diff --git a/src/libs/clangsupport/filecontainerv2.h b/src/libs/clangsupport/filecontainerv2.h
index aa7248fb5e2..e6e8c6622f4 100644
--- a/src/libs/clangsupport/filecontainerv2.h
+++ b/src/libs/clangsupport/filecontainerv2.h
@@ -27,6 +27,7 @@
 
 #include "clangsupport_global.h"
 #include "filepath.h"
+#include "filepathid.h"
 
 #include <vector>
 
@@ -39,13 +40,15 @@ public:
     FileContainer() = default;
 
     FileContainer(FilePath &&filePath,
+                  FilePathId filePathId,
                   Utils::SmallString &&unsavedFileContent,
                   Utils::SmallStringVector &&commandLineArguments = {},
                   quint32 documentRevision = 0)
-        : filePath(std::move(filePath)),
-          unsavedFileContent(std::move(unsavedFileContent)),
-          commandLineArguments(std::move(commandLineArguments)),
-          documentRevision(documentRevision)
+        : filePath(std::move(filePath))
+        , filePathId(filePathId)
+        , unsavedFileContent(std::move(unsavedFileContent))
+        , commandLineArguments(std::move(commandLineArguments))
+        , documentRevision(documentRevision)
     {
     }
 
@@ -81,16 +84,11 @@ public:
              < std::tie(second.filePath, second.documentRevision, second.unsavedFileContent, second.commandLineArguments);
     }
 
-    FileContainer clone() const
-    {
-        return FileContainer(filePath.clone(),
-                             unsavedFileContent.clone(),
-                             commandLineArguments.clone(),
-                             documentRevision);
-    }
+    FileContainer clone() const { return *this; }
 
 public:
     FilePath filePath;
+    FilePathId filePathId;
     Utils::SmallString unsavedFileContent;
     Utils::SmallStringVector commandLineArguments;
     quint32 documentRevision = 0;
diff --git a/src/libs/clangsupport/filepathcache.h b/src/libs/clangsupport/filepathcache.h
index ecc84570285..541769b0b51 100644
--- a/src/libs/clangsupport/filepathcache.h
+++ b/src/libs/clangsupport/filepathcache.h
@@ -67,13 +67,20 @@ public:
     FilePathCache(FilePathStorage &filePathStorage)
         : m_filePathStorage(filePathStorage)
     {
-        m_directoryPathCache.populate(filePathStorage.fetchAllDirectories());
-        m_fileNameCache.populate(filePathStorage.fetchAllSources());
+        populateIfEmpty();
     }
 
     FilePathCache(FilePathCache &&) = default;
     FilePathCache &operator=(FilePathCache &&) = default;
 
+    void populateIfEmpty()
+    {
+        if (m_fileNameCache.isEmpty()) {
+            m_directoryPathCache.populate(m_filePathStorage.fetchAllDirectories());
+            m_fileNameCache.populate(m_filePathStorage.fetchAllSources());
+        }
+    }
+
     template<typename Cache>
     Cache clone()
     {
@@ -126,8 +133,7 @@ public:
             return FileNameEntry{entry.sourceName, entry.directoryId};
         };
 
-        FileNameEntry entry = m_fileNameCache.string(filePathId.filePathId,
-                                                     fetchSoureNameAndDirectoryId);
+        auto entry = m_fileNameCache.string(filePathId.filePathId, fetchSoureNameAndDirectoryId);
 
         auto fetchDirectoryPath = [&] (int id) { return m_filePathStorage.fetchDirectoryPath(id); };
 
@@ -157,9 +163,6 @@ public:
             return FileNameEntry{entry.sourceName, entry.directoryId};
         };
 
-        FileNameEntry entry = m_fileNameCache.string(filePathId.filePathId,
-                                                     fetchSoureNameAndDirectoryId);
-
         return m_fileNameCache.string(filePathId.filePathId, fetchSoureNameAndDirectoryId).directoryId;
     }
 
diff --git a/src/libs/clangsupport/filepathcaching.cpp b/src/libs/clangsupport/filepathcaching.cpp
index e2b23e7ad66..f6d9ba9691d 100644
--- a/src/libs/clangsupport/filepathcaching.cpp
+++ b/src/libs/clangsupport/filepathcaching.cpp
@@ -57,6 +57,11 @@ void FilePathCaching::addFilePaths(const FilePaths &filePaths)
     m_cache.addFilePaths(filePaths);
 }
 
+void FilePathCaching::populateIfEmpty()
+{
+    m_cache.populateIfEmpty();
+}
+
 FilePathId CopyableFilePathCaching::filePathId(FilePathView filePath) const
 {
     return m_cache.filePathId(filePath);
@@ -87,4 +92,9 @@ void CopyableFilePathCaching::addFilePaths(const FilePaths &filePaths)
     m_cache.addFilePaths(filePaths);
 }
 
+void CopyableFilePathCaching::populateIfEmpty()
+{
+    m_cache.populateIfEmpty();
+}
+
 } // namespace ClangBackEnd
diff --git a/src/libs/clangsupport/filepathcaching.h b/src/libs/clangsupport/filepathcaching.h
index 17f1fb1d0e3..7c1f3434019 100644
--- a/src/libs/clangsupport/filepathcaching.h
+++ b/src/libs/clangsupport/filepathcaching.h
@@ -56,6 +56,7 @@ public:
     Utils::PathString directoryPath(DirectoryPathId directoryPathId) const override;
     DirectoryPathId directoryPathId(FilePathId filePathId) const override;
     void addFilePaths(const ClangBackEnd::FilePaths &filePaths) override;
+    void populateIfEmpty() override;
 
 private:
     Factory m_factory;
@@ -80,6 +81,7 @@ public:
     Utils::PathString directoryPath(DirectoryPathId directoryPathId) const override;
     DirectoryPathId directoryPathId(FilePathId filePathId) const override;
     void addFilePaths(const ClangBackEnd::FilePaths &filePaths) override;
+    void populateIfEmpty() override;
 
 private:
     Cache m_cache;
diff --git a/src/libs/clangsupport/filepathcachinginterface.h b/src/libs/clangsupport/filepathcachinginterface.h
index 67e30d1c5ce..69be405d37d 100644
--- a/src/libs/clangsupport/filepathcachinginterface.h
+++ b/src/libs/clangsupport/filepathcachinginterface.h
@@ -45,6 +45,7 @@ public:
     virtual DirectoryPathId directoryPathId(FilePathId filePathId) const = 0;
     virtual Utils::PathString directoryPath(DirectoryPathId directoryPathId) const = 0;
     virtual void addFilePaths(const ClangBackEnd::FilePaths &filePaths) = 0;
+    virtual void populateIfEmpty() = 0;
 
     template<typename Container>
     FilePathIds filePathIds(Container &&filePaths) const
diff --git a/src/libs/clangsupport/generatedfiles.cpp b/src/libs/clangsupport/generatedfiles.cpp
index 644137886ba..22b1e8044a9 100644
--- a/src/libs/clangsupport/generatedfiles.cpp
+++ b/src/libs/clangsupport/generatedfiles.cpp
@@ -53,7 +53,7 @@ void GeneratedFiles::update(const V2::FileContainers &fileContainers)
     V2::FileContainers unionFileContainers;
     unionFileContainers.reserve(m_fileContainers.size() + fileContainers.size());
 
-    auto compare = [] (const V2::FileContainer &first, const V2::FileContainer &second) {
+    auto compare = [](const V2::FileContainer &first, const V2::FileContainer &second) {
         return first.filePath < second.filePath;
     };
 
@@ -69,10 +69,7 @@ void GeneratedFiles::update(const V2::FileContainers &fileContainers)
 
 class Compare {
 public:
-    bool operator()(const FilePath &first, const FilePath &second)
-    {
-        return first < second;
-    }
+    bool operator()(const FilePath &first, const FilePath &second) { return first < second; }
     bool operator()(const V2::FileContainer &first, const V2::FileContainer &second)
     {
         return first.filePath < second.filePath;
@@ -116,4 +113,16 @@ const V2::FileContainers &GeneratedFiles::fileContainers() const
     return m_fileContainers;
 }
 
+FilePathIds GeneratedFiles::filePathIds() const
+{
+    auto ids = Utils::transform<FilePathIds>(m_fileContainers,
+                                             [](const V2::FileContainer &fileContainer) {
+                                                 return fileContainer.filePathId;
+                                             });
+
+    std::sort(ids.begin(), ids.end());
+
+    return ids;
+}
+
 } // namespace ClangBackEnd
diff --git a/src/libs/clangsupport/generatedfiles.h b/src/libs/clangsupport/generatedfiles.h
index 933b0d111bf..3e87048be9c 100644
--- a/src/libs/clangsupport/generatedfiles.h
+++ b/src/libs/clangsupport/generatedfiles.h
@@ -38,6 +38,7 @@ public:
     bool isValid() const;
 
     const V2::FileContainers &fileContainers() const;
+    FilePathIds filePathIds() const;
 
 private:
     V2::FileContainers m_fileContainers;
diff --git a/src/libs/clangsupport/generatedfilesinterface.h b/src/libs/clangsupport/generatedfilesinterface.h
index 85a50ffa387..72a1dfccfb4 100644
--- a/src/libs/clangsupport/generatedfilesinterface.h
+++ b/src/libs/clangsupport/generatedfilesinterface.h
@@ -38,6 +38,7 @@ public:
     virtual bool isValid() const = 0;
 
     virtual const V2::FileContainers &fileContainers() const = 0;
+    virtual FilePathIds filePathIds() const = 0;
 
 protected:
     ~GeneratedFilesInterface() = default;
diff --git a/src/libs/clangsupport/projectpartsstorage.h b/src/libs/clangsupport/projectpartsstorage.h
index 4ff1789c93b..492a46f648c 100644
--- a/src/libs/clangsupport/projectpartsstorage.h
+++ b/src/libs/clangsupport/projectpartsstorage.h
@@ -109,26 +109,33 @@ public:
         }
     }
 
+    ProjectPartId fetchProjectPartIdUnguarded(Utils::SmallStringView projectPartName) const override
+    {
+        auto optionalProjectPartId = fetchProjectPartIdStatement.template value<ProjectPartId>(
+            projectPartName);
+
+        if (optionalProjectPartId) {
+            return *optionalProjectPartId;
+        } else {
+            insertProjectPartNameStatement.write(projectPartName);
+
+            return static_cast<int>(database.lastInsertedRowId());
+        }
+
+        return {};
+    }
+
     ProjectPartId fetchProjectPartId(Utils::SmallStringView projectPartName) const override
     {
         try {
             Sqlite::DeferredTransaction transaction{database};
 
-            ProjectPartId projectPartId;
-            auto optionalProjectPartId = fetchProjectPartIdStatement.template value<ProjectPartId>(
-                projectPartName);
-
-            if (optionalProjectPartId) {
-                projectPartId = *optionalProjectPartId;
-            } else {
-                insertProjectPartNameStatement.write(projectPartName);
-
-                projectPartId = static_cast<int>(database.lastInsertedRowId());
-            }
+            ProjectPartId projectPartId = fetchProjectPartIdUnguarded(projectPartName);
 
             transaction.commit();
 
             return projectPartId;
+
         } catch (const Sqlite::StatementIsBusy &) {
             return fetchProjectPartId(projectPartName);
         }
@@ -330,6 +337,23 @@ public:
                                        Utils::SmallString::number(projectPartId.projectPathId));
     }
 
+    Internal::ProjectPartNameIds fetchAllProjectPartNamesAndIds() const
+    {
+        try {
+            Sqlite::DeferredTransaction transaction{database};
+
+            ReadStatement &statement = fetchAllProjectPartNamesAndIdsStatement;
+
+            auto values = statement.template values<Internal::ProjectPartNameId, 2>(256);
+
+            transaction.commit();
+
+            return values;
+        } catch (const Sqlite::StatementIsBusy &) {
+            return fetchAllProjectPartNamesAndIds();
+        }
+    }
+
 public:
     Sqlite::ImmediateNonThrowingDestructorTransaction transaction;
     Database &database;
@@ -383,5 +407,7 @@ public:
         "SELECT projectPchBuildTime FROM precompiledHeaders WHERE projectPartId = ?", database};
     WriteStatement resetDependentIndexingTimeStampsStatement{
         "UPDATE fileStatuses SET indexingTimeStamp = NULL WHERE sourceId = ?", database};
+    mutable ReadStatement fetchAllProjectPartNamesAndIdsStatement{
+        "SELECT projectPartName, projectPartId FROM projectParts", database};
 };
 } // namespace ClangBackEnd
diff --git a/src/libs/clangsupport/projectpartsstorageinterface.h b/src/libs/clangsupport/projectpartsstorageinterface.h
index 2d0675e6579..ec1ce65dd06 100644
--- a/src/libs/clangsupport/projectpartsstorageinterface.h
+++ b/src/libs/clangsupport/projectpartsstorageinterface.h
@@ -25,7 +25,8 @@
 
 #pragma once
 
-#include <projectpartcontainer.h>
+#include "projectpartcontainer.h"
+#include "projectpartstoragestructs.h"
 
 #include <sqlitetransaction.h>
 #include <utils/optional.h>
@@ -46,8 +47,10 @@ public:
 
     virtual ProjectPartContainers fetchProjectParts() const = 0;
     virtual ProjectPartContainers fetchProjectParts(const ProjectPartIds &projectPartIds) const = 0;
+    virtual ProjectPartId fetchProjectPartIdUnguarded(Utils::SmallStringView projectPartName) const = 0;
     virtual ProjectPartId fetchProjectPartId(Utils::SmallStringView projectPartName) const = 0;
     virtual Utils::PathString fetchProjectPartName(ProjectPartId projectPartId) const = 0;
+    virtual Internal::ProjectPartNameIds fetchAllProjectPartNamesAndIds() const = 0;
     virtual void updateProjectPart(ProjectPartId projectPartId,
                                    const Utils::SmallStringVector &commandLineArguments,
                                    const CompilerMacros &compilerMacros,
diff --git a/src/plugins/clangpchmanager/projectupdater.cpp b/src/plugins/clangpchmanager/projectupdater.cpp
index 5bb1cf5ccda..e006357e0c5 100644
--- a/src/plugins/clangpchmanager/projectupdater.cpp
+++ b/src/plugins/clangpchmanager/projectupdater.cpp
@@ -46,8 +46,11 @@
 #include <utils/algorithm.h>
 #include <utils/namevalueitem.h>
 
+#include <QDirIterator>
+
 #include <algorithm>
 #include <functional>
+#include <iostream>
 
 namespace ClangPchManager {
 
@@ -68,6 +71,7 @@ void ProjectUpdater::updateProjectParts(const std::vector<CppTools::ProjectPart
                                         Utils::SmallStringVector &&toolChainArguments)
 {
     addProjectFilesToFilePathCache(projectParts);
+    fetchProjectPartIds(projectParts);
 
     m_server.updateProjectParts(
         ClangBackEnd::UpdateProjectPartsMessage{toProjectPartContainers(projectParts),
@@ -237,7 +241,7 @@ void updateWithSettings(ClangBackEnd::CompilerMacros &macros,
 } // namespace
 
 ClangBackEnd::CompilerMacros ProjectUpdater::createCompilerMacros(
-    const ProjectExplorer::Macros &projectMacros, Utils::NameValueItems &&settingsMacros) const
+    const ProjectExplorer::Macros &projectMacros, Utils::NameValueItems &&settingsMacros)
 {
     int index = 0;
     auto macros = Utils::transform<ClangBackEnd::CompilerMacros>(
@@ -347,10 +351,10 @@ ClangBackEnd::ProjectPartContainer ProjectUpdater::toProjectPartContainer(
 
     auto includeSearchPaths = createIncludeSearchPaths(*projectPart);
 
-    const QByteArray projectPartName = projectPart->id().toUtf8();
-
-    ClangBackEnd::ProjectPartId projectPartId = m_projectPartsStorage.fetchProjectPartId(
-        projectPartName);
+    ClangBackEnd::ProjectPartId projectPartId = m_projectPartIdCache.stringId(
+        Utils::PathString{projectPart->id()}, [&](Utils::SmallStringView projectPartName) {
+            return m_projectPartsStorage.fetchProjectPartId(projectPartName);
+        });
 
     ClangIndexingProjectSettings *settings = m_settingsManager.settings(projectPart->project);
 
@@ -415,36 +419,31 @@ ClangBackEnd::FilePaths ProjectUpdater::createExcludedPaths(
 
 QString ProjectUpdater::fetchProjectPartName(ClangBackEnd::ProjectPartId projectPartId) const
 {
-    return m_projectPartsStorage.fetchProjectPartName(projectPartId).toQString();
+    return QString(m_projectPartIdCache.string(projectPartId.projectPathId,
+                                               [&](ClangBackEnd::ProjectPartId projectPartId) {
+                                                   return m_projectPartsStorage.fetchProjectPartName(
+                                                       projectPartId);
+                                               }));
 }
 
 ClangBackEnd::ProjectPartIds ProjectUpdater::toProjectPartIds(
-    const QStringList &projectPartNames) const
+    const QStringList &projectPartNamesAsQString) const
 {
     ClangBackEnd::ProjectPartIds projectPartIds;
     projectPartIds.reserve(projectPartIds.size());
 
-    std::transform(projectPartNames.begin(),
-                   projectPartNames.end(),
-                   std::back_inserter(projectPartIds),
-                   [&](const QString &projectPartName) {
-                       return m_projectPartsStorage.fetchProjectPartId(
-                           Utils::SmallString{projectPartName});
-                   });
+    auto projectPartNames = Utils::transform<std::vector<Utils::PathString>>(
+        projectPartNamesAsQString, [&](const QString &projectPartName) { return projectPartName; });
 
-    return projectPartIds;
+    return m_projectPartIdCache.stringIds(projectPartNames, [&](Utils::SmallStringView projectPartName) {
+        return m_projectPartsStorage.fetchProjectPartId(projectPartName);
+    });
 }
 
 void ProjectUpdater::addProjectFilesToFilePathCache(const std::vector<CppTools::ProjectPart *> &projectParts)
 {
-    std::size_t fileCount = std::accumulate(projectParts.begin(),
-                                            projectParts.end(),
-                                            std::size_t(0),
-                                            [](std::size_t value, CppTools::ProjectPart *projectPart) {
-                                                return value + std::size_t(projectPart->files.size());
-                                            });
     ClangBackEnd::FilePaths filePaths;
-    filePaths.reserve(fileCount);
+    filePaths.reserve(10000);
 
     for (CppTools::ProjectPart *projectPart : projectParts) {
         for (const CppTools::ProjectFile &file : projectPart->files)
@@ -455,4 +454,28 @@ void ProjectUpdater::addProjectFilesToFilePathCache(const std::vector<CppTools::
     m_filePathCache.addFilePaths(filePaths);
 }
 
+void ProjectUpdater::fetchProjectPartIds(const std::vector<CppTools::ProjectPart *> &projectParts)
+{
+    std::unique_ptr<Sqlite::DeferredTransaction> transaction;
+
+    auto projectPartNames = Utils::transform<std::vector<Utils::PathString>>(
+        projectParts, [](CppTools::ProjectPart *projectPart) { return projectPart->id(); });
+
+    auto projectPartNameViews = Utils::transform<std::vector<Utils::SmallStringView>>(
+        projectPartNames,
+        [](const Utils::PathString &projectPartName) { return projectPartName.toStringView(); });
+
+    m_projectPartIdCache
+        .addStrings(std::move(projectPartNameViews), [&](Utils::SmallStringView projectPartName) {
+            if (!transaction)
+                transaction = std::make_unique<Sqlite::DeferredTransaction>(
+                    m_projectPartsStorage.transactionBackend());
+            return m_projectPartsStorage.fetchProjectPartIdUnguarded(projectPartName);
+        });
+
+    if (transaction)
+        transaction->commit();
+
+} // namespace ClangPchManager
+
 } // namespace ClangPchManager
diff --git a/src/plugins/clangpchmanager/projectupdater.h b/src/plugins/clangpchmanager/projectupdater.h
index c3f793dc2fd..16d662004fb 100644
--- a/src/plugins/clangpchmanager/projectupdater.h
+++ b/src/plugins/clangpchmanager/projectupdater.h
@@ -34,6 +34,8 @@
 #include <includesearchpath.h>
 #include <projectpartcontainer.h>
 #include <projectpartsstorageinterface.h>
+#include <projectpartstoragestructs.h>
+#include <stringcache.h>
 
 #include <projectexplorer/headerpath.h>
 
@@ -66,6 +68,14 @@ class ClangIndexingProjectSettings;
 
 class CLANGPCHMANAGER_EXPORT ProjectUpdater
 {
+    using StringCache = ClangBackEnd::StringCache<Utils::PathString,
+                                                  Utils::SmallStringView,
+                                                  ClangBackEnd::ProjectPartId,
+                                                  ClangBackEnd::NonLockingMutex,
+                                                  decltype(&Utils::reverseCompare),
+                                                  Utils::reverseCompare,
+                                                  ClangBackEnd::Internal::ProjectPartNameId>;
+
 public:
     struct SystemAndProjectIncludeSearchPaths
     {
@@ -77,11 +87,13 @@ public:
                    ClangBackEnd::FilePathCachingInterface &filePathCache,
                    ClangBackEnd::ProjectPartsStorageInterface &projectPartsStorage,
                    ClangIndexingSettingsManager &settingsManager)
-        : m_server(server)
-        , m_filePathCache(filePathCache)
+        : m_filePathCache(filePathCache)
+        , m_server(server)
         , m_projectPartsStorage(projectPartsStorage)
         , m_settingsManager(settingsManager)
-    {}
+    {
+        m_projectPartIdCache.populate(m_projectPartsStorage.fetchAllProjectPartNamesAndIds());
+    }
 
     void updateProjectParts(const std::vector<CppTools::ProjectPart *> &projectParts,
                             Utils::SmallStringVector &&toolChainArguments);
@@ -104,8 +116,8 @@ public:
     void addToHeaderAndSources(HeaderAndSources &headerAndSources,
                                const CppTools::ProjectFile &projectFile) const;
     static QStringList toolChainArguments(CppTools::ProjectPart *projectPart);
-    ClangBackEnd::CompilerMacros createCompilerMacros(const ProjectExplorer::Macros &projectMacros,
-                                                      Utils::NameValueItems &&settingsMacros) const;
+    static ClangBackEnd::CompilerMacros createCompilerMacros(const ProjectExplorer::Macros &projectMacros,
+                                                             Utils::NameValueItems &&settingsMacros);
     static SystemAndProjectIncludeSearchPaths createIncludeSearchPaths(
         const CppTools::ProjectPart &projectPart);
     static ClangBackEnd::FilePaths createExcludedPaths(
@@ -115,16 +127,19 @@ public:
 
     ClangBackEnd::ProjectPartIds toProjectPartIds(const QStringList &projectPartNames) const;
 
-private:
     void addProjectFilesToFilePathCache(const std::vector<CppTools::ProjectPart *> &projectParts);
+    void fetchProjectPartIds(const std::vector<CppTools::ProjectPart *> &projectParts);
+
+protected:
+    ClangBackEnd::FilePathCachingInterface &m_filePathCache;
 
 private:
     ClangBackEnd::GeneratedFiles m_generatedFiles;
     ClangBackEnd::FilePaths m_excludedPaths;
     ClangBackEnd::ProjectManagementServerInterface &m_server;
-    ClangBackEnd::FilePathCachingInterface &m_filePathCache;
     ClangBackEnd::ProjectPartsStorageInterface &m_projectPartsStorage;
     ClangIndexingSettingsManager &m_settingsManager;
+    mutable StringCache m_projectPartIdCache;
 };
 
 } // namespace ClangPchManager
diff --git a/src/plugins/clangpchmanager/qtcreatorprojectupdater.cpp b/src/plugins/clangpchmanager/qtcreatorprojectupdater.cpp
index 5331e2ef052..9a3b1498cc2 100644
--- a/src/plugins/clangpchmanager/qtcreatorprojectupdater.cpp
+++ b/src/plugins/clangpchmanager/qtcreatorprojectupdater.cpp
@@ -29,6 +29,8 @@
 
 #include <projectexplorer/project.h>
 
+#include <filepathcachinginterface.h>
+
 namespace ClangPchManager {
 
 namespace Internal {
@@ -38,16 +40,21 @@ CppTools::CppModelManager *cppModelManager()
     return CppTools::CppModelManager::instance();
 }
 
-std::vector<ClangBackEnd::V2::FileContainer> createGeneratedFiles()
+std::vector<ClangBackEnd::V2::FileContainer> createGeneratedFiles(
+    ClangBackEnd::FilePathCachingInterface &filePathCache)
 {
     auto abstractEditors = CppTools::CppModelManager::instance()->abstractEditorSupports();
     std::vector<ClangBackEnd::V2::FileContainer> generatedFiles;
     generatedFiles.reserve(std::size_t(abstractEditors.size()));
 
-    auto toFileContainer = [] (const CppTools::AbstractEditorSupport *abstractEditor) {
-        return  ClangBackEnd::V2::FileContainer(ClangBackEnd::FilePath(abstractEditor->fileName()),
-                                                Utils::SmallString::fromQByteArray(abstractEditor->contents()),
-                                                {});
+    auto toFileContainer = [&](const CppTools::AbstractEditorSupport *abstractEditor) {
+        ClangBackEnd::FilePath filePath(abstractEditor->fileName());
+        ClangBackEnd::FilePathId filePathId = filePathCache.filePathId(filePath);
+        return ClangBackEnd::V2::FileContainer(std::move(filePath),
+                                               filePathId,
+                                               Utils::SmallString::fromQByteArray(
+                                                   abstractEditor->contents()),
+                                               {});
     };
 
     std::transform(abstractEditors.begin(),
diff --git a/src/plugins/clangpchmanager/qtcreatorprojectupdater.h b/src/plugins/clangpchmanager/qtcreatorprojectupdater.h
index 143ffea655f..1cada833e7d 100644
--- a/src/plugins/clangpchmanager/qtcreatorprojectupdater.h
+++ b/src/plugins/clangpchmanager/qtcreatorprojectupdater.h
@@ -32,6 +32,8 @@
 
 #include <filecontainerv2.h>
 
+#include <utils/algorithm.h>
+
 #include <QObject>
 
 namespace ProjectExplorer {
@@ -46,7 +48,8 @@ namespace ClangPchManager {
 
 namespace Internal {
 CLANGPCHMANAGER_EXPORT CppTools::CppModelManager *cppModelManager();
-CLANGPCHMANAGER_EXPORT std::vector<ClangBackEnd::V2::FileContainer> createGeneratedFiles();
+CLANGPCHMANAGER_EXPORT std::vector<ClangBackEnd::V2::FileContainer> createGeneratedFiles(
+    ClangBackEnd::FilePathCachingInterface &filePathCache);
 CLANGPCHMANAGER_EXPORT std::vector<CppTools::ProjectPart*> createProjectParts(ProjectExplorer::Project *project);
 }
 
@@ -83,9 +86,13 @@ public:
         ProjectUpdaterType::removeProjectParts(projectPartIds);
     }
 
-    void abstractEditorUpdated(const QString &filePath, const QByteArray &contents)
+    void abstractEditorUpdated(const QString &qFilePath, const QByteArray &contents)
     {
-        ProjectUpdaterType::updateGeneratedFiles({{ClangBackEnd::FilePath{filePath}, contents}});
+        ClangBackEnd::FilePath filePath{qFilePath};
+        ClangBackEnd::FilePathId filePathId = ProjectUpdaterType::m_filePathCache.filePathId(
+            filePath);
+
+        ProjectUpdaterType::updateGeneratedFiles({{std::move(filePath), filePathId, contents}});
     }
 
     void abstractEditorRemoved(const QString &filePath)
@@ -98,6 +105,14 @@ protected:
                           const Utils::FilePath &,
                           const Utils::FilePathList &targets) override
     {
+        auto filePaths = Utils::transform<ClangBackEnd::FilePaths>(targets,
+                                                                   [](const Utils::FilePath &filePath) {
+                                                                       return ClangBackEnd::FilePath{
+                                                                           filePath.toString()};
+                                                                   });
+
+        ProjectUpdater::m_filePathCache.addFilePaths(filePaths);
+
         for (const Utils::FilePath &target : targets)
             abstractEditorUpdated(target.toString(), {});
     }
@@ -105,7 +120,8 @@ protected:
 private:
     void connectToCppModelManager()
     {
-        ProjectUpdaterType::updateGeneratedFiles(Internal::createGeneratedFiles());
+        ProjectUpdaterType::updateGeneratedFiles(
+            Internal::createGeneratedFiles(ProjectUpdaterType::m_filePathCache));
 
         QObject::connect(Internal::cppModelManager(),
                          &CppTools::CppModelManager::projectPartsUpdated,
diff --git a/src/plugins/clangrefactoring/clangqueryprojectsfindfilter.cpp b/src/plugins/clangrefactoring/clangqueryprojectsfindfilter.cpp
index 5e6246ad5e4..f60aaff6e8c 100644
--- a/src/plugins/clangrefactoring/clangqueryprojectsfindfilter.cpp
+++ b/src/plugins/clangrefactoring/clangqueryprojectsfindfilter.cpp
@@ -82,10 +82,9 @@ void ClangQueryProjectsFindFilter::requestSourceRangesAndDiagnostics(const QStri
 {
     const QString filePath = temporaryFile.fileName();
 
-    ClangBackEnd::RequestSourceRangesAndDiagnosticsForQueryMessage message(queryText,
-                                                                           {ClangBackEnd::FilePath(filePath),
-                                                                            exampleContent,
-                                                                            {"cc",  "-std=c++1z", toNative(filePath)}});
+    ClangBackEnd::RequestSourceRangesAndDiagnosticsForQueryMessage message(
+        queryText,
+        {ClangBackEnd::FilePath(filePath), 1, exampleContent, {"cc", "-std=c++1z", toNative(filePath)}});
 
     m_server.requestSourceRangesAndDiagnosticsForQueryMessage(std::move(message));
 }
@@ -204,10 +203,9 @@ void appendSource(std::vector<ClangBackEnd::V2::FileContainer> &sources,
 
     if (!unsavedContentContains(sourceFilePath, unsavedContent) && !isCHeader(projectFile.kind)) {
         sources.emplace_back(ClangBackEnd::FilePath(projectFile.path),
+                             -1,
                              "",
-                             createCommandLine(projectPart.data(),
-                                               projectFile.path,
-                                               projectFile.kind));
+                             createCommandLine(projectPart.data(), projectFile.path, projectFile.kind));
     }
 }
 
diff --git a/src/plugins/clangrefactoring/qtcreatorclangqueryfindfilter.cpp b/src/plugins/clangrefactoring/qtcreatorclangqueryfindfilter.cpp
index 05c378b196d..e3dc7ee4e87 100644
--- a/src/plugins/clangrefactoring/qtcreatorclangqueryfindfilter.cpp
+++ b/src/plugins/clangrefactoring/qtcreatorclangqueryfindfilter.cpp
@@ -108,10 +108,12 @@ std::vector<ClangBackEnd::V2::FileContainer> createUnsavedContents()
     std::vector<ClangBackEnd::V2::FileContainer> unsavedContents;
     unsavedContents.reserve(std::size_t(abstractEditors.size()));
 
-    auto toFileContainer = [] (const CppTools::AbstractEditorSupport *abstractEditor) {
-        return  ClangBackEnd::V2::FileContainer(ClangBackEnd::FilePath(abstractEditor->fileName()),
-                                                Utils::SmallString::fromQByteArray(abstractEditor->contents()),
-                                                {});
+    auto toFileContainer = [](const CppTools::AbstractEditorSupport *abstractEditor) {
+        return ClangBackEnd::V2::FileContainer(ClangBackEnd::FilePath(abstractEditor->fileName()),
+                                               -1,
+                                               Utils::SmallString::fromQByteArray(
+                                                   abstractEditor->contents()),
+                                               {});
     };
 
     std::transform(abstractEditors.begin(),
diff --git a/src/plugins/clangrefactoring/qtcreatorrefactoringprojectupdater.cpp b/src/plugins/clangrefactoring/qtcreatorrefactoringprojectupdater.cpp
index 2d71b7b9fb6..415186d5558 100644
--- a/src/plugins/clangrefactoring/qtcreatorrefactoringprojectupdater.cpp
+++ b/src/plugins/clangrefactoring/qtcreatorrefactoringprojectupdater.cpp
@@ -37,16 +37,21 @@ CppTools::CppModelManager *cppModelManager()
     return CppTools::CppModelManager::instance();
 }
 
-std::vector<ClangBackEnd::V2::FileContainer> createGeneratedFiles()
+std::vector<ClangBackEnd::V2::FileContainer> createGeneratedFiles(
+    ClangBackEnd::FilePathCachingInterface &filePathCache)
 {
     auto abstractEditors = CppTools::CppModelManager::instance()->abstractEditorSupports();
     std::vector<ClangBackEnd::V2::FileContainer> generatedFiles;
     generatedFiles.reserve(std::size_t(abstractEditors.size()));
 
-    auto toFileContainer = [] (const CppTools::AbstractEditorSupport *abstractEditor) {
-        return  ClangBackEnd::V2::FileContainer(ClangBackEnd::FilePath(abstractEditor->fileName()),
-                                                Utils::SmallString::fromQByteArray(abstractEditor->contents()),
-                                                {});
+    auto toFileContainer = [&](const CppTools::AbstractEditorSupport *abstractEditor) {
+        ClangBackEnd::FilePath filePath{abstractEditor->fileName()};
+        ClangBackEnd::FilePathId filePathId = filePathCache.filePathId(filePath);
+        return ClangBackEnd::V2::FileContainer(std::move(filePath),
+                                               filePathId,
+                                               Utils::SmallString::fromQByteArray(
+                                                   abstractEditor->contents()),
+                                               {});
     };
 
     std::transform(abstractEditors.begin(),
@@ -76,9 +81,12 @@ QtCreatorRefactoringProjectUpdater::QtCreatorRefactoringProjectUpdater(
     connectToCppModelManager();
 }
 
-void QtCreatorRefactoringProjectUpdater::abstractEditorUpdated(const QString &filePath, const QByteArray &contents)
+void QtCreatorRefactoringProjectUpdater::abstractEditorUpdated(const QString &qFilePath,
+                                                               const QByteArray &contents)
 {
-    RefactoringProjectUpdater::updateGeneratedFiles({{ClangBackEnd::FilePath{filePath}, contents}});
+    ClangBackEnd::FilePath filePath{qFilePath};
+    ClangBackEnd::FilePathId filePathId = m_filePathCache.filePathId(filePath);
+    RefactoringProjectUpdater::updateGeneratedFiles({{std::move(filePath), filePathId, contents}});
 }
 
 void QtCreatorRefactoringProjectUpdater::abstractEditorRemoved(const QString &filePath)
@@ -88,7 +96,7 @@ void QtCreatorRefactoringProjectUpdater::abstractEditorRemoved(const QString &fi
 
 void QtCreatorRefactoringProjectUpdater::connectToCppModelManager()
 {
-    RefactoringProjectUpdater::updateGeneratedFiles(createGeneratedFiles());
+    RefactoringProjectUpdater::updateGeneratedFiles(createGeneratedFiles(m_filePathCache));
 
     QObject::connect(cppModelManager(),
                      &CppTools::CppModelManager::abstractEditorSupportContentsUpdated,
diff --git a/src/tools/clangpchmanagerbackend/clangpchmanagerbackendmain.cpp b/src/tools/clangpchmanagerbackend/clangpchmanagerbackendmain.cpp
index 1dd3f9acbe0..7a871bb0337 100644
--- a/src/tools/clangpchmanagerbackend/clangpchmanagerbackendmain.cpp
+++ b/src/tools/clangpchmanagerbackend/clangpchmanagerbackendmain.cpp
@@ -232,9 +232,8 @@ struct Data // because we have a cycle dependency
                                            pchTaskGenerator,
                                            projectParts,
                                            generatedFiles,
-                                           buildDependencyStorage/*,
-                                           buildDependencyProvider,
-                                           filePathCache*/};
+                                           buildDependencyStorage,
+                                           filePathCache};
     TaskScheduler systemTaskScheduler{pchCreatorManager,
                                       pchTaskQueue,
                                       pchCreationProgressCounter,
diff --git a/src/tools/clangpchmanagerbackend/source/pchmanagerserver.cpp b/src/tools/clangpchmanagerbackend/source/pchmanagerserver.cpp
index ee3d3d02aab..fa69cd56ca7 100644
--- a/src/tools/clangpchmanagerbackend/source/pchmanagerserver.cpp
+++ b/src/tools/clangpchmanagerbackend/source/pchmanagerserver.cpp
@@ -41,6 +41,7 @@
 #include <utils/smallstring.h>
 
 #include <QApplication>
+#include <QDirIterator>
 
 #include <algorithm>
 
@@ -50,12 +51,14 @@ PchManagerServer::PchManagerServer(ClangPathWatcherInterface &fileSystemWatcher,
                                    PchTaskGeneratorInterface &pchTaskGenerator,
                                    ProjectPartsManagerInterface &projectParts,
                                    GeneratedFilesInterface &generatedFiles,
-                                   BuildDependenciesStorageInterface &buildDependenciesStorage)
+                                   BuildDependenciesStorageInterface &buildDependenciesStorage,
+                                   FilePathCachingInterface &filePathCache)
     : m_fileSystemWatcher(fileSystemWatcher)
     , m_pchTaskGenerator(pchTaskGenerator)
     , m_projectPartsManager(projectParts)
     , m_generatedFiles(generatedFiles)
     , m_buildDependenciesStorage(buildDependenciesStorage)
+    , m_filePathCache(filePathCache)
 {
     m_fileSystemWatcher.setNotifier(this);
 }
@@ -73,10 +76,43 @@ ProjectPartIds toProjectPartIds(const ProjectPartContainers &projectParts)
     });
 }
 
+FilePaths gatherPathsInIncludePaths(const ProjectPartContainers &projectParts)
+{
+    FilePaths filePaths;
+
+    for (const ProjectPartContainer &projectPart : projectParts) {
+        for (const IncludeSearchPath &searchPath : projectPart.projectIncludeSearchPaths) {
+            QDirIterator directoryIterator(QString{searchPath.path},
+                                           {"*.h", "*.hpp"},
+                                           QDir::Files,
+                                           QDirIterator::FollowSymlinks
+                                               | QDirIterator::Subdirectories);
+            while (directoryIterator.hasNext()) {
+                filePaths.emplace_back(directoryIterator.next());
+            }
+        }
+        for (const IncludeSearchPath &searchPath : projectPart.systemIncludeSearchPaths) {
+            QDirIterator directoryIterator(QString{searchPath.path},
+                                           {"*.h", "*.hpp"},
+                                           QDir::Files,
+                                           QDirIterator::FollowSymlinks);
+            while (directoryIterator.hasNext()) {
+                filePaths.emplace_back(directoryIterator.next());
+            }
+        }
+    }
+
+    return filePaths;
+}
+
 } // namespace
 
 void PchManagerServer::updateProjectParts(UpdateProjectPartsMessage &&message)
 {
+    m_filePathCache.populateIfEmpty();
+
+    m_filePathCache.addFilePaths(gatherPathsInIncludePaths(message.projectsParts));
+
     m_toolChainsArgumentsCache.update(message.projectsParts, message.toolChainArguments);
 
     auto upToDateProjectParts = m_projectPartsManager.update(message.takeProjectsParts());
diff --git a/src/tools/clangpchmanagerbackend/source/pchmanagerserver.h b/src/tools/clangpchmanagerbackend/source/pchmanagerserver.h
index c8e5be4de57..7b1187d5f4b 100644
--- a/src/tools/clangpchmanagerbackend/source/pchmanagerserver.h
+++ b/src/tools/clangpchmanagerbackend/source/pchmanagerserver.h
@@ -40,6 +40,7 @@ namespace ClangBackEnd {
 class SourceRangesAndDiagnosticsForQueryMessage;
 class PchTaskGeneratorInterface;
 class BuildDependenciesStorageInterface;
+class FilePathCachingInterface;
 
 class PchManagerServer : public PchManagerServerInterface,
                          public ClangPathWatcherNotifier,
@@ -51,7 +52,8 @@ public:
                      PchTaskGeneratorInterface &pchTaskGenerator,
                      ProjectPartsManagerInterface &projectParts,
                      GeneratedFilesInterface &generatedFiles,
-                     BuildDependenciesStorageInterface &buildDependenciesStorage);
+                     BuildDependenciesStorageInterface &buildDependenciesStorage,
+                     FilePathCachingInterface &filePathCache);
 
     void end() override;
     void updateProjectParts(UpdateProjectPartsMessage &&message) override;
@@ -76,6 +78,7 @@ private:
     GeneratedFilesInterface &m_generatedFiles;
     BuildDependenciesStorageInterface &m_buildDependenciesStorage;
     ToolChainsArgumentsCache m_toolChainsArgumentsCache;
+    FilePathCachingInterface &m_filePathCache;
 };
 
 } // namespace ClangBackEnd
diff --git a/src/tools/clangpchmanagerbackend/source/projectpartsmanager.cpp b/src/tools/clangpchmanagerbackend/source/projectpartsmanager.cpp
index 548dd373ac1..5e8f6fe0ef4 100644
--- a/src/tools/clangpchmanagerbackend/source/projectpartsmanager.cpp
+++ b/src/tools/clangpchmanagerbackend/source/projectpartsmanager.cpp
@@ -56,27 +56,6 @@ namespace {
 
 enum class Change { System, Project, No };
 
-Change changedSourceType(const SourceEntries &sources)
-{
-    Change change = Change::No;
-    for (SourceEntry sourceEntry : sources) {
-        switch (sourceEntry.sourceType) {
-        case SourceType::SystemInclude:
-        case SourceType::TopSystemInclude:
-            return Change::System;
-        case SourceType::ProjectInclude:
-        case SourceType::TopProjectInclude:
-            change = Change::Project;
-            break;
-        case SourceType::Source:
-        case SourceType::UserInclude:
-            break;
-        }
-    }
-
-    return change;
-}
-
 Change changedSourceType(SourceEntry sourceEntry, Change oldChange)
 {
     switch (sourceEntry.sourceType) {
@@ -109,16 +88,6 @@ FilePathIds existingSources(const FilePathIds &sources, const FilePathIds &gener
     return existingSources;
 }
 
-FilePathIds toFilePathIds(const V2::FileContainers &fileContainers,
-                          FilePathCachingInterface &filePathCache)
-{
-    auto filePaths = Utils::transform<std::vector<FilePathView>>(
-        fileContainers,
-        [](const V2::FileContainer &container) { return FilePathView(container.filePath); });
-
-    return filePathCache.filePathIds(filePaths);
-}
-
 } // namespace
 
 ProjectPartsManager::UpToDataProjectParts ProjectPartsManager::update(ProjectPartContainers &&projectsParts)
@@ -175,7 +144,7 @@ ProjectPartsManagerInterface::UpToDataProjectParts ProjectPartsManager::checkDep
 
     auto systemSplit = updateSystemProjectParts.end();
 
-    FilePathIds generatedFiles = toFilePathIds(m_generatedFiles.fileContainers(), m_filePathCache);
+    FilePathIds generatedFiles = m_generatedFiles.filePathIds();
 
     std::vector<IdPaths> watchedIdPaths;
     watchedIdPaths.reserve(upToDateProjectParts.size() * 4);
diff --git a/src/tools/clangrefactoringbackend/source/refactoringserver.cpp b/src/tools/clangrefactoringbackend/source/refactoringserver.cpp
index 2f79ae31cc8..b86a93ad326 100644
--- a/src/tools/clangrefactoringbackend/source/refactoringserver.cpp
+++ b/src/tools/clangrefactoringbackend/source/refactoringserver.cpp
@@ -81,6 +81,7 @@ void RefactoringServer::requestSourceRangesForQueryMessage(RequestSourceRangesFo
 
 void RefactoringServer::updateProjectParts(UpdateProjectPartsMessage &&message)
 {
+    m_filePathCache.populateIfEmpty();
     m_symbolIndexing.updateProjectParts(message.takeProjectsParts());
 }
 
diff --git a/src/tools/clangrefactoringbackend/source/symbolindexertaskqueue.h b/src/tools/clangrefactoringbackend/source/symbolindexertaskqueue.h
index 1f15f2ffaa0..aa74fb833b7 100644
--- a/src/tools/clangrefactoringbackend/source/symbolindexertaskqueue.h
+++ b/src/tools/clangrefactoringbackend/source/symbolindexertaskqueue.h
@@ -57,7 +57,7 @@ public:
         , m_database(database)
     {}
 
-    void addOrUpdateTasks(std::vector<SymbolIndexerTask> &&tasks)
+    void addOrUpdateTasks(std::vector<SymbolIndexerTask> &&tasks) override
     {
         auto merge = [] (SymbolIndexerTask &&first, SymbolIndexerTask &&second) {
             first.callable = std::move(second.callable);
@@ -71,7 +71,7 @@ public:
 
         m_progressCounter.addTotal(int(m_tasks.size() - oldSize));
     }
-    void removeTasks(const std::vector<int> &projectPartIds)
+    void removeTasks(const ProjectPartIds &projectPartIds) override
     {
         auto shouldBeRemoved = [&] (const SymbolIndexerTask& task) {
             return std::binary_search(projectPartIds.begin(), projectPartIds.end(), task.projectPartId);
@@ -91,7 +91,7 @@ public:
         return m_tasks;
     }
 
-    void processEntries()
+    void processEntries() override
     {
         auto slotUsage = m_symbolIndexerScheduler.slotUsage();
         uint taskCount = slotUsage.free;
diff --git a/src/tools/clangrefactoringbackend/source/symbolindexertaskqueueinterface.h b/src/tools/clangrefactoringbackend/source/symbolindexertaskqueueinterface.h
index dfcc78bd235..3c5bc3479f9 100644
--- a/src/tools/clangrefactoringbackend/source/symbolindexertaskqueueinterface.h
+++ b/src/tools/clangrefactoringbackend/source/symbolindexertaskqueueinterface.h
@@ -27,6 +27,8 @@
 
 #include <queueinterface.h>
 
+#include <projectpartid.h>
+
 #include <utils/smallstringvector.h>
 
 namespace ClangBackEnd {
@@ -38,8 +40,8 @@ class SymbolIndexerTaskQueueInterface : public QueueInterface
 public:
     virtual void addOrUpdateTasks(std::vector<SymbolIndexerTask> &&tasks) = 0
     /* [[expects: std::is_sorted(tasks)]] */;
-    virtual void removeTasks(const std::vector<int> &projectPartIds) = 0
-    /* [[expects: std::is_sorted(projectPartIds)]] */;
+    virtual void removeTasks(const ProjectPartIds &projectPartIds) = 0
+        /* [[expects: std::is_sorted(projectPartIds)]] */;
 
 protected:
     ~SymbolIndexerTaskQueueInterface() = default;
diff --git a/tests/unit/unittest/builddependencycollector-test.cpp b/tests/unit/unittest/builddependencycollector-test.cpp
index 352a60f1def..7bfe6de4cca 100644
--- a/tests/unit/unittest/builddependencycollector-test.cpp
+++ b/tests/unit/unittest/builddependencycollector-test.cpp
@@ -106,6 +106,7 @@ protected:
 
         collector.addUnsavedFiles(
             {{{TESTDATA_DIR, "BuildDependencyCollector/project/generated_file.h"},
+              id(TESTDATA_DIR "/BuildDependencyCollector/project/generated_file.h"),
               "#pragma once",
               {}}});
 
@@ -741,6 +742,7 @@ TEST_F(BuildDependencyCollector, GeneratedFile)
 {
     generatedFiles.update(
         {{TESTDATA_DIR "/builddependencycollector/project/generated/generated_file.h",
+          id(TESTDATA_DIR "/builddependencycollector/project/generated/generated_file.h"),
           "#pragma once"}});
     emptyCollector.addFile(id(TESTDATA_DIR "/builddependencycollector/project/main6.cpp"),
                            {"cc",
@@ -754,9 +756,9 @@ TEST_F(BuildDependencyCollector, GeneratedFile)
 
     emptyCollector.collect();
 
-    ASSERT_THAT(
-        emptyCollector.sourceEntries(),
-        ElementsAre(HasSource(id(TESTDATA_DIR "/builddependencycollector/project/main6.cpp"),
+    ASSERT_THAT(emptyCollector.sourceEntries(),
+                UnorderedElementsAre(
+                    HasSource(id(TESTDATA_DIR "/builddependencycollector/project/main6.cpp"),
                               SourceType::Source),
                     HasSource(id(TESTDATA_DIR
                                  "/builddependencycollector/project/generated/generated_file.h"),
@@ -783,8 +785,9 @@ TEST_F(BuildDependencyCollector, Create)
 {
     using ClangBackEnd::IncludeSearchPathType;
     ClangBackEnd::BuildDependencyCollector collector{filePathCache, generatedFiles, environment};
-    generatedFiles.update(
-        {{TESTDATA_DIR "/builddependencycollector/project/generated_file.h", "#pragma once"}});
+    generatedFiles.update({{TESTDATA_DIR "/builddependencycollector/project/generated_file.h",
+                            id(TESTDATA_DIR "/builddependencycollector/project/generated_file.h"),
+                            "#pragma once"}});
     ClangBackEnd::ProjectPartContainer projectPart{
         1,
         {},
diff --git a/tests/unit/unittest/clangquery-test.cpp b/tests/unit/unittest/clangquery-test.cpp
index 77a049210b7..f17d4166138 100644
--- a/tests/unit/unittest/clangquery-test.cpp
+++ b/tests/unit/unittest/clangquery-test.cpp
@@ -40,6 +40,7 @@
 #include <mutex>
 
 using ClangBackEnd::ClangQuery;
+using ClangBackEnd::FilePath;
 using ClangBackEnd::FilePathCaching;
 using ClangBackEnd::RefactoringDatabaseInitializer;
 
@@ -98,7 +99,11 @@ TEST_F(ClangQuerySlowTest, SourceRangeInUnsavedFileDeclarationRange)
                   "#include \"unsaved.h\"",
                   {"cc", "-std=c++14"});
     query.setQuery("functionDecl()");
-    ClangBackEnd::V2::FileContainer unsavedFile{{TESTDATA_DIR, "unsaved.h"}, "void unsaved();", {}};
+    ClangBackEnd::V2::FileContainer unsavedFile{{TESTDATA_DIR, "unsaved.h"},
+                                                filePathCache.filePathId(
+                                                    FilePath{TESTDATA_DIR, "unsaved.h"}),
+                                                "void unsaved();",
+                                                {}};
     query.addUnsavedFiles({unsavedFile});
 
     query.findLocations();
@@ -125,6 +130,8 @@ TEST_F(ClangQuerySlowTest, DISABLED_SourceRangeInUnsavedFileDeclarationRangeOver
     query.addFile({TESTDATA_DIR "/query_simplefunction.cpp"}, "void f() {}", {"cc", "-std=c++14"});
     query.setQuery("functionDecl()");
     ClangBackEnd::V2::FileContainer unsavedFile{{TESTDATA_DIR "/query_simplefunction.cpp"},
+                                                filePathCache.filePathId(
+                                                    FilePath{TESTDATA_DIR, "query_simplefunction.cpp"}),
                                                 "void unsaved();",
                                                 {}};
     query.addUnsavedFiles({unsavedFile});
diff --git a/tests/unit/unittest/clangquerygatherer-test.cpp b/tests/unit/unittest/clangquerygatherer-test.cpp
index 3b5f9239fed..c301af4ad05 100644
--- a/tests/unit/unittest/clangquerygatherer-test.cpp
+++ b/tests/unit/unittest/clangquerygatherer-test.cpp
@@ -59,10 +59,10 @@ using testing::SizeIs;
 using testing::UnorderedElementsAre;
 using testing::_;
 
-using ClangBackEnd::V2::FileContainer;
+using ClangBackEnd::FilePath;
+using ClangBackEnd::SourceRangesContainer;
 using ClangBackEnd::SourceRangesForQueryMessage;
-using ClangBackEnd::SourceRangesContainer;
-using ClangBackEnd::SourceRangesContainer;
+using ClangBackEnd::V2::FileContainer;
 
 MATCHER_P2(Contains, line, column,
            std::string(negation ? "isn't " : "is ")
@@ -86,22 +86,20 @@ protected:
     ClangBackEnd::FilePathCaching filePathCache{database};
     Utils::SmallString sourceContent{"#include \"query_simplefunction.h\"\nvoid f() {}"};
     FileContainer source{{TESTDATA_DIR, "query_simplefunction.cpp"},
+                         filePathCache.filePathId(FilePath{TESTDATA_DIR, "query_simplefunction.cpp"}),
                          sourceContent.clone(),
-                         {"cc",
-                          "-I",
-                          TESTDATA_DIR}};
+                         {"cc", "-I", TESTDATA_DIR}};
     FileContainer source2{{TESTDATA_DIR, "query_simplefunction2.cpp"},
+                          filePathCache.filePathId(FilePath{TESTDATA_DIR, "query_simplefunction2.cpp"}),
                           {},
-                          {"cc",
-                           "-I",
-                           TESTDATA_DIR}};
+                          {"cc", "-I", TESTDATA_DIR}};
     FileContainer source3{{TESTDATA_DIR, "query_simplefunction3.cpp"},
+                          filePathCache.filePathId(FilePath{TESTDATA_DIR, "query_simplefunction3.cpp"}),
                           {},
-                          {"cc",
-                           "-I",
-                           TESTDATA_DIR}};
+                          {"cc", "-I", TESTDATA_DIR}};
     Utils::SmallString unsavedContent{"void f();"};
     FileContainer unsaved{{TESTDATA_DIR, "query_simplefunction.h"},
+                          filePathCache.filePathId(FilePath{TESTDATA_DIR, "query_simplefunction.h"}),
                           unsavedContent.clone(),
                           {}};
     Utils::SmallString query{"functionDecl()"};
diff --git a/tests/unit/unittest/clangqueryprojectfindfilter-test.cpp b/tests/unit/unittest/clangqueryprojectfindfilter-test.cpp
index 39819809029..65169cb745f 100644
--- a/tests/unit/unittest/clangqueryprojectfindfilter-test.cpp
+++ b/tests/unit/unittest/clangqueryprojectfindfilter-test.cpp
@@ -122,9 +122,7 @@ protected:
     QString unsavedDocumentContent{"void f();"};
     std::vector<Utils::SmallStringVector> commandLines;
     std::vector<CppTools::ProjectPart::Ptr> projectsParts;
-    ClangBackEnd::V2::FileContainer unsavedContent{{"/path/to", "unsaved.cpp"},
-                                                  "void f();",
-                                                  {}};
+    ClangBackEnd::V2::FileContainer unsavedContent{{"/path/to", "unsaved.cpp"}, 1, "void f();", {}};
     ProjectExplorer::Project project;
 };
 
@@ -186,17 +184,12 @@ TEST_F(ClangQueryProjectFindFilter, FindAllIsSettingExprectedResultCountInTheRef
 
 TEST_F(ClangQueryProjectFindFilter, FindAllIsCallingRequestSourceRangesAndDiagnosticsForQueryMessage)
 {
-    ClangBackEnd::RequestSourceRangesForQueryMessage message(findDeclQueryText,
-                                                             {{{"/path/to", "file1.h"},
-                                                               "",
-                                                               commandLines[0].clone()},
-                                                              {{"/path/to", "file1.cpp"},
-                                                               "",
-                                                               commandLines[1].clone()},
-                                                              {{"/path/to", "file2.cpp"},
-                                                               "",
-                                                               commandLines[2].clone()}},
-                                                             {unsavedContent.clone()});
+    ClangBackEnd::RequestSourceRangesForQueryMessage message(
+        findDeclQueryText,
+        {{{"/path/to", "file1.h"}, 1, "", commandLines[0].clone()},
+         {{"/path/to", "file1.cpp"}, 2, "", commandLines[1].clone()},
+         {{"/path/to", "file2.cpp"}, 3, "", commandLines[2].clone()}},
+        {unsavedContent.clone()});
 
     EXPECT_CALL(mockRefactoringServer, requestSourceRangesForQueryMessage(message));
 
diff --git a/tests/unit/unittest/filepathcache-test.cpp b/tests/unit/unittest/filepathcache-test.cpp
index 789eb664511..95557961161 100644
--- a/tests/unit/unittest/filepathcache-test.cpp
+++ b/tests/unit/unittest/filepathcache-test.cpp
@@ -79,6 +79,7 @@ protected:
     NiceMock<MockFilePathStorage> mockStorage{mockDatabase};
     Cache cache{mockStorage};
     NiceMock<MockFilePathStorage> mockStorageFilled{mockDatabase};
+    Cache cacheNotFilled{mockStorageFilled};
 };
 
 TEST_F(FilePathCache, FilePathIdWithOutAnyEntryCallDirectoryId)
@@ -439,4 +440,51 @@ TEST_F(FilePathCache, UseTransactionIfAddingFilesOnlyInAddFilePathsCalls)
 
     cacheFilled.addFilePaths(FilePathViews{"/path/to/file.h"});
 }
+
+TEST_F(FilePathCache, GetFileIdInAfterPopulateIfEmpty)
+{
+    cacheNotFilled.populateIfEmpty();
+
+    auto id = cacheNotFilled.filePathId("/path2/to/file.cpp");
+
+    ASSERT_THAT(id, Eq(72));
+}
+
+TEST_F(FilePathCache, DontPopulateIfNotEmpty)
+{
+    cacheNotFilled.filePathId("/path/to/file.cpp");
+    cacheNotFilled.populateIfEmpty();
+
+    auto id = cacheNotFilled.filePathId("/path2/to/file.cpp");
+
+    ASSERT_FALSE(id.isValid());
+}
+
+TEST_F(FilePathCache, GetDirectoryIdAfterPopulateIfEmpty)
+{
+    cacheNotFilled.populateIfEmpty();
+
+    auto id = cacheNotFilled.directoryPathId(42);
+
+    ASSERT_THAT(id, Eq(5));
+}
+
+TEST_F(FilePathCache, GetDirectoryPathAfterPopulateIfEmpty)
+{
+    cacheNotFilled.populateIfEmpty();
+
+    auto path = cacheNotFilled.directoryPath(5);
+
+    ASSERT_THAT(path, Eq("/path/to"));
+}
+
+TEST_F(FilePathCache, GetFilePathAfterPopulateIfEmptye)
+{
+    cacheNotFilled.populateIfEmpty();
+
+    auto path = cacheNotFilled.filePath(42);
+
+    ASSERT_THAT(path, Eq("/path/to/file.cpp"));
+}
+
 } // namespace
diff --git a/tests/unit/unittest/generatedfiles-test.cpp b/tests/unit/unittest/generatedfiles-test.cpp
index 9db9c4b0aee..8e5a34ffd71 100644
--- a/tests/unit/unittest/generatedfiles-test.cpp
+++ b/tests/unit/unittest/generatedfiles-test.cpp
@@ -35,12 +35,12 @@ using ClangBackEnd::V2::FileContainers;
 class GeneratedFiles : public testing::Test
 {
 protected:
-    FileContainer file1{"/file1", "content1"};
-    FileContainer file1b{"/file1", "content1b"};
-    FileContainer file2{"/file2", "content2"};
-    FileContainer file2b{"/file2", "content2b"};
-    FileContainer file3{"/file3", "content3"};
-    FileContainer file4{"/file4", "content4"};
+    FileContainer file1{"/file1", 1, "content1"};
+    FileContainer file1b{"/file1", 1, "content1b"};
+    FileContainer file2{"/file2", 2, "content2"};
+    FileContainer file2b{"/file2", 2, "content2b"};
+    FileContainer file3{"/file3", 3, "content3"};
+    FileContainer file4{"/file4", 4, "content4"};
     ClangBackEnd::GeneratedFiles generatedFiles;
 };
 
@@ -76,7 +76,7 @@ TEST_F(GeneratedFiles, IsValidForNoGeneratedFiles)
 
 TEST_F(GeneratedFiles, IsNotValidIfFilesWithNotContentExists)
 {
-    generatedFiles.update({{"/file2", ""}});
+    generatedFiles.update({{"/file2", 2, ""}});
 
     ASSERT_FALSE(generatedFiles.isValid());
 }
@@ -86,4 +86,15 @@ TEST_F(GeneratedFiles, IsValidIfAllFilesHasContent)
     generatedFiles.update({file1, file2, file3, file4});
 
     ASSERT_TRUE(generatedFiles.isValid());
-}}
+}
+
+TEST_F(GeneratedFiles, GetFilePathIds)
+{
+    generatedFiles.update({file3, file2, file1, file4});
+
+    auto ids = generatedFiles.filePathIds();
+
+    ASSERT_THAT(ids, ElementsAre(1, 2, 3, 4));
+}
+
+} // namespace
diff --git a/tests/unit/unittest/gtest-creator-printing.h b/tests/unit/unittest/gtest-creator-printing.h
index b533186739d..624288ee98d 100644
--- a/tests/unit/unittest/gtest-creator-printing.h
+++ b/tests/unit/unittest/gtest-creator-printing.h
@@ -106,7 +106,7 @@ void PrintTo(Utils::SmallStringView text, ::std::ostream *os);
 void PrintTo(const Utils::SmallString &text, ::std::ostream *os);
 void PrintTo(const Utils::PathString &text, ::std::ostream *os);
 
-} // namespace ProjectExplorer
+} // namespace Utils
 
 namespace ClangBackEnd {
 class SourceLocationEntry;
diff --git a/tests/unit/unittest/mockfilepathcaching.h b/tests/unit/unittest/mockfilepathcaching.h
index bec249a5a53..155aa491c97 100644
--- a/tests/unit/unittest/mockfilepathcaching.h
+++ b/tests/unit/unittest/mockfilepathcaching.h
@@ -43,4 +43,5 @@ public:
     MOCK_CONST_METHOD1(directoryPathId,
                        ClangBackEnd::DirectoryPathId(ClangBackEnd::FilePathId filePathId));
     MOCK_METHOD1(addFilePaths, void(const ClangBackEnd::FilePaths &filePaths));
+    MOCK_METHOD0(populateIfEmpty, void());
 };
diff --git a/tests/unit/unittest/mockgeneratedfiles.h b/tests/unit/unittest/mockgeneratedfiles.h
index 75b182355c2..481747c27ff 100644
--- a/tests/unit/unittest/mockgeneratedfiles.h
+++ b/tests/unit/unittest/mockgeneratedfiles.h
@@ -38,6 +38,7 @@ public:
                  void (const ClangBackEnd::FilePaths &filePaths));
     MOCK_CONST_METHOD0(fileContainers,
                        const ClangBackEnd::V2::FileContainers &());
+    MOCK_CONST_METHOD0(filePathIds, ClangBackEnd::FilePathIds());
     MOCK_CONST_METHOD0(isValid, bool());
 
     void update(ClangBackEnd::V2::FileContainers &&fileContainers)
diff --git a/tests/unit/unittest/mockprojectpartsstorage.h b/tests/unit/unittest/mockprojectpartsstorage.h
index e8dcbc94b2e..cdca4ef78e3 100644
--- a/tests/unit/unittest/mockprojectpartsstorage.h
+++ b/tests/unit/unittest/mockprojectpartsstorage.h
@@ -36,8 +36,11 @@ public:
     MOCK_CONST_METHOD1(
         fetchProjectParts,
         ClangBackEnd::ProjectPartContainers(const ClangBackEnd::ProjectPartIds &projectPartIds));
+    MOCK_CONST_METHOD0(fetchAllProjectPartNamesAndIds, ClangBackEnd::Internal::ProjectPartNameIds());
     MOCK_CONST_METHOD1(fetchProjectPartId,
                        ClangBackEnd::ProjectPartId(Utils::SmallStringView projectPartName));
+    MOCK_CONST_METHOD1(fetchProjectPartIdUnguarded,
+                       ClangBackEnd::ProjectPartId(Utils::SmallStringView projectPartName));
     MOCK_CONST_METHOD1(fetchProjectPartName,
                        Utils::PathString(ClangBackEnd::ProjectPartId projectPartId));
     MOCK_METHOD8(updateProjectPart,
diff --git a/tests/unit/unittest/mocksqlitereadstatement.cpp b/tests/unit/unittest/mocksqlitereadstatement.cpp
index 9a949e4b0a9..0a63f3c284e 100644
--- a/tests/unit/unittest/mocksqlitereadstatement.cpp
+++ b/tests/unit/unittest/mocksqlitereadstatement.cpp
@@ -109,6 +109,12 @@ std::vector<Sources::Source> MockSqliteReadStatement::values<Sources::Source, 3>
     return valuesReturnStdVectorSource(reserveSize);
 }
 
+template<>
+ProjectPartNameIds MockSqliteReadStatement::values<ProjectPartNameId, 2>(std::size_t reserveSize)
+{
+    return valuesReturnProjectPartNameIds(reserveSize);
+}
+
 template <>
 Utils::optional<int>
 MockSqliteReadStatement::value<int>(const Utils::SmallStringView &text)
diff --git a/tests/unit/unittest/mocksqlitereadstatement.h b/tests/unit/unittest/mocksqlitereadstatement.h
index 8ebcb6e13b9..0048fd62760 100644
--- a/tests/unit/unittest/mocksqlitereadstatement.h
+++ b/tests/unit/unittest/mocksqlitereadstatement.h
@@ -34,6 +34,7 @@
 #include <projectpartartefact.h>
 #include <projectpartcontainer.h>
 #include <projectpartpch.h>
+#include <projectpartstoragestructs.h>
 #include <sourceentry.h>
 #include <stringcachefwd.h>
 #include <symbol.h>
@@ -59,6 +60,8 @@ using std::int64_t;
 namespace Sources = ClangBackEnd::Sources;
 using ClangBackEnd::PrecompiledHeaderTimeStamps;
 using ClangBackEnd::UsedMacros;
+using ClangBackEnd::Internal::ProjectPartNameId;
+using ClangBackEnd::Internal::ProjectPartNameIds;
 using ClangRefactoring::Symbol;
 using ClangRefactoring::Symbols;
 
@@ -91,6 +94,8 @@ public:
 
     MOCK_METHOD2(valuesReturnFilePathIds, FilePathIds(std::size_t, int));
 
+    MOCK_METHOD1(valuesReturnProjectPartNameIds, ProjectPartNameIds(std::size_t));
+
     MOCK_METHOD1(valueReturnInt32, Utils::optional<int>(Utils::SmallStringView));
 
     MOCK_METHOD2(valueReturnInt32, Utils::optional<int>(int, Utils::SmallStringView));
@@ -226,9 +231,11 @@ std::vector<Sources::Directory> MockSqliteReadStatement::values<Sources::Directo
 template<>
 std::vector<Sources::Source> MockSqliteReadStatement::values<Sources::Source, 3>(std::size_t reserveSize);
 
-template <>
-Utils::optional<int>
-MockSqliteReadStatement::value<int>(const Utils::SmallStringView&);
+template<>
+ProjectPartNameIds MockSqliteReadStatement::values<ProjectPartNameId, 2>(std::size_t reserveSize);
+
+template<>
+Utils::optional<int> MockSqliteReadStatement::value<int>(const Utils::SmallStringView &);
 
 template <>
 Utils::optional<int>
diff --git a/tests/unit/unittest/mocksymbolindexertaskqueue.h b/tests/unit/unittest/mocksymbolindexertaskqueue.h
index 7fb0d3f0bd7..cef60ac7765 100644
--- a/tests/unit/unittest/mocksymbolindexertaskqueue.h
+++ b/tests/unit/unittest/mocksymbolindexertaskqueue.h
@@ -34,7 +34,6 @@ class MockSymbolIndexerTaskQueue : public ClangBackEnd::SymbolIndexerTaskQueueIn
 public:
     MOCK_METHOD1(addOrUpdateTasks,
                  void (std::vector<ClangBackEnd::SymbolIndexerTask> &&tasks));
-    MOCK_METHOD1(removeTasks,
-                 void (const std::vector<int> &projectPartIds));
+    MOCK_METHOD1(removeTasks, void(const ClangBackEnd::ProjectPartIds &projectPartIds));
     MOCK_METHOD0(processEntries, void());
 };
diff --git a/tests/unit/unittest/pchcreator-test.cpp b/tests/unit/unittest/pchcreator-test.cpp
index e97f60b9f50..ad5b57b4f52 100644
--- a/tests/unit/unittest/pchcreator-test.cpp
+++ b/tests/unit/unittest/pchcreator-test.cpp
@@ -91,7 +91,7 @@ protected:
 
     ClangBackEnd::FilePathId id(ClangBackEnd::FilePathView path)
     {
-        return creator.filePathCache().filePathId(path);
+        return filePathCache.filePathId(path);
     }
 
     FilePathIds sorted(FilePathIds &&filePathIds)
@@ -104,17 +104,17 @@ protected:
 protected:
     Sqlite::Database database{":memory:", Sqlite::JournalMode::Memory};
     ClangBackEnd::RefactoringDatabaseInitializer<Sqlite::Database> databaseInitializer{database};
+    ClangBackEnd::FilePathCaching filePathCache{database};
     FilePath main1Path = TESTDATA_DIR "/builddependencycollector/project/main3.cpp";
     FilePath main2Path = TESTDATA_DIR "/builddependencycollector/project/main2.cpp";
     FilePath header1Path = TESTDATA_DIR "/builddependencycollector/project/header1.h";
     FilePath header2Path = TESTDATA_DIR "/builddependencycollector/project/header2.h";
     FilePath generatedFilePath = TESTDATA_DIR "/builddependencycollector/project/generated_file.h";
     TestEnvironment environment;
-    FileContainer generatedFile{generatedFilePath.clone(), "#pragma once", {}};
+    FileContainer generatedFile{generatedFilePath.clone(), id(generatedFilePath), "#pragma once", {}};
     NiceMock<MockPchManagerClient> mockPchManagerClient;
     NiceMock<MockClangPathWatcher> mockClangPathWatcher;
     NiceMock<MockBuildDependenciesStorage> mockBuildDependenciesStorage;
-    ClangBackEnd::FilePathCaching filePathCache{database};
     ClangBackEnd::PchCreator creator{environment,
                                      filePathCache,
                                      mockPchManagerClient,
diff --git a/tests/unit/unittest/pchmanagerclientserverinprocess-test.cpp b/tests/unit/unittest/pchmanagerclientserverinprocess-test.cpp
index 194f52afd3b..e468521a545 100644
--- a/tests/unit/unittest/pchmanagerclientserverinprocess-test.cpp
+++ b/tests/unit/unittest/pchmanagerclientserverinprocess-test.cpp
@@ -117,7 +117,7 @@ TEST_F(PchManagerClientServerInProcess, SendUpdateProjectPartsMessage)
 
 TEST_F(PchManagerClientServerInProcess, SendUpdateGeneratedFilesMessage)
 {
-    FileContainer fileContainer{{"/path/to/", "file"}, "content", {}};
+    FileContainer fileContainer{{"/path/to/", "file"}, 1, "content", {}};
     UpdateGeneratedFilesMessage message{{fileContainer}};
 
     EXPECT_CALL(mockPchManagerServer, updateGeneratedFiles(message));
diff --git a/tests/unit/unittest/pchmanagerserver-test.cpp b/tests/unit/unittest/pchmanagerserver-test.cpp
index d7e6c492f9a..bf14b628b8d 100644
--- a/tests/unit/unittest/pchmanagerserver-test.cpp
+++ b/tests/unit/unittest/pchmanagerserver-test.cpp
@@ -27,6 +27,7 @@
 
 #include "mockbuilddependenciesstorage.h"
 #include "mockclangpathwatcher.h"
+#include "mockfilepathcaching.h"
 #include "mockgeneratedfiles.h"
 #include "mockpchmanagerclient.h"
 #include "mockpchtaskgenerator.h"
@@ -77,11 +78,13 @@ protected:
     Sqlite::Database database{":memory:", Sqlite::JournalMode::Memory};
     ClangBackEnd::RefactoringDatabaseInitializer<Sqlite::Database> initializer{database};
     ClangBackEnd::FilePathCaching filePathCache{database};
+    NiceMock<MockFilePathCaching> mockFilePathCache;
     ClangBackEnd::PchManagerServer server{mockClangPathWatcher,
                                           mockPchTaskGenerator,
                                           mockProjectPartsManager,
                                           mockGeneratedFiles,
-                                          mockBuildDependenciesStorage};
+                                          mockBuildDependenciesStorage,
+                                          mockFilePathCache};
     NiceMock<MockPchManagerClient> mockPchManagerClient;
     ClangBackEnd::ProjectPartId projectPartId1{1};
     ClangBackEnd::ProjectPartId projectPartId2{2};
@@ -98,7 +101,7 @@ protected:
         projectPartId1,
         {"-I", TESTDATA_DIR, "-Wno-pragma-once-outside-header"},
         {{"DEFINE", "1", 1}},
-        {{"/includes", 1, ClangBackEnd::IncludeSearchPathType::BuiltIn}},
+        {{TESTDATA_DIR "/symbolscollector/include", 1, ClangBackEnd::IncludeSearchPathType::BuiltIn}},
         {{"/project/includes", 1, ClangBackEnd::IncludeSearchPathType::User}},
         {id(header1Path)},
         {id(main1Path)},
@@ -110,7 +113,7 @@ protected:
         {"-x", "c++-header", "-Wno-pragma-once-outside-header"},
         {{"DEFINE", "1", 1}},
         {{"/includes", 1, ClangBackEnd::IncludeSearchPathType::BuiltIn}},
-        {{"/project/includes", 1, ClangBackEnd::IncludeSearchPathType::User}},
+        {{TESTDATA_DIR "/builddependencycollector", 1, ClangBackEnd::IncludeSearchPathType::User}},
         {id(header2Path)},
         {id(main2Path)},
         Utils::Language::C,
@@ -165,7 +168,7 @@ protected:
     std::vector<ProjectPartContainer> projectParts2{projectPart2};
     std::vector<ProjectPartContainer> projectParts3{projectPart3};
     std::vector<ProjectPartContainer> projectParts4{projectPart3, projectPart4};
-    FileContainer generatedFile{{"/path/to/", "file"}, "content", {}};
+    FileContainer generatedFile{{"/path/to/", "file"}, id("/path/to/file"), "content", {}};
     ClangBackEnd::UpdateProjectPartsMessage updateProjectPartsMessage{
         Utils::clone(projectParts), {"toolChainArgument"}};
     ClangBackEnd::RemoveProjectPartsMessage removeProjectPartsMessage{
@@ -226,7 +229,8 @@ TEST_F(PchManagerServer, SetPathWatcherNotifier)
                                           mockPchTaskGenerator,
                                           mockProjectPartsManager,
                                           mockGeneratedFiles,
-                                          mockBuildDependenciesStorage};
+                                          mockBuildDependenciesStorage,
+                                          filePathCache};
 }
 
 TEST_F(PchManagerServer, UpdateProjectPartQueueByPathIds)
@@ -419,4 +423,20 @@ TEST_F(PchManagerServer, SentUpToDateProjectPartIdsToClient)
 
     server.updateProjectParts(updateProjectPartsMessage.clone());
 }
+
+TEST_F(PchManagerServer, AddingIncludesToFileCacheForProjectUpdates)
+{
+    InSequence s;
+
+    EXPECT_CALL(mockFilePathCache, populateIfEmpty());
+    EXPECT_CALL(mockFilePathCache,
+                addFilePaths(AllOf(
+                    Contains(Eq(TESTDATA_DIR "/symbolscollector/include/unmodified_header.h")),
+                    Contains(Eq(TESTDATA_DIR "/symbolscollector/include/unmodified_header2.h")),
+                    Contains(Eq(TESTDATA_DIR "/builddependencycollector/project/header2.h")),
+                    Contains(Eq(TESTDATA_DIR "/builddependencycollector/external/external3.h")))));
+    EXPECT_CALL(mockProjectPartsManager, update(_));
+
+    server.updateProjectParts(updateProjectPartsMessage.clone());
+}
 } // namespace
diff --git a/tests/unit/unittest/projectpartsstorage-test.cpp b/tests/unit/unittest/projectpartsstorage-test.cpp
index 6c887ca3f06..b67cd5a37c4 100644
--- a/tests/unit/unittest/projectpartsstorage-test.cpp
+++ b/tests/unit/unittest/projectpartsstorage-test.cpp
@@ -29,11 +29,13 @@
 
 #include <builddependenciesstorage.h>
 #include <projectpartsstorage.h>
+#include <projectpartstoragestructs.h>
 #include <refactoringdatabaseinitializer.h>
 #include <sqlitedatabase.h>
 #include <sqlitereadstatement.h>
 #include <sqlitewritestatement.h>
 #include <symbolstorage.h>
+
 namespace {
 
 using ClangBackEnd::FilePathId;
@@ -107,6 +109,7 @@ protected:
     MockSqliteReadStatement &fetchProjectPrecompiledHeaderPathStatement = storage.fetchProjectPrecompiledHeaderBuildTimeStatement;
     MockSqliteReadStatement &fetchProjectPrecompiledHeaderBuildTimeStatement = storage.fetchProjectPrecompiledHeaderBuildTimeStatement;
     MockSqliteWriteStatement &resetDependentIndexingTimeStampsStatement = storage.resetDependentIndexingTimeStampsStatement;
+    MockSqliteReadStatement &fetchAllProjectPartNamesAndIdsStatement = storage.fetchAllProjectPartNamesAndIdsStatement;
     IncludeSearchPaths systemIncludeSearchPaths{{"/includes", 1, IncludeSearchPathType::BuiltIn},
                                                 {"/other/includes", 2, IncludeSearchPathType::System}};
     IncludeSearchPaths projectIncludeSearchPaths{{"/project/includes", 1, IncludeSearchPathType::User},
@@ -124,6 +127,7 @@ protected:
                                                Utils::Language::Cxx,
                                                Utils::LanguageVersion::CXX11,
                                                Utils::LanguageExtension::None};
+    ClangBackEnd::Internal::ProjectPartNameIds projectPartNameIds{{"projectPartName", 2}};
 };
 
 TEST_F(ProjectPartsStorage, CallsFetchProjectIdWithNonExistingProjectPartName)
@@ -139,6 +143,17 @@ TEST_F(ProjectPartsStorage, CallsFetchProjectIdWithNonExistingProjectPartName)
     storage.fetchProjectPartId("test");
 }
 
+TEST_F(ProjectPartsStorage, CallsFetchProjectIdWithNonExistingProjectPartNameUnguarded)
+{
+    InSequence s;
+
+    EXPECT_CALL(fetchProjectPartIdStatement,
+                valueReturnProjectPartId(TypedEq<Utils::SmallStringView>("test")));
+    EXPECT_CALL(insertProjectPartNameStatement, write(TypedEq<Utils::SmallStringView>("test")));
+
+    storage.fetchProjectPartIdUnguarded("test");
+}
+
 TEST_F(ProjectPartsStorage, CallsFetchProjectIdWithExistingProjectPart)
 {
     InSequence s;
@@ -153,6 +168,18 @@ TEST_F(ProjectPartsStorage, CallsFetchProjectIdWithExistingProjectPart)
     storage.fetchProjectPartId("test");
 }
 
+TEST_F(ProjectPartsStorage, CallsFetchProjectIdWithExistingProjectPartUnguarded)
+{
+    InSequence s;
+
+    EXPECT_CALL(fetchProjectPartIdStatement,
+                valueReturnProjectPartId(TypedEq<Utils::SmallStringView>("test")))
+        .WillOnce(Return(Utils::optional<ProjectPartId>{20}));
+    EXPECT_CALL(insertProjectPartNameStatement, write(TypedEq<Utils::SmallStringView>("test"))).Times(0);
+
+    storage.fetchProjectPartIdUnguarded("test");
+}
+
 TEST_F(ProjectPartsStorage, CallsFetchProjectIdWithBusyDatabaset)
 {
     InSequence s;
@@ -184,6 +211,18 @@ TEST_F(ProjectPartsStorage, FetchProjectIdWithNonExistingProjectPartName)
     ASSERT_THAT(id.projectPathId, 21);
 }
 
+TEST_F(ProjectPartsStorage, FetchProjectIdWithNonExistingProjectPartNameUnguarded)
+{
+    ON_CALL(fetchProjectPartIdStatement,
+            valueReturnProjectPartId(TypedEq<Utils::SmallStringView>("test")))
+        .WillByDefault(Return(Utils::optional<ProjectPartId>{}));
+    ON_CALL(mockDatabase, lastInsertedRowId()).WillByDefault(Return(21));
+
+    auto id = storage.fetchProjectPartIdUnguarded("test");
+
+    ASSERT_THAT(id.projectPathId, 21);
+}
+
 TEST_F(ProjectPartsStorage, FetchProjectIdWithNonExistingProjectPartNameAndIsBusy)
 {
     InSequence s;
@@ -211,6 +250,17 @@ TEST_F(ProjectPartsStorage, FetchProjectIdWithExistingProjectPartName)
     ASSERT_THAT(id.projectPathId, 20);
 }
 
+TEST_F(ProjectPartsStorage, FetchProjectIdWithExistingProjectPartNameUnguarded)
+{
+    ON_CALL(fetchProjectPartIdStatement,
+            valueReturnProjectPartId(TypedEq<Utils::SmallStringView>("test")))
+        .WillByDefault(Return(Utils::optional<ProjectPartId>{20}));
+
+    auto id = storage.fetchProjectPartIdUnguarded("test");
+
+    ASSERT_THAT(id.projectPathId, 20);
+}
+
 TEST_F(ProjectPartsStorage, FetchProjectPartName)
 {
     InSequence s;
@@ -418,6 +468,7 @@ TEST_F(ProjectPartsStorage, FetchProjectPartArtefactBySourceIdCallsValueInStatem
 
     storage.fetchProjectPartArtefact(FilePathId{1});
 }
+
 TEST_F(ProjectPartsStorage, FetchProjectPartArtefactBySourceIdReturnArtefact)
 {
     EXPECT_CALL(getProjectPartArtefactsBySourceId, valueReturnProjectPartArtefact(1))
@@ -495,6 +546,34 @@ TEST_F(ProjectPartsStorage, ResetDependentIndexingTimeStampsIsBusy)
     storage.resetIndexingTimeStamps({projectPart1, projectPart2});
 }
 
+TEST_F(ProjectPartsStorage, FetchAllProjectPartNamesAndIdsCalls)
+{
+    InSequence s;
+
+    EXPECT_CALL(mockDatabase, deferredBegin());
+    EXPECT_CALL(fetchAllProjectPartNamesAndIdsStatement, valuesReturnProjectPartNameIds(_))
+        .WillRepeatedly(Return(projectPartNameIds));
+    EXPECT_CALL(mockDatabase, commit());
+
+    storage.fetchAllProjectPartNamesAndIds();
+}
+
+TEST_F(ProjectPartsStorage, FetchAllProjectPartNamesAndIdsCallsIsBusy)
+{
+    InSequence s;
+
+    EXPECT_CALL(mockDatabase, deferredBegin());
+    EXPECT_CALL(fetchAllProjectPartNamesAndIdsStatement, valuesReturnProjectPartNameIds(_))
+        .WillOnce(Throw(Sqlite::StatementIsBusy{""}));
+    EXPECT_CALL(mockDatabase, rollback());
+    EXPECT_CALL(mockDatabase, deferredBegin());
+    EXPECT_CALL(fetchAllProjectPartNamesAndIdsStatement, valuesReturnProjectPartNameIds(_))
+        .WillRepeatedly(Return(projectPartNameIds));
+    EXPECT_CALL(mockDatabase, commit());
+
+    storage.fetchAllProjectPartNamesAndIds();
+}
+
 class ProjectPartsStorageSlow : public testing::Test, public Data
 {
     using Storage = ClangBackEnd::ProjectPartsStorage<Sqlite::Database>;
@@ -530,6 +609,15 @@ TEST_F(ProjectPartsStorageSlow, FetchProjectPartId)
     ASSERT_THAT(first, Eq(second));
 }
 
+TEST_F(ProjectPartsStorageSlow, FetchProjectPartIdUnguarded)
+{
+    auto first = storage.fetchProjectPartId("test");
+
+    auto second = storage.fetchProjectPartIdUnguarded("test");
+
+    ASSERT_THAT(first, Eq(second));
+}
+
 TEST_F(ProjectPartsStorageSlow, FetchProjectParts)
 {
     projectPart1.projectPartId = storage.fetchProjectPartId("project1");
@@ -563,4 +651,16 @@ TEST_F(ProjectPartsStorageSlow, ResetDependentIndexingTimeStamps)
                             SourceTimeStamp{10, 34}));
 }
 
+TEST_F(ProjectPartsStorageSlow, FetchAllProjectPartNamesAndIdsy)
+{
+    using ClangBackEnd::Internal::ProjectPartNameId;
+    auto id = storage.fetchProjectPartId("projectPartName");
+    auto id2 = storage.fetchProjectPartId("projectPartName2");
+
+    auto values = storage.fetchAllProjectPartNamesAndIds();
+
+    ASSERT_THAT(values,
+                UnorderedElementsAre(ProjectPartNameId{"projectPartName", id},
+                                     ProjectPartNameId{"projectPartName2", id2}));
+}
 } // namespace
diff --git a/tests/unit/unittest/projectupdater-test.cpp b/tests/unit/unittest/projectupdater-test.cpp
index 73f5359df09..1b9f271687d 100644
--- a/tests/unit/unittest/projectupdater-test.cpp
+++ b/tests/unit/unittest/projectupdater-test.cpp
@@ -66,10 +66,11 @@ using testing::NiceMock;
 using testing::AnyNumber;
 
 using ClangBackEnd::CompilerMacro;
+using ClangBackEnd::FilePath;
 using ClangBackEnd::IncludeSearchPath;
 using ClangBackEnd::IncludeSearchPathType;
-using ClangBackEnd::V2::FileContainer;
 using ClangBackEnd::ProjectPartContainer;
+using ClangBackEnd::V2::FileContainer;
 using CppTools::CompilerOptionsBuilder;
 using ProjectExplorer::HeaderPath;
 
@@ -182,9 +183,18 @@ protected:
     CppTools::ProjectPart nonBuildingProjectPart;
     ProjectPartContainer expectedContainer;
     ProjectPartContainer expectedContainer2;
-    FileContainer generatedFile{{"/path/to", "header1.h"}, "content", {}};
-    FileContainer generatedFile2{{"/path/to2", "header1.h"}, "content", {}};
-    FileContainer generatedFile3{{"/path/to", "header2.h"}, "content", {}};
+    FileContainer generatedFile{{"/path/to", "header1.h"},
+                                filePathCache.filePathId(FilePath{"/path/to", "header1.h"}),
+                                "content",
+                                {}};
+    FileContainer generatedFile2{{"/path/to2", "header1.h"},
+                                 filePathCache.filePathId(FilePath{"/path/to2", "header1.h"}),
+                                 "content",
+                                 {}};
+    FileContainer generatedFile3{{"/path/to", "header2.h"},
+                                 filePathCache.filePathId(FilePath{"/path/to", "header2.h"}),
+                                 "content",
+                                 {}};
 };
 
 TEST_F(ProjectUpdater, CallUpdateProjectParts)
@@ -271,6 +281,7 @@ TEST_F(ProjectUpdater, CallPrecompiledHeaderRemovedInPchManagerProjectUpdater)
 TEST_F(ProjectUpdater, ConvertProjectPartToProjectPartContainer)
 {
     updater.setExcludedPaths({"/path/to/header1.h"});
+    updater.fetchProjectPartIds({&projectPart});
 
     auto container = updater.toProjectPartContainer(&projectPart);
 
@@ -279,21 +290,23 @@ TEST_F(ProjectUpdater, ConvertProjectPartToProjectPartContainer)
 
 TEST_F(ProjectUpdater, ConvertProjectPartToProjectPartContainersHaveSameSizeLikeProjectParts)
 {
+    updater.fetchProjectPartIds({&projectPart, &nonBuildingProjectPart});
+
     auto containers = updater.toProjectPartContainers(
         {&projectPart, &projectPart, &nonBuildingProjectPart});
 
     ASSERT_THAT(containers, SizeIs(2));
 }
 
-TEST_F(ProjectUpdater, CallStorageInsideTransaction)
+TEST_F(ProjectUpdater, ProjectPartIdsPrefetchingInsideTransaction)
 {
     InSequence s;
     CppTools::ProjectPart projectPart;
     projectPart.project = &project;
     projectPart.displayName = "project";
     Utils::SmallString projectPartName = projectPart.id();
-    MockSqliteTransactionBackend mockSqliteTransactionBackend;
-    MockProjectPartsStorage mockProjectPartsStorage;
+    NiceMock<MockSqliteTransactionBackend> mockSqliteTransactionBackend;
+    NiceMock<MockProjectPartsStorage> mockProjectPartsStorage;
     ON_CALL(mockProjectPartsStorage, transactionBackend())
         .WillByDefault(ReturnRef(mockSqliteTransactionBackend));
     ClangPchManager::ClangIndexingSettingsManager settingsManager;
@@ -302,9 +315,11 @@ TEST_F(ProjectUpdater, CallStorageInsideTransaction)
                                             mockProjectPartsStorage,
                                             settingsManager};
 
-    EXPECT_CALL(mockProjectPartsStorage, fetchProjectPartId(Eq(projectPartName)));
+    EXPECT_CALL(mockSqliteTransactionBackend, deferredBegin());
+    EXPECT_CALL(mockProjectPartsStorage, fetchProjectPartIdUnguarded(Eq(projectPartName)));
+    EXPECT_CALL(mockSqliteTransactionBackend, commit());
 
-    updater.toProjectPartContainers({&projectPart});
+    updater.fetchProjectPartIds({&projectPart});
 }
 
 TEST_F(ProjectUpdater, CreateSortedExcludedPaths)
@@ -476,7 +491,8 @@ TEST_F(ProjectUpdater, AddProjectFilesToFilePathCache)
     NiceMock<MockFilePathCaching> mockFilePathCaching;
     ClangPchManager::ProjectUpdater updater{mockPchManagerServer,
                                             mockFilePathCaching,
-                                            projectPartsStorage};
+                                            projectPartsStorage,
+                                            settingsManager};
 
     EXPECT_CALL(mockFilePathCaching,
                 addFilePaths(UnorderedElementsAre(Eq(headerPaths[0]),
@@ -487,6 +503,39 @@ TEST_F(ProjectUpdater, AddProjectFilesToFilePathCache)
     updater.updateProjectParts({&projectPart}, {});
 }
 
-// test for update many time and get the same id
+TEST_F(ProjectUpdater, FillProjectPartIdCacheAtCreation)
+{
+    NiceMock<MockProjectPartsStorage> mockProjectPartsStorage;
+
+    EXPECT_CALL(mockProjectPartsStorage, fetchAllProjectPartNamesAndIds());
+
+    ClangPchManager::ProjectUpdater updater{mockPchManagerServer,
+                                            filePathCache,
+                                            mockProjectPartsStorage,
+                                            settingsManager};
+}
+
+TEST_F(ProjectUpdater, DontFetchProjectPartIdFromDatabaseIfItIsInCache)
+{
+    projectPart.files.clear();
+    NiceMock<MockSqliteTransactionBackend> mockSqliteTransactionBackend;
+    NiceMock<MockProjectPartsStorage> mockProjectPartsStorage;
+    ON_CALL(mockProjectPartsStorage, transactionBackend())
+        .WillByDefault(ReturnRef(mockSqliteTransactionBackend));
+    ON_CALL(mockProjectPartsStorage, fetchAllProjectPartNamesAndIds())
+        .WillByDefault(Return(
+            ClangBackEnd::Internal::ProjectPartNameIds{{Utils::PathString(projectPart.id()), 55}}));
+    ClangPchManager::ProjectUpdater updater{mockPchManagerServer,
+                                            filePathCache,
+                                            mockProjectPartsStorage,
+                                            settingsManager};
+
+    EXPECT_CALL(mockSqliteTransactionBackend, deferredBegin()).Times(0);
+    EXPECT_CALL(mockProjectPartsStorage, fetchProjectPartId(_)).Times(0);
+    EXPECT_CALL(mockProjectPartsStorage, fetchProjectPartIdUnguarded(_)).Times(0);
+    EXPECT_CALL(mockSqliteTransactionBackend, commit()).Times(0);
+
+    updater.updateProjectParts({&projectPart}, {});
+}
 
 } // namespace
diff --git a/tests/unit/unittest/refactoringclientserverinprocess-test.cpp b/tests/unit/unittest/refactoringclientserverinprocess-test.cpp
index 8b6237bfad8..344eb08f03c 100644
--- a/tests/unit/unittest/refactoringclientserverinprocess-test.cpp
+++ b/tests/unit/unittest/refactoringclientserverinprocess-test.cpp
@@ -129,8 +129,8 @@ TEST_F(RefactoringClientServerInProcess, RequestSourceRangesAndDiagnosticsForQue
 {
     RequestSourceRangesForQueryMessage message{
         "functionDecl()",
-        {{{TESTDATA_DIR, "query_simplefunction.cpp"}, "void f();", {"cc"}, 1}},
-        {{{TESTDATA_DIR, "query_simplefunction.h"}, "void f();", {}, 1}}};
+        {{{TESTDATA_DIR, "query_simplefunction.cpp"}, 1, "void f();", {"cc"}, 1}},
+        {{{TESTDATA_DIR, "query_simplefunction.h"}, 2, "void f();", {}, 1}}};
 
     EXPECT_CALL(mockRefactoringServer, requestSourceRangesForQueryMessage(message));
 
@@ -143,12 +143,13 @@ TEST_F(RefactoringClientServerInProcess, RequestSourceRangesForQueryMessage)
     RequestSourceRangesForQueryMessage message{
         "functionDecl()",
         {{{TESTDATA_DIR, "query_simplefunction.cpp"},
+          1,
           "void f();",
           {
               "cc",
           },
           1}},
-        {{{TESTDATA_DIR, "query_simplefunction.h"}, "void f();", {}, 1}}};
+        {{{TESTDATA_DIR, "query_simplefunction.h"}, 2, "void f();", {}, 1}}};
 
     EXPECT_CALL(mockRefactoringServer, requestSourceRangesForQueryMessage(message));
 
@@ -182,7 +183,7 @@ TEST_F(RefactoringClientServerInProcess, SendUpdateProjectPartsMessage)
 
 TEST_F(RefactoringClientServerInProcess, SendUpdateGeneratedFilesMessage)
 {
-    FileContainer fileContainer{{"/path/to/", "file"}, "content", {}};
+    FileContainer fileContainer{{"/path/to/", "file"}, 1, "content", {}};
     UpdateGeneratedFilesMessage message{{fileContainer}};
 
     EXPECT_CALL(mockRefactoringServer, updateGeneratedFiles(message));
diff --git a/tests/unit/unittest/refactoringprojectupdater-test.cpp b/tests/unit/unittest/refactoringprojectupdater-test.cpp
index eddeefa24c7..8b16adc6196 100644
--- a/tests/unit/unittest/refactoringprojectupdater-test.cpp
+++ b/tests/unit/unittest/refactoringprojectupdater-test.cpp
@@ -64,6 +64,10 @@ MATCHER_P(IsProjectPartContainer,
 class RefactoringProjectUpdater : public testing::Test
 {
 protected:
+    RefactoringProjectUpdater()
+    {
+        ON_CALL(mockProjectPartsStorage, transactionBackend()).WillByDefault(ReturnRef(database));
+    }
     ProjectPart::Ptr createProjectPart(const char *name)
     {
         ProjectPart::Ptr projectPart{new ProjectPart};
@@ -115,8 +119,6 @@ TEST_F(RefactoringProjectUpdater, UpdateProjectPart)
         .WillRepeatedly(Return(QString(" project1")));
     EXPECT_CALL(mockCppModelManager, projectPartForId(Eq(QString(" project1"))))
         .WillRepeatedly(Return(createProjectPart("project1")));
-    EXPECT_CALL(mockProjectPartsStorage, fetchProjectPartId(Eq(" project1")))
-        .WillOnce(Return(ClangBackEnd::ProjectPartId{3}));
     EXPECT_CALL(mockRefactoringServer,
                 updateProjectParts(Field(&UpdateProjectPartsMessage::projectsParts,
                                          ElementsAre(IsProjectPartContainer(3)))));
diff --git a/tests/unit/unittest/refactoringserver-test.cpp b/tests/unit/unittest/refactoringserver-test.cpp
index 74363de35fc..2cc3f26efd4 100644
--- a/tests/unit/unittest/refactoringserver-test.cpp
+++ b/tests/unit/unittest/refactoringserver-test.cpp
@@ -26,6 +26,7 @@
 #include "googletest.h"
 
 #include "filesystem-utilities.h"
+#include "mockfilepathcaching.h"
 #include "mockrefactoringclient.h"
 #include "mocksymbolindexing.h"
 #include "sourcerangecontainer-matcher.h"
@@ -98,7 +99,11 @@ protected:
     ClangBackEnd::GeneratedFiles generatedFiles;
     ClangBackEnd::RefactoringServer refactoringServer{mockSymbolIndexing, filePathCache, generatedFiles};
     Utils::SmallString sourceContent{"void f()\n {}"};
-    FileContainer source{{TESTDATA_DIR, "query_simplefunction.cpp"}, sourceContent.clone(), {"cc"}};
+    ClangBackEnd::FilePath filePath{TESTDATA_DIR, "query_simplefunction.cpp"};
+    FileContainer source{filePath.clone(),
+                         filePathCache.filePathId(filePath),
+                         sourceContent.clone(),
+                         {"cc"}};
     QTemporaryFile temporaryFile{Utils::TemporaryDirectory::masterDirectoryPath()
                                  + "/clangQuery-XXXXXX.cpp"};
     int processingSlotCount = 2;
@@ -126,9 +131,13 @@ TEST_F(RefactoringServerSlowTest, RequestSingleSourceRangesAndDiagnosticsWithUns
 {
     Utils::SmallString unsavedContent{"void f();"};
     FileContainer source{{TESTDATA_DIR, "query_simplefunction.cpp"},
+                         filePathCache.filePathId(FilePath{TESTDATA_DIR, "query_simplefunction.cpp"}),
                          "#include \"query_simplefunction.h\"",
                          {"cc"}};
-    FileContainer unsaved{{TESTDATA_DIR, "query_simplefunction.h"}, unsavedContent.clone(), {}};
+    FileContainer unsaved{{TESTDATA_DIR, "query_simplefunction.h"},
+                          filePathCache.filePathId(FilePath{TESTDATA_DIR, "query_simplefunction.h"}),
+                          unsavedContent.clone(),
+                          {}};
     RequestSourceRangesForQueryMessage message{"functionDecl()", {source.clone()}, {unsaved.clone()}};
 
     EXPECT_CALL(mockRefactoringClient,
@@ -240,6 +249,8 @@ TEST_F(RefactoringServerSlowTest, ForValidRequestSourceRangesAndDiagnosticsGetSo
 {
     RequestSourceRangesAndDiagnosticsForQueryMessage message("functionDecl()",
                                                              {FilePath(temporaryFile.fileName()),
+                                                              filePathCache.filePathId(FilePath(
+                                                                  temporaryFile.fileName())),
                                                               "void f() {}",
                                                               {"cc"}});
 
@@ -259,6 +270,8 @@ TEST_F(RefactoringServerSlowTest, ForInvalidRequestSourceRangesAndDiagnosticsGet
 {
     RequestSourceRangesAndDiagnosticsForQueryMessage message("func()",
                                                              {FilePath(temporaryFile.fileName()),
+                                                              filePathCache.filePathId(FilePath(
+                                                                  temporaryFile.fileName())),
                                                               "void f() {}",
                                                               {"cc"}});
 
@@ -277,6 +290,7 @@ TEST_F(RefactoringServerSlowTest, ForInvalidRequestSourceRangesAndDiagnosticsGet
 TEST_F(RefactoringServer, UpdateGeneratedFilesSetMemberWhichIsUsedForSymbolIndexing)
 {
     FileContainers unsaved{{{TESTDATA_DIR, "query_simplefunction.h"},
+                            filePathCache.filePathId(FilePath{TESTDATA_DIR, "query_simplefunction.h"}),
                             "void f();",
                             {}}};
 
@@ -288,6 +302,7 @@ TEST_F(RefactoringServer, UpdateGeneratedFilesSetMemberWhichIsUsedForSymbolIndex
 TEST_F(RefactoringServer, RemoveGeneratedFilesSetMemberWhichIsUsedForSymbolIndexing)
 {
     FileContainers unsaved{{{TESTDATA_DIR, "query_simplefunction.h"},
+                            filePathCache.filePathId(FilePath{TESTDATA_DIR, "query_simplefunction.h"}),
                             "void f();",
                             {}}};
     refactoringServer.updateGeneratedFiles(Utils::clone(unsaved));
@@ -297,8 +312,12 @@ TEST_F(RefactoringServer, RemoveGeneratedFilesSetMemberWhichIsUsedForSymbolIndex
     ASSERT_THAT(generatedFiles.fileContainers(), IsEmpty());
 }
 
-TEST_F(RefactoringServer, UpdateProjectPartsCallsSymbolIndexingUpdateProjectParts)
+TEST_F(RefactoringServer, UpdateProjectPartsCalls)
 {
+    NiceMock<MockFilePathCaching> mockFilePathCaching;
+    ClangBackEnd::RefactoringServer refactoringServer{mockSymbolIndexing,
+                                                      mockFilePathCaching,
+                                                      generatedFiles};
     ProjectPartContainers projectParts{
         {{1,
           {"-I", TESTDATA_DIR},
@@ -313,8 +332,8 @@ TEST_F(RefactoringServer, UpdateProjectPartsCallsSymbolIndexingUpdateProjectPart
           Utils::LanguageVersion::C11,
           Utils::LanguageExtension::All}}};
 
-    EXPECT_CALL(mockSymbolIndexing,
-                updateProjectParts(projectParts));
+    EXPECT_CALL(mockFilePathCaching, populateIfEmpty());
+    EXPECT_CALL(mockSymbolIndexing, updateProjectParts(projectParts));
 
     refactoringServer.updateProjectParts({Utils::clone(projectParts), {}});
 }
diff --git a/tests/unit/unittest/symbolindexer-test.cpp b/tests/unit/unittest/symbolindexer-test.cpp
index 127921ca985..25c7056f022 100644
--- a/tests/unit/unittest/symbolindexer-test.cpp
+++ b/tests/unit/unittest/symbolindexer-test.cpp
@@ -203,6 +203,7 @@ protected:
                                       Utils::LanguageVersion::CXX14,
                                       Utils::LanguageExtension::None};
     FileContainers unsaved{{{TESTDATA_DIR, "query_simplefunction.h"},
+                            filePathId(TESTDATA_DIR "/query_simplefunction.h"),
                             "void f();",
                             {}}};
     SymbolEntries symbolEntries{{1, {"function", "function", SymbolKind::Function}}};
diff --git a/tests/unit/unittest/symbolscollector-test.cpp b/tests/unit/unittest/symbolscollector-test.cpp
index cdefde2a31b..675a4af6d47 100644
--- a/tests/unit/unittest/symbolscollector-test.cpp
+++ b/tests/unit/unittest/symbolscollector-test.cpp
@@ -264,8 +264,10 @@ TEST_F(SymbolsCollector, ReferencedSymboldMatchesLocation)
 
 TEST_F(SymbolsCollector, DISABLED_ON_WINDOWS(CollectInUnsavedFile))
 {
-    FileContainers unsaved{
-        {{TESTDATA_DIR, "symbolscollector/generated_file.h"}, "void function();", {}}};
+    FileContainers unsaved{{{TESTDATA_DIR, "symbolscollector/generated_file.h"},
+                            filePathId({TESTDATA_DIR, "symbolscollector/generated_file.h"}),
+                            "void function();",
+                            {}}};
     collector.setFile(filePathId(TESTDATA_DIR "/symbolscollector/unsaved.cpp"), {"cc"});
     collector.setUnsavedFiles(std::move(unsaved));