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.

2 files changed, 52 insertions, 2 deletions

diff --git a/server/src/com/vaadin/data/util/AbstractInMemoryContainer.java b/server/src/com/vaadin/data/util/AbstractInMemoryContainer.java
index 6eea9cb421..dbfcad3982 100644
--- a/server/src/com/vaadin/data/util/AbstractInMemoryContainer.java
+++ b/server/src/com/vaadin/data/util/AbstractInMemoryContainer.java
@@ -26,6 +26,7 @@ import java.util.Set;
 import com.vaadin.data.Container;
 import com.vaadin.data.Container.ItemSetChangeNotifier;
 import com.vaadin.data.Item;
+import com.vaadin.data.RangeOutOfContainerBoundsException;
 import com.vaadin.data.util.filter.SimpleStringFilter;
 import com.vaadin.data.util.filter.UnsupportedFilterException;
 
@@ -251,6 +252,45 @@ public abstract class AbstractInMemoryContainer<ITEMIDTYPE, PROPERTYIDCLASS, ITE
     }
 
     @Override
+    public List<ITEMIDTYPE> getItemIds(int startIndex, int numberOfIds) {
+        if (startIndex < 0) {
+            throw new IndexOutOfBoundsException(
+                    "Start index cannot be negative! startIndex=" + startIndex);
+        }
+
+        if (startIndex > getVisibleItemIds().size()) {
+            throw new IndexOutOfBoundsException(
+                    "Start index exceeds container size! startIndex="
+                            + startIndex + " containerLastItemIndex="
+                            + (getVisibleItemIds().size() - 1));
+        }
+
+        if (numberOfIds < 1) {
+            if (numberOfIds == 0) {
+                return Collections.emptyList();
+            }
+
+            throw new IllegalArgumentException(
+                    "Cannot get negative amount of items! numberOfItems="
+                            + numberOfIds);
+        }
+
+        int endIndex = startIndex + numberOfIds;
+
+        if (endIndex > getVisibleItemIds().size()) {
+            throw new RangeOutOfContainerBoundsException(
+                    "Cannot get all requested item ids from container. "
+                            + "Container size might have changed, recalculate numberOfIds "
+                            + "based on the actual container size!",
+                    startIndex, numberOfIds, getVisibleItemIds().size());
+        }
+
+        return Collections.unmodifiableList(getVisibleItemIds().subList(
+                startIndex, endIndex));
+
+    }
+
+    @Override
     public int indexOfId(Object itemId) {
         return getVisibleItemIds().indexOf(itemId);
     }
diff --git a/server/src/com/vaadin/data/util/sqlcontainer/SQLContainer.java b/server/src/com/vaadin/data/util/sqlcontainer/SQLContainer.java
index a53f32b96e..7a63e8c6c2 100644
--- a/server/src/com/vaadin/data/util/sqlcontainer/SQLContainer.java
+++ b/server/src/com/vaadin/data/util/sqlcontainer/SQLContainer.java
@@ -33,6 +33,7 @@ import java.util.logging.Level;
 import java.util.logging.Logger;
 
 import com.vaadin.data.Container;
+import com.vaadin.data.ContainerHelpers;
 import com.vaadin.data.Item;
 import com.vaadin.data.Property;
 import com.vaadin.data.util.filter.Compare.Equal;
@@ -656,9 +657,11 @@ public class SQLContainer implements Container, Container.Filterable,
 
     @Override
     public Object getIdByIndex(int index) {
-        if (index < 0 || index > size() - 1) {
-            return null;
+        if (index < 0) {
+            throw new IndexOutOfBoundsException("Index is negative! index="
+                    + index);
         }
+
         if (index < size) {
             if (itemIndexes.keySet().contains(index)) {
                 return itemIndexes.get(index);
@@ -672,6 +675,13 @@ public class SQLContainer implements Container, Container.Filterable,
         }
     }
 
+    @Override
+    public List<Object> getItemIds(int startIndex, int numberOfIds) {
+        // TODO create a better implementation
+        return (List<Object>) ContainerHelpers.getItemIdsUsingGetIdByIndex(
+                startIndex, numberOfIds, this);
+    }
+
     /**********************************************/
     /** Methods from interface Container.Ordered **/
     /**********************************************/