQUE INDEX IF NOT EXISTS index_projectPartsFiles_sourceId_projectPartId "
+               "ON projectPartsFiles(sourceId, projectPartId)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE INDEX IF NOT EXISTS index_projectPartsFiles_projectPartId ON "
+                           "projectPartsFiles(projectPartId)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE TABLE IF NOT EXISTS usedMacros(usedMacroId INTEGER PRIMARY KEY, "
+                           "sourceId INTEGER, macroName TEXT)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE INDEX IF NOT EXISTS index_usedMacros_sourceId_macroName ON "
+                           "usedMacros(sourceId, macroName)")));
+    EXPECT_CALL(
+        mockDatabase,
+        execute(
+            Eq("CREATE INDEX IF NOT EXISTS index_usedMacros_macroName ON usedMacros(macroName)")));
     EXPECT_CALL(
         mockDatabase,
         execute(Eq(
             "CREATE TABLE IF NOT EXISTS fileStatuses(sourceId INTEGER PRIMARY KEY, size INTEGER, "
-            "lastModified INTEGER)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE TABLE IF NOT EXISTS sourceDependencies(sourceId INTEGER, dependencySourceId INTEGER)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE INDEX IF NOT EXISTS index_sourceDependencies_sourceId_dependencySourceId ON sourceDependencies(sourceId, dependencySourceId)")));
-    EXPECT_CALL(mockDatabase, execute(Eq("CREATE TABLE IF NOT EXISTS precompiledHeaders(projectPartId INTEGER PRIMARY KEY, projectPchPath TEXT, projectPchBuildTime INTEGER, systemPchPath TEXT, systemPchBuildTime INTEGER)")));
+            "lastModified INTEGER, indexingTimeStamp INTEGER)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE TABLE IF NOT EXISTS sourceDependencies(sourceId INTEGER, "
+                           "dependencySourceId INTEGER)")));
+    EXPECT_CALL(
+        mockDatabase,
+        execute(
+            Eq("CREATE INDEX IF NOT EXISTS index_sourceDependencies_sourceId_dependencySourceId ON "
+               "sourceDependencies(sourceId, dependencySourceId)")));
+    EXPECT_CALL(
+        mockDatabase,
+        execute(
+            Eq("CREATE INDEX IF NOT EXISTS index_sourceDependencies_dependencySourceId_sourceId ON "
+               "sourceDependencies(dependencySourceId, sourceId)")));
+    EXPECT_CALL(mockDatabase,
+                execute(Eq("CREATE TABLE IF NOT EXISTS precompiledHeaders(projectPartId INTEGER "
+                           "PRIMARY KEY, projectPchPath TEXT, projectPchBuildTime INTEGER, "
+                           "systemPchPath TEXT, systemPchBuildTime INTEGER)")));
     EXPECT_CALL(mockDatabase,
                 execute(Eq("CREATE TABLE IF NOT EXISTS projectPartsHeaders(projectPartId INTEGER, "
                            "sourceId INTEGER)")));
@@ -271,7 +330,7 @@ TEST_F(RefactoringDatabaseInitializer, DontCreateIfAlreadyInitialized)
     EXPECT_CALL(mockDatabase, execute(Eq("CREATE INDEX IF NOT EXISTS index_usedMacros_macroName ON usedMacros(macroName)"))).Times(0);
     EXPECT_CALL(mockDatabase,
                 execute(Eq("CREATE TABLE IF NOT EXISTS fileStatuses(sourceId INTEGER PRIMARY KEY, "
-                           "size INTEGER, lastModified INTEGER, isInPrecompiledHeader INTEGER)")))
+                           "size INTEGER, lastModified INTEGER, indexingTimeStamp INTEGER)")))
         .Times(0);
     EXPECT_CALL(mockDatabase, execute(Eq("CREATE TABLE IF NOT EXISTS sourceDependencies(sourceId INTEGER, dependencySourceId INTEGER)"))).Times(0);
     EXPECT_CALL(mockDatabase, execute(Eq("CREATE INDEX IF NOT EXISTS index_sourceDependencies_sourceId_dependencySourceId ON sourceDependencies(sourceId, dependencySourceId)"))).Times(0);
diff --git a/tests/unit/unittest/symbolindexer-test.cpp b/tests/unit/unittest/symbolindexer-test.cpp
index edfcb286ad..0be2d3b0e5 100644
--- a/tests/unit/unittest/symbolindexer-test.cpp
+++ b/tests/unit/unittest/symbolindexer-test.cpp
@@ -28,6 +28,7 @@
 #include "mockbuilddependenciesstorage.h"
 #include "mockclangpathwatcher.h"
 #include "mockfilepathcaching.h"
+#include "mockmodifiedtimechecker.h"
 #include "mockprecompiledheaderstorage.h"
 #include "mockprojectpartsstorage.h"
 #include "mocksqlitetransactionbackend.h"
@@ -113,7 +114,12 @@ protected:
             .WillByDefault(Return(artefact));
         ON_CALL(mockBuildDependenciesStorage, fetchLowestLastModifiedTime(A<FilePathId>())).WillByDefault(Return(-1));
         ON_CALL(mockCollector, collectSymbols()).WillByDefault(Return(true));
-
+        ON_CALL(mockSymbolStorage, fetchDependentSourceIds(sourceFileIds))
+            .WillByDefault(Return(sourceFileIds));
+        ON_CALL(mockSymbolStorage, fetchDependentSourceIds(ElementsAre(sourceFileIds[0])))
+            .WillByDefault(Return(FilePathIds{sourceFileIds[0]}));
+        ON_CALL(mockSymbolStorage, fetchDependentSourceIds(ElementsAre(main1PathId)))
+            .WillByDefault(Return(FilePathIds{main1PathId}));
         mockCollector.setIsUsed(false);
 
         generatedFiles.update(unsaved);
@@ -230,6 +236,10 @@ protected:
                                                     Utils::Language::Cxx,
                                                     Utils::LanguageVersion::CXX14,
                                                     Utils::LanguageExtension::None};
+    ClangBackEnd::SourceTimeStamps dependentSourceTimeStamps1{{1, 32}};
+    ClangBackEnd::SourceTimeStamps dependentSourceTimeStamps2{{2, 35}};
+    ClangBackEnd::FileStatuses fileStatuses1{{1, 0, 32}};
+    ClangBackEnd::FileStatuses fileStatuses2{{2, 0, 35}};
     Utils::optional<ClangBackEnd::ProjectPartArtefact > nullArtefact;
     ClangBackEnd::ProjectPartPch projectPartPch{74, "/path/to/pch", 4};
     NiceMock<MockSqliteTransactionBackend> mockSqliteTransactionBackend;
@@ -243,6 +253,7 @@ protected:
     Manager collectorManger{generatedFiles};
     NiceMock<MockFunction<void(int, int)>> mockSetProgressCallback;
     ClangBackEnd::ProgressCounter progressCounter{mockSetProgressCallback.AsStdFunction()};
+    NiceMock<MockSourceTimeStampsModifiedTimeChecker> mockModifiedTimeChecker;
     ClangBackEnd::SymbolIndexer indexer{indexerQueue,
                                         mockSymbolStorage,
                                         mockBuildDependenciesStorage,
@@ -251,7 +262,8 @@ protected:
                                         filePathCache,
                                         fileStatusCache,
                                         mockSqliteTransactionBackend,
-                                        mockProjectPartsStorage};
+                                        mockProjectPartsStorage,
+                                        mockModifiedTimeChecker};
     SymbolIndexerTaskQueue indexerQueue{indexerScheduler, progressCounter};
     Scheduler indexerScheduler{collectorManger,
                                indexerQueue,
@@ -493,6 +505,58 @@ TEST_F(SymbolIndexer, UpdateProjectPartsCallsInOrderButGetsAnErrorForCollectingS
     indexer.updateProjectParts({projectPart1});
 }
 
+TEST_F(SymbolIndexer, UpdateProjectPartsFetchIncludedIndexingTimeStamps)
+{
+    InSequence s;
+    ProjectPartContainer projectPart{1,
+                                     {"-Wno-pragma-once-outside-header"},
+                                     {{"BAR", "1", 1}, {"FOO", "1", 2}},
+                                     Utils::clone(systemIncludeSearchPaths),
+                                     Utils::clone(projectIncludeSearchPaths),
+                                     {header1PathId},
+                                     {main1PathId, main2PathId},
+                                     Utils::Language::Cxx,
+                                     Utils::LanguageVersion::CXX14,
+                                     Utils::LanguageExtension::None};
+
+    EXPECT_CALL(mockSymbolStorage, fetchIncludedIndexingTimeStamps(Eq(main1PathId)))
+        .WillOnce(Return(dependentSourceTimeStamps1));
+    EXPECT_CALL(mockModifiedTimeChecker, isUpToDate(dependentSourceTimeStamps1));
+    EXPECT_CALL(mockSymbolStorage, fetchIncludedIndexingTimeStamps(Eq(main2PathId)))
+        .WillOnce(Return(dependentSourceTimeStamps2));
+    EXPECT_CALL(mockModifiedTimeChecker, isUpToDate(dependentSourceTimeStamps2));
+    EXPECT_CALL(mockCollector, fileStatuses()).WillRepeatedly(ReturnRef(fileStatuses1));
+    EXPECT_CALL(mockSymbolStorage, insertOrUpdateIndexingTimeStamps(fileStatuses1));
+    EXPECT_CALL(mockCollector, fileStatuses()).WillRepeatedly(ReturnRef(fileStatuses2));
+    EXPECT_CALL(mockSymbolStorage, insertOrUpdateIndexingTimeStamps(fileStatuses2));
+
+    indexer.updateProjectParts({projectPart});
+}
+
+TEST_F(SymbolIndexer, DependentSourceAreNotUpToDate)
+{
+    InSequence s;
+
+    EXPECT_CALL(mockModifiedTimeChecker, isUpToDate(_)).WillOnce(Return(false));
+    EXPECT_CALL(mockCollector, setFile(main1PathId, _));
+    EXPECT_CALL(mockCollector, collectSymbols()).WillOnce(Return(true));
+    EXPECT_CALL(mockSymbolStorage, addSymbolsAndSourceLocations(symbolEntries, sourceLocations));
+
+    indexer.updateProjectParts({projectPart1});
+}
+
+TEST_F(SymbolIndexer, DependentSourceAreUpToDate)
+{
+    InSequence s;
+
+    EXPECT_CALL(mockModifiedTimeChecker, isUpToDate(_)).WillOnce(Return(true));
+    EXPECT_CALL(mockCollector, setFile(main1PathId, _)).Times(0);
+    EXPECT_CALL(mockCollector, collectSymbols()).Times(0);
+    EXPECT_CALL(mockSymbolStorage, addSymbolsAndSourceLocations(symbolEntries, sourceLocations)).Times(0);
+
+    indexer.updateProjectParts({projectPart1});
+}
+
 TEST_F(SymbolIndexer, CallSetNotifier)
 {
     EXPECT_CALL(mockPathWatcher, setNotifier(_));
@@ -505,7 +569,8 @@ TEST_F(SymbolIndexer, CallSetNotifier)
                                         filePathCache,
                                         fileStatusCache,
                                         mockSqliteTransactionBackend,
-                                        mockProjectPartsStorage};
+                                        mockProjectPartsStorage,
+                                        mockModifiedTimeChecker};
 }
 
 TEST_F(SymbolIndexer, PathChangedCallsFetchProjectPartArtefactInStorage)
@@ -516,6 +581,54 @@ TEST_F(SymbolIndexer, PathChangedCallsFetchProjectPartArtefactInStorage)
     indexer.pathsChanged(sourceFileIds);
 }
 
+TEST_F(SymbolIndexer, PathChangedCallsFetchSourcePathIds)
+{
+    InSequence s;
+
+    EXPECT_CALL(mockSymbolStorage, fetchDependentSourceIds(sourceFileIds))
+        .WillOnce(Return(FilePathIds{2, 6, 5}));
+    EXPECT_CALL(mockProjectPartsStorage, fetchProjectPartArtefact(FilePathId{2}));
+    EXPECT_CALL(mockProjectPartsStorage, fetchProjectPartArtefact(FilePathId{6}));
+    EXPECT_CALL(mockProjectPartsStorage, fetchProjectPartArtefact(FilePathId{5}));
+
+    indexer.pathsChanged(sourceFileIds);
+}
+
+TEST_F(SymbolIndexer, PathChangedFetchIncludedIndexingTimeStamps)
+{
+    InSequence s;
+    ProjectPartContainer projectPart{1,
+                                     {"-Wno-pragma-once-outside-header"},
+                                     {{"BAR", "1", 1}, {"FOO", "1", 2}},
+                                     Utils::clone(systemIncludeSearchPaths),
+                                     Utils::clone(projectIncludeSearchPaths),
+                                     {header1PathId},
+                                     {main1PathId, main2PathId},
+                                     Utils::Language::Cxx,
+                                     Utils::LanguageVersion::CXX14,
+                                     Utils::LanguageExtension::None};
+
+    EXPECT_CALL(mockSymbolStorage, fetchDependentSourceIds(_)).WillOnce(Return(FilePathIds{1, 2}));
+    EXPECT_CALL(mockSymbolStorage, fetchIncludedIndexingTimeStamps(Eq(1)))
+        .WillOnce(Return(dependentSourceTimeStamps1));
+    EXPECT_CALL(mockSymbolStorage, fetchIncludedIndexingTimeStamps(Eq(2)))
+        .WillOnce(Return(dependentSourceTimeStamps2));
+    EXPECT_CALL(mockCollector, fileStatuses()).WillOnce(ReturnRef(fileStatuses1));
+    EXPECT_CALL(mockSymbolStorage, insertOrUpdateIndexingTimeStamps(fileStatuses1));
+    EXPECT_CALL(mockCollector, fileStatuses()).WillOnce(ReturnRef(fileStatuses2));
+    EXPECT_CALL(mockSymbolStorage, insertOrUpdateIndexingTimeStamps(fileStatuses2));
+
+    indexer.pathsChanged({1, 3});
+}
+
+TEST_F(SymbolIndexer, PathChangedFetchesDependentSourceIdsFromStorage)
+{
+    EXPECT_CALL(mockProjectPartsStorage, fetchProjectPartArtefact(sourceFileIds[0]));
+    EXPECT_CALL(mockProjectPartsStorage, fetchProjectPartArtefact(sourceFileIds[1]));
+
+    indexer.pathsChanged(sourceFileIds);
+}
+
 TEST_F(SymbolIndexer, UpdateChangedPathCallsInOrder)
 {
     InSequence s;
@@ -797,6 +910,7 @@ TEST_F(SymbolIndexer, PathsChangedUpdatesFileStatusCache)
     auto sourceId = filePathId(TESTDATA_DIR "/symbolindexer_pathChanged.cpp");
     auto oldLastModified = fileStatusCache.lastModifiedTime(sourceId);
     touchFile(sourceId);
+    ON_CALL(mockSymbolStorage, fetchDependentSourceIds(_)).WillByDefault(Return(FilePathIds{sourceId}));
 
     indexer.pathsChanged({sourceId});
 
diff --git a/tests/unit/unittest/symbolstorage-test.cpp b/tests/unit/unittest/symbolstorage-test.cpp
index 059b1a3c0f..a29b7f92aa 100644
--- a/tests/unit/unittest/symbolstorage-test.cpp
+++ b/tests/unit/unittest/symbolstorage-test.cpp
@@ -28,17 +28,22 @@
 #include "mockfilepathcaching.h"
 #include "mocksqlitedatabase.h"
 
-#include <symbolstorage.h>
+#include <builddependenciesstorage.h>
+#include <refactoringdatabaseinitializer.h>
 #include <sqlitedatabase.h>
+#include <sqlitereadstatement.h>
+#include <sqlitewritestatement.h>
+#include <symbolstorage.h>
 
 #include <utils/optional.h>
 
 namespace {
-
 using ClangBackEnd::FilePathCachingInterface;
+using ClangBackEnd::FilePathId;
 using ClangBackEnd::SourceLocationEntries;
 using ClangBackEnd::SourceLocationEntry;
 using ClangBackEnd::SourceLocationKind;
+using ClangBackEnd::SourceTimeStamp;
 using ClangBackEnd::SymbolEntries;
 using ClangBackEnd::SymbolEntry;
 using ClangBackEnd::SymbolIndex;
@@ -64,6 +69,10 @@ protected:
     MockSqliteWriteStatement &insertNewLocationsInLocationsStatement = storage.insertNewLocationsInLocationsStatement;
     MockSqliteWriteStatement &deleteNewSymbolsTableStatement = storage.deleteNewSymbolsTableStatement;
     MockSqliteWriteStatement &deleteNewLocationsTableStatement = storage.deleteNewLocationsTableStatement;
+    MockSqliteWriteStatement &inserOrUpdateIndexingTimesStampStatement = storage.inserOrUpdateIndexingTimesStampStatement;
+    MockSqliteReadStatement &fetchIndexingTimeStampsStatement = storage.fetchIndexingTimeStampsStatement;
+    MockSqliteReadStatement &fetchIncludedIndexingTimeStampsStatement = storage.fetchIncludedIndexingTimeStampsStatement;
+    MockSqliteReadStatement &fetchDependentSourceIdsStatement = storage.fetchDependentSourceIdsStatement;
     SymbolEntries symbolEntries{{1, {"functionUSR", "function", SymbolKind::Function}},
                                 {2, {"function2USR", "function2", SymbolKind::Function}}};
     SourceLocationEntries sourceLocations{{1, 3, {42, 23}, SourceLocationKind::Declaration},
@@ -183,5 +192,145 @@ TEST_F(SymbolStorage, AddTablesInConstructor)
     Storage storage{mockDatabase};
 }
 
+TEST_F(SymbolStorage, FetchIndexingTimeStampsIsBusy)
+{
+    InSequence s;
+
+    EXPECT_CALL(mockDatabase, deferredBegin());
+    EXPECT_CALL(fetchIndexingTimeStampsStatement, valuesReturnSourceTimeStamps(1024))
+        .WillOnce(Throw(Sqlite::StatementIsBusy{""}));
+    EXPECT_CALL(mockDatabase, rollback());
+    EXPECT_CALL(mockDatabase, deferredBegin());
+    EXPECT_CALL(fetchIndexingTimeStampsStatement, valuesReturnSourceTimeStamps(1024));
+    EXPECT_CALL(mockDatabase, commit());
+
+    storage.fetchIndexingTimeStamps();
+}
+
+TEST_F(SymbolStorage, InsertIndexingTimeStamp)
+{
+    ClangBackEnd::FileStatuses fileStatuses{{1, 0, 34}, {2, 0, 37}};
+
+    EXPECT_CALL(inserOrUpdateIndexingTimesStampStatement, write(TypedEq<int>(1), TypedEq<int>(34)));
+    EXPECT_CALL(inserOrUpdateIndexingTimesStampStatement, write(TypedEq<int>(2), TypedEq<int>(37)));
+
+    storage.insertOrUpdateIndexingTimeStamps(fileStatuses);
+}
+
+TEST_F(SymbolStorage, InsertIndexingTimeStampsIsBusy)
+{
+    InSequence s;
+
+    EXPECT_CALL(mockDatabase, immediateBegin()).WillOnce(Throw(Sqlite::StatementIsBusy{""}));
+    EXPECT_CALL(mockDatabase, immediateBegin());
+    EXPECT_CALL(inserOrUpdateIndexingTimesStampStatement, write(TypedEq<int>(1), TypedEq<int>(34)));
+    EXPECT_CALL(inserOrUpdateIndexingTimesStampStatement, write(TypedEq<int>(2), TypedEq<int>(34)));
+    EXPECT_CALL(mockDatabase, commit());
+
+    storage.insertOrUpdateIndexingTimeStamps({1, 2}, 34);
+}
+
+TEST_F(SymbolStorage, FetchIncludedIndexingTimeStampsIsBusy)
+{
+    InSequence s;
+
+    EXPECT_CALL(mockDatabase, deferredBegin());
+    EXPECT_CALL(fetchIncludedIndexingTimeStampsStatement,
+                valuesReturnSourceTimeStamps(1024, TypedEq<int>(1)))
+        .WillOnce(Throw(Sqlite::StatementIsBusy{""}));
+    EXPECT_CALL(mockDatabase, rollback());
+    EXPECT_CALL(mockDatabase, deferredBegin());
+    EXPECT_CALL(fetchIncludedIndexingTimeStampsStatement,
+                valuesReturnSourceTimeStamps(1024, TypedEq<int>(1)));
+    EXPECT_CALL(mockDatabase, commit());
+
+    storage.fetchIncludedIndexingTimeStamps(1);
+}
+
+TEST_F(SymbolStorage, FetchDependentSourceIdsIsBusy)
+{
+    InSequence s;
+
+    EXPECT_CALL(mockDatabase, deferredBegin());
+    EXPECT_CALL(fetchDependentSourceIdsStatement, valuesReturnFilePathIds(1024, TypedEq<int>(3)));
+    EXPECT_CALL(fetchDependentSourceIdsStatement, valuesReturnFilePathIds(1024, TypedEq<int>(2)))
+        .WillOnce(Throw(Sqlite::StatementIsBusy{""}));
+    EXPECT_CALL(mockDatabase, rollback());
+    EXPECT_CALL(mockDatabase, deferredBegin());
+    EXPECT_CALL(fetchDependentSourceIdsStatement, valuesReturnFilePathIds(1024, TypedEq<int>(3)));
+    EXPECT_CALL(fetchDependentSourceIdsStatement, valuesReturnFilePathIds(1024, TypedEq<int>(2)));
+    EXPECT_CALL(fetchDependentSourceIdsStatement, valuesReturnFilePathIds(1024, TypedEq<int>(7)));
+    EXPECT_CALL(mockDatabase, commit());
+
+    storage.fetchDependentSourceIds({3, 2, 7});
+}
+
+class SymbolStorageSlow : public testing::Test
+{
+protected:
+    Sqlite::Database database{":memory:", Sqlite::JournalMode::Memory};
+    ClangBackEnd::RefactoringDatabaseInitializer<Sqlite::Database> databaseInitializer{database};
+    ClangBackEnd::SymbolStorage<> storage{database};
+    ClangBackEnd::BuildDependenciesStorage<> buildDependenciesStorage{database};
+};
+
+TEST_F(SymbolStorageSlow, InsertIndexingTimeStamps)
+{
+    storage.insertOrUpdateIndexingTimeStamps({1, 2}, 34);
+
+    ASSERT_THAT(storage.fetchIndexingTimeStamps(),
+                ElementsAre(SourceTimeStamp{1, 34}, SourceTimeStamp{2, 34}));
+}
+
+TEST_F(SymbolStorageSlow, UpdateIndexingTimeStamps)
+{
+    storage.insertOrUpdateIndexingTimeStamps({1, 2}, 34);
+
+    storage.insertOrUpdateIndexingTimeStamps({1}, 37);
+
+    ASSERT_THAT(storage.fetchIndexingTimeStamps(),
+                ElementsAre(SourceTimeStamp{1, 37}, SourceTimeStamp{2, 34}));
 }
 
+TEST_F(SymbolStorageSlow, InsertIndexingTimeStamp)
+{
+    storage.insertOrUpdateIndexingTimeStamps({{1, 0, 34}, {2, 0, 37}});
+
+    ASSERT_THAT(storage.fetchIndexingTimeStamps(),
+                ElementsAre(SourceTimeStamp{1, 34}, SourceTimeStamp{2, 37}));
+}
+
+TEST_F(SymbolStorageSlow, UpdateIndexingTimeStamp)
+{
+    storage.insertOrUpdateIndexingTimeStamps({{1, 0, 34}, {2, 0, 34}});
+
+    storage.insertOrUpdateIndexingTimeStamps({{2, 0, 37}});
+
+    ASSERT_THAT(storage.fetchIndexingTimeStamps(),
+                ElementsAre(SourceTimeStamp{1, 34}, SourceTimeStamp{2, 37}));
+}
+
+TEST_F(SymbolStorageSlow, FetchIncludedIndexingTimeStamps)
+{
+    storage.insertOrUpdateIndexingTimeStamps({1, 2, 3, 4, 5}, 34);
+    buildDependenciesStorage.insertOrUpdateSourceDependencies({{1, 2}, {1, 3}, {2, 3}, {3, 4}, {5, 3}});
+
+    auto timeStamps = storage.fetchIncludedIndexingTimeStamps(1);
+
+    ASSERT_THAT(timeStamps,
+                ElementsAre(SourceTimeStamp{1, 34},
+                            SourceTimeStamp{2, 34},
+                            SourceTimeStamp{3, 34},
+                            SourceTimeStamp{4, 34}));
+}
+
+TEST_F(SymbolStorageSlow, FetchDependentSourceIds)
+{
+    buildDependenciesStorage.insertOrUpdateSourceDependencies(
+        {{1, 2}, {1, 3}, {2, 3}, {4, 2}, {5, 6}, {7, 6}});
+
+    auto sourceIds = storage.fetchDependentSourceIds({3, 2, 7});
+
+    ASSERT_THAT(sourceIds, ElementsAre(FilePathId{1}, FilePathId{4}, FilePathId{7}));
+}
+} // namespace
diff --git a/tests/unit/unittest/translationunitupdater-test.cpp b/tests/unit/unittest/translationunitupdater-test.cpp
index b491018956..eecc06b8a7 100644
--- a/tests/unit/unittest/translationunitupdater-test.cpp
+++ b/tests/unit/unittest/translationunitupdater-test.cpp
@@ -113,7 +113,7 @@ TEST_F(TranslationUnitUpdaterSlowTest, NotUpdatingParseTimePointForReparseOnly)
     ASSERT_FALSE(result.hasParsed());
 }
 
-TEST_F(TranslationUnitUpdaterSlowTest, UpdatesDependendOnFilesOnParse)
+TEST_F(TranslationUnitUpdaterSlowTest, UpdatesDependentOnFilesOnParse)
 {
     ::TranslationUnitUpdater updater = createUpdater(createInput());