Reduce freeze times on updating search results on resource changes

If the search view shows ~100000 matches, deleting resources that are
shown in the search view freezes Eclipse for many minutes. With this
change the freeze is only about 30 seconds.

See #2279

bundles/org.eclipse.search/META-INF/MANIFEST.MF

@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %pluginName
 Bundle-SymbolicName: org.eclipse.search; singleton:=true
-Bundle-Version: 3.16.300.qualifier
+Bundle-Version: 3.17.0.qualifier
 Bundle-Activator: org.eclipse.search.internal.ui.SearchPlugin
 Bundle-ActivationPolicy: lazy
 Bundle-Vendor: %providerName

bundles/org.eclipse.search/newsearch/org/eclipse/search/ui/text/AbstractTextSearchResult.java

@@ -21,6 +21,7 @@
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map.Entry;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
@@ -308,6 +309,19 @@ public int getMatchCount() {
 		return count;
 	}
 
+	/**
+	 * @return {@code true} if the result is not empty
+	 * @since 3.17
+	 */
+	public boolean hasMatches() {
+		for (Entry<Object, Set<Match>> entry : fElementsToMatches.entrySet()) {
+			if (!entry.getValue().isEmpty()) {
+				return true;
+			}
+		}
+		return false;
+	}
+
 	/**
 	 * Returns the number of matches reported against a given element. This is
 	 * equivalent to calling <code>getMatches(element).length</code>

bundles/org.eclipse.search/search/org/eclipse/search/internal/ui/text/FileTreeContentProvider.java

@@ -32,9 +32,11 @@
 
 import org.eclipse.core.resources.IProject;
 import org.eclipse.core.resources.IResource;
+
 import org.eclipse.jface.viewers.AbstractTreeViewer;
 import org.eclipse.jface.viewers.ITreeContentProvider;
 import org.eclipse.jface.viewers.Viewer;
+
 import org.eclipse.search.ui.text.AbstractTextSearchResult;
 import org.eclipse.search.ui.text.Match;
 import org.eclipse.search.ui.text.MatchFilter;
@@ -177,17 +179,27 @@ private boolean hasMatches(Object element) {
 		if (element instanceof LineElement) {
 			LineElement lineElement= (LineElement) element;
 			IResource resource = lineElement.getParent();
-			if (getMatchCount(resource) > 0) {
+			if (hasMatches(resource)) {
 				return lineElement.hasMatches(fResult);
 			}
 		}
 		return fPage.getDisplayedMatchCount(element) > 0;
 	}
 
+	private boolean hasMatches(IResource element) {
+		if (hasActiveMatchFilters()) {
+			return fPage.getDisplayedMatchCount(element) > 0;
+		} else {
+			return fResult.hasMatches();
+		}
+	}
+
 	private int getMatchCount(Object element) {
-		return fResult.getActiveMatchFilters() != null && fResult.getActiveMatchFilters().length > 0
-				? fPage.getDisplayedMatchCount(element)
-				: fResult.getMatchCount();
+		if (hasActiveMatchFilters()) {
+			return fPage.getDisplayedMatchCount(element);
+		} else {
+			return fResult.getMatchCount();
+		}
 	}
 
 	private void removeFromSiblings(Object element, Object parent) {
@@ -207,7 +219,11 @@ public Object[] getChildren(Object parentElement) {
 
 	@Override
 	public boolean hasChildren(Object element) {
-		return getChildren(element).length > 0;
+		Set<Object> children = fChildrenMap.get(element);
+		if (children == null) {
+			return false;
+		}
+		return !children.isEmpty();
 	}
 
 	static <T> Stream<T> toStream(Enumeration<T> e) {
@@ -243,7 +259,7 @@ public synchronized void elementsChanged(Object[] updatedElements) {
 		Set<LineElement> lineMatches = Collections.emptySet();
 		// if we have active match filters, we should only use non-filtered FileMatch
 		// objects to collect LineElements to update
-		if (fResult.getActiveMatchFilters() != null && fResult.getActiveMatchFilters().length > 0) {
+		if (hasActiveMatchFilters()) {
 			lineMatches = Arrays.stream(updatedElements).filter(LineElement.class::isInstance)
 				// only for distinct files:
 				.map(u -> ((LineElement) u).getParent()).distinct()
@@ -292,6 +308,11 @@ public synchronized void elementsChanged(Object[] updatedElements) {
 		}
 	}
 
+	private boolean hasActiveMatchFilters() {
+		MatchFilter[] activeMatchFilters = fResult.getActiveMatchFilters();
+		return activeMatchFilters != null && activeMatchFilters.length > 0;
+	}
+
 	@Override
 	public void clear() {
 		initialize(fResult);