Optimize retrieving components by name

The PackageManagerCore::componentByName(const QString &name)
-function is called repeatedly by the InstallerCalculator class
and at minimum once for each install script, because we
automatically inject a snippet which stores the return value
of the function in the 'component' variable for the script context.

Create a <name, component> hash once per each component model reset
to make the lookups faster:

* This avoids constructing a flat list of components and all
  their descendants again and again when calling the function.

* The linear lookup from the component list is slow because it
  calls componentMatches() for each element until the satisfactory
  component was found or the list ends.

* The average time complexity of the key lookup from the QHash
  is constant even for large hashes.

Task-number: QTIFW-2790
Change-Id: I580d28f78ac6681d5bcbfbad970002b49de1a830
Reviewed-by: Katja Marttila <katja.marttila@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/libs/installer/packagemanagercore_p.cpp b/src/libs/installer/packagemanagercore_p.cpp
index eddb44555..f4d47b718 100644
--- a/src/libs/installer/packagemanagercore_p.cpp
+++ b/src/libs/installer/packagemanagercore_p.cpp
@@ -459,6 +459,7 @@ void PackageManagerCorePrivate::cleanUpComponentEnvironment()
     m_autoDependencyComponentHash.clear();
     m_localDependencyComponentHash.clear();
     m_localVirtualComponents.clear();
+    m_componentByNameHash.clear();
     // clean up registered (downloaded) data
     if (m_core->isMaintainer())
         BinaryFormatEngineHandler::instance()->clear();
@@ -564,8 +565,7 @@ InstallerCalculator *PackageManagerCorePrivate::installerCalculator() const
 {
     if (!m_installerCalculator) {
         PackageManagerCorePrivate *const pmcp = const_cast<PackageManagerCorePrivate *> (this);
-        pmcp->m_installerCalculator = new InstallerCalculator(m_core,
-            m_core->components(PackageManagerCore::ComponentType::AllNoReplacements), pmcp->m_autoDependencyComponentHash);
+        pmcp->m_installerCalculator = new InstallerCalculator(m_core, pmcp->m_autoDependencyComponentHash);
     }
     return m_installerCalculator;
 }