Add Container.Indexed.getItemIds(int, int) for a range of items (#8028)

This permits optimization of data fetches from various containers
where getting single items by index in a loop might be costly.

Also add a helper method in ContainerHelpers to make it easier to
implement the new method where performance of fetching an id by index is
not an issue. SQLContainer still uses this helper instead of an
optimized implementation.

1 files changed, 34 insertions, 28 deletions

diff --git a/server/src/com/vaadin/ui/ComboBox.java b/server/src/com/vaadin/ui/ComboBox.java
index da3d2fd91d..2555aac339 100644
--- a/server/src/com/vaadin/ui/ComboBox.java
+++ b/server/src/com/vaadin/ui/ComboBox.java
@@ -358,39 +358,45 @@ public class ComboBox extends AbstractSelect implements
             filterable.addContainerFilter(filter);
         }
 
-        Indexed indexed = (Indexed) container;
+        // try-finally to ensure that the filter is removed from container even
+        // if a exception is thrown...
+        try {
+            Indexed indexed = (Indexed) container;
 
-        int indexToEnsureInView = -1;
+            int indexToEnsureInView = -1;
 
-        // if not an option request (item list when user changes page), go
-        // to page with the selected item after filtering if accepted by
-        // filter
-        Object selection = getValue();
-        if (isScrollToSelectedItem() && !optionRequest && selection != null) {
-            // ensure proper page
-            indexToEnsureInView = indexed.indexOfId(selection);
-        }
+            // if not an option request (item list when user changes page), go
+            // to page with the selected item after filtering if accepted by
+            // filter
+            Object selection = getValue();
+            if (isScrollToSelectedItem() && !optionRequest && selection != null) {
+                // ensure proper page
+                indexToEnsureInView = indexed.indexOfId(selection);
+            }
 
-        filteredSize = container.size();
-        currentPage = adjustCurrentPage(currentPage, needNullSelectOption,
-                indexToEnsureInView, filteredSize);
-        int first = getFirstItemIndexOnCurrentPage(needNullSelectOption,
-                filteredSize);
-        int last = getLastItemIndexOnCurrentPage(needNullSelectOption,
-                filteredSize, first);
-
-        List<Object> options = new ArrayList<Object>();
-        for (int i = first; i <= last && i < filteredSize; ++i) {
-            options.add(indexed.getIdByIndex(i));
-        }
+            filteredSize = container.size();
+            currentPage = adjustCurrentPage(currentPage, needNullSelectOption,
+                    indexToEnsureInView, filteredSize);
+            int first = getFirstItemIndexOnCurrentPage(needNullSelectOption,
+                    filteredSize);
+            int last = getLastItemIndexOnCurrentPage(needNullSelectOption,
+                    filteredSize, first);
 
-        // to the outside, filtering should not be visible
-        if (filter != null) {
-            filterable.removeContainerFilter(filter);
-            filteringContainer = false;
-        }
+            // Compute the number of items to fetch from the indexes given or
+            // based on the filtered size of the container
+            int lastItemToFetch = Math.min(last, filteredSize - 1);
+            int nrOfItemsToFetch = (lastItemToFetch + 1) - first;
+
+            List<?> options = indexed.getItemIds(first, nrOfItemsToFetch);
 
-        return options;
+            return options;
+        } finally {
+            // to the outside, filtering should not be visible
+            if (filter != null) {
+                filterable.removeContainerFilter(filter);
+                filteringContainer = false;
+            }
+        }
     }
 
     /**