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, 1 insertions, 2 deletions

diff --git a/src/libs/installer/installercalculator.h b/src/libs/installer/installercalculator.h
index d952a1e8c..c2fa8761c 100644
--- a/src/libs/installer/installercalculator.h
+++ b/src/libs/installer/installercalculator.h
@@ -43,7 +43,7 @@ class Component;
 class INSTALLER_EXPORT InstallerCalculator
 {
 public:
-    InstallerCalculator(PackageManagerCore *core, const QList<Component *> &allComponents, const AutoDependencyHash &autoDependencyComponentHash);
+    InstallerCalculator(PackageManagerCore *core, const AutoDependencyHash &autoDependencyComponentHash);
 
     enum InstallReasonType
     {
@@ -75,7 +75,6 @@ private:
 
 private:
     PackageManagerCore *m_core;
-    QList<Component*> m_allComponents;
     QHash<Component*, QSet<Component*> > m_visitedComponents;
     QList<const Component*> m_componentsForAutodepencencyCheck;
     //for faster lookups.