[3.8] Speed up process template page

Kitodo-DataManagement/src/main/java/org/kitodo/data/database/persistence/BaseDAO.java

@@ -259,6 +259,22 @@ public Long count(String query) throws DAOException {
         }
     }
 
+    /**
+     * Executes an HQL query that returns scalar projections (e.g., specific fields or aggregate results)
+     * instead of full entity objects.
+     *
+     * @param hql the HQL query string
+     * @param parameters query parameters
+     * @return list of scalar projection results
+     */
+    public List<Object[]> getProjectionByQuery(String hql, Map<String, Object> parameters) {
+        try (Session session = HibernateUtil.getSession()) {
+            Query<Object[]> query = session.createQuery(hql, Object[].class);
+            addParameters(query, parameters);
+            return query.getResultList();
+        }
+    }
+
     /**
      * Removes the object from the database with with specified class type and
      * {@code id}.

Kitodo/src/main/java/org/kitodo/production/forms/TemplateForm.java

@@ -17,10 +17,11 @@
 import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 
 import javax.annotation.PostConstruct;
-import javax.enterprise.context.SessionScoped;
+import javax.faces.view.ViewScoped;
 import javax.inject.Named;
 
 import org.apache.commons.lang3.StringUtils;
@@ -46,7 +47,7 @@
 import org.kitodo.production.workflow.model.Converter;
 
 @Named("TemplateForm")
-@SessionScoped
+@ViewScoped
 public class TemplateForm extends TemplateBaseForm {
 
     private static final Logger logger = LogManager.getLogger(TemplateForm.class);
@@ -60,6 +61,7 @@ public class TemplateForm extends TemplateBaseForm {
     private List<String> templateFilters;
     private List<String> selectedTemplateFilters;
     private static final String DEACTIVATED_TEMPLATES_FILTER = "deactivatedTemplates";
+    private Map<Integer,Boolean> templateUsageMap;
 
     /**
      * Constructor.
@@ -458,12 +460,11 @@ private void prepareTasks() throws DAOException, IOException, WorkflowException,
      * @return whether template is used by any processes or not
      */
     public boolean isTemplateUsed(int templateId) {
-        try {
-            return !ServiceManager.getProcessService().findByTemplate(templateId).isEmpty();
-        } catch (DataException e) {
-            Helper.setErrorMessage(e);
-            return false;
+        if (Objects.isNull(templateUsageMap)) {
+            templateUsageMap = ServiceManager.getTemplateService().getTemplateUsageMap();
         }
+        Boolean isUsed = templateUsageMap.get(templateId);
+        return Boolean.TRUE.equals(isUsed);
     }
 
     /**

Kitodo/src/main/java/org/kitodo/production/services/data/TemplateService.java

@@ -86,6 +86,27 @@ public static TemplateService getInstance() {
         return localReference;
     }
 
+    /**
+     * Retrieves a map indicating the usage status of templates.
+     * The method executes an HQL query to determine whether each template is used
+     * (i.e., has associated processes).
+     *
+     * @return a map where the key is the template ID and the value is a boolean
+     *         indicating whether the template is used
+     */
+    public Map<Integer, Boolean> getTemplateUsageMap() {
+        String hql = "SELECT t.id AS templateId, "
+                + " CASE WHEN EXISTS (SELECT 1 FROM Process p WHERE p.template.id = t.id) "
+                + " THEN true ELSE false END AS isUsed "
+                + " FROM Template t";
+        List<Object[]> results = getProjectionByQuery(hql);
+        return results.stream()
+                .collect(Collectors.toMap(
+                        row -> (Integer) row[0], // templateId
+                        row -> (Boolean) row[1]  // isUsed
+                ));
+    }
+
     @Override
     public Long countDatabaseRows() throws DAOException {
         return countDatabaseRows("SELECT COUNT(*) FROM Template");

Kitodo/src/main/java/org/kitodo/production/services/data/base/SearchDatabaseService.java

@@ -197,6 +197,17 @@ public List<T> getAll(int offset, int size) throws DAOException {
         return dao.getAll(offset, size);
     }
 
+    /**
+     * Executes an HQL query that returns scalar projections (e.g., specific fields or aggregate results)
+     * instead of full entity objects.
+     *
+     * @param hql the HQL query string
+     * @return list of scalar projection results
+     */
+    protected List<Object[]> getProjectionByQuery(String hql) {
+        return dao.getProjectionByQuery(hql, null);
+    }
+
     /**
      * Evict given bean object.
      *

Kitodo/src/test/java/org/kitodo/production/services/data/TemplateServiceIT.java

@@ -18,6 +18,7 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.List;
+import java.util.Map;
 
 import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.BeforeAll;
@@ -102,4 +103,17 @@ public void shouldHasCompleteTasks() throws Exception {
         condition = templateService.hasCompleteTasks(templateDTO.getTasks());
         assertFalse(condition, "Process DTO has complete tasks!");
     }
+
+    @Test
+    public void shouldCorrectlyDetermineTemplateUsage() throws Exception {
+        Map<Integer, Boolean> templateUsageMap = templateService.getTemplateUsageMap();
+        Map<Integer, Boolean> expectedMap = Map.of(
+                1, true,
+                2, false,
+                3, false,
+                4, false
+        );
+        // Assert that the generated map matches the expected map
+        assertEquals(expectedMap, templateUsageMap, "The template usage map does not match expected results.");
+    }
 }