From 46ca72323018c9e31878bc7629e303fc6c05d073 Mon Sep 17 00:00:00 2001
From: Arttu Tarkiainen <arttu.tarkiainen@qt.io>
Date: Wed, 8 Feb 2023 15:53:06 +0200
Subject: Metadata cache: register items by renaming instead of copying

This is much more efficient than recursively copying the contents of
each downloaded repository entry. Testing on a Linux debug build with
a large amount of components, a rough estimate of the time reduction
for performing update of an almost empty cache was over 60 percent.

Task-number: QTIFW-2971
Change-Id: I866514af092f9c4b5e322562d6f972c57c8c03f5
Reviewed-by: Katja Marttila <katja.marttila@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
---
 src/libs/installer/genericdatacache.cpp | 38 ++++++++++++++++++++++++++++-----
 src/libs/installer/genericdatacache.h   |  7 +++++-
 src/libs/installer/metadatajob_p.h      |  2 +-
 3 files changed, 40 insertions(+), 7 deletions(-)

(limited to 'src')

diff --git a/src/libs/installer/genericdatacache.cpp b/src/libs/installer/genericdatacache.cpp
index fd264ce63..d8db99600 100644
--- a/src/libs/installer/genericdatacache.cpp
+++ b/src/libs/installer/genericdatacache.cpp
@@ -119,6 +119,16 @@ CacheableItem::~CacheableItem()
     calling \l{sync()}.
 */
 
+/*!
+    \enum GenericDataCache::RegisterMode
+    This enum holds the possible values for modes of registering items to cache.
+
+    \value Copy
+           The contents of the item are copied to the cache.
+    \value Move
+           The contents of the item are move to the cache.
+*/
+
 /*!
     \fn template <typename T> QInstaller::GenericDataCache<T>::GenericDataCache()
 
@@ -417,13 +427,14 @@ T *GenericDataCache<T>::itemByPath(const QString &path) const
     the new \a item replaces a previous item with the same checksum.
 
     The cache takes ownership of the object pointed by \a item. The contents of the
-    item are copied to the cache with a subdirectory name that matches the checksum
-    of the item.
+    item are copied or moved to the cache with a subdirectory name that matches the checksum
+    of the item. The \c mode decides how the contents of the item are registered, either by
+    copying or moving.
 
     Returns \c true on success or \c false if the item could not be registered.
 */
 template <typename T>
-bool GenericDataCache<T>::registerItem(T *item, bool replace)
+bool GenericDataCache<T>::registerItem(T *item, bool replace, RegisterMode mode)
 {
     QMutexLocker _(&m_mutex);
     if (m_invalidated) {
@@ -455,10 +466,27 @@ bool GenericDataCache<T>::registerItem(T *item, bool replace)
     const QString newPath = m_path + QDir::separator() + QString::fromLatin1(item->checksum());
     try {
         // A directory is in the way but it isn't registered to the current cache, remove.
-        if (QDir().exists(newPath))
+        QDir dir;
+        if (dir.exists(newPath))
             QInstaller::removeDirectory(newPath);
 
-        QInstaller::copyDirectoryContents(item->path(), newPath);
+        switch (mode) {
+        case Copy:
+            QInstaller::copyDirectoryContents(item->path(), newPath);
+            break;
+        case Move:
+            // First, try moving the top level directory
+            if (!dir.rename(item->path(), newPath)) {
+                qCDebug(lcDeveloperBuild) << "Failed to rename directory" << item->path()
+                    << "to" << newPath << ". Trying again.";
+                // If that does not work, fallback to moving the contents one by one
+                QInstaller::moveDirectoryContents(item->path(), newPath);
+            }
+            break;
+        default:
+            throw Error(QCoreApplication::translate("GenericDataCache",
+                "Unknown register mode selected!"));
+        }
     } catch (const Error &e) {
         setErrorString(QCoreApplication::translate("GenericDataCache",
             "Error while copying item to path \"%1\": %2").arg(newPath, e.message()));
diff --git a/src/libs/installer/genericdatacache.h b/src/libs/installer/genericdatacache.h
index 2bdf6697e..5c1732334 100644
--- a/src/libs/installer/genericdatacache.h
+++ b/src/libs/installer/genericdatacache.h
@@ -64,6 +64,11 @@ template <typename T>
 class INSTALLER_EXPORT GenericDataCache
 {
 public:
+    enum RegisterMode {
+        Copy = 0,
+        Move = 1
+    };
+
     GenericDataCache();
     explicit GenericDataCache(const QString &path, const QString &type, const QString &version);
     ~GenericDataCache();
@@ -85,7 +90,7 @@ public:
     T *itemByChecksum(const QByteArray &checksum) const;
     T *itemByPath(const QString &path) const;
 
-    bool registerItem(T *item, bool replace = false);
+    bool registerItem(T *item, bool replace = false, RegisterMode mode = Copy);
     bool removeItem(const QByteArray &checksum);
 
     QList<T *> obsoleteItems() const;
diff --git a/src/libs/installer/metadatajob_p.h b/src/libs/installer/metadatajob_p.h
index ef2729dbb..5340e5d1c 100644
--- a/src/libs/installer/metadatajob_p.h
+++ b/src/libs/installer/metadatajob_p.h
@@ -140,7 +140,7 @@ public:
         QStringList registeredKeys;
         bool success = true;
         for (auto *meta : qAsConst(*m_updates)) {
-            if (!m_cache->registerItem(meta, true)) {
+            if (!m_cache->registerItem(meta, true, GenericDataCache<Metadata>::Move)) {
                 success = false;
                 break;
             }
-- 
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