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, 3 deletions

diff --git a/tests/auto/installer/solver/tst_solver.cpp b/tests/auto/installer/solver/tst_solver.cpp
index 8b5d1fdcf..bdfc4d3df 100644
--- a/tests/auto/installer/solver/tst_solver.cpp
+++ b/tests/auto/installer/solver/tst_solver.cpp
@@ -192,8 +192,7 @@ private slots:
         QFETCH(QList<int>, installReason);
         QFETCH(AutoDependencyHash, autodependencyHash);
 
-        InstallerCalculator calc(core, core->components(PackageManagerCore::ComponentType::AllNoReplacements)
-                                 , autodependencyHash);
+        InstallerCalculator calc(core, autodependencyHash);
         calc.appendComponentsToInstall(selectedComponents);
         QList<Component *> result = calc.orderedComponentsToInstall();
 
@@ -236,7 +235,7 @@ private slots:
         QFETCH(QList<Component *> , selectedComponents);
         QFETCH(QList<Component *> , expectedResult);
 
-        InstallerCalculator calc(core, core->components(PackageManagerCore::ComponentType::AllNoReplacements), QHash<QString, QStringList>());
+        InstallerCalculator calc(core, QHash<QString, QStringList>());
         QTest::ignoreMessage(QtWarningMsg, "Cannot find missing dependency \"B->=2.0.0\" for \"A\".");
         calc.appendComponentsToInstall(selectedComponents);