Add Index.isFindSlow() and use it in IndexCursor to prevent multiple table scans in FunctionIndex

h2/src/main/org/h2/index/BaseIndex.java

@@ -120,6 +120,10 @@ public abstract class BaseIndex extends SchemaObjectBase implements Index {
         return false;
     }
 
+    @Override
+    public boolean isFindSlow() {
+        return false;
+    }
 
     @Override
     public Cursor find(TableFilter filter, SearchRow first, SearchRow last) {

h2/src/main/org/h2/index/FunctionIndex.java

@@ -44,6 +44,11 @@ public class FunctionIndex extends BaseIndex {
         throw DbException.getUnsupportedException("ALIAS");
     }
 
+    @Override
+    public boolean isFindSlow() {
+        return true;
+    }
+
     @Override
     public Cursor find(Session session, SearchRow first, SearchRow last) {
         if (functionTable.isBufferResultSetToLocalTemp()) {

h2/src/main/org/h2/index/Index.java

@@ -51,6 +51,15 @@ public interface Index extends SchemaObject {
      */
     void remove(Session session, Row row);
 
+    /**
+     * Returns {@code true} if {@code find()} implementation performs scan over all
+     * index, {@code false} if {@code find()} performs the fast lookup.
+     *
+     * @return {@code true} if {@code find()} implementation performs scan over all
+     *         index, {@code false} if {@code find()} performs the fast lookup
+     */
+    boolean isFindSlow();
+
     /**
      * Find a row or a list of rows and create a cursor to iterate over the
      * result.

h2/src/main/org/h2/index/IndexCursor.java

@@ -89,6 +89,9 @@ public class IndexCursor implements Cursor {
                 alwaysFalse = true;
                 break;
             }
+            if (index.isFindSlow()) {
+                continue;
+            }
             Column column = condition.getColumn();
             if (condition.getCompareType() == Comparison.IN_LIST) {
                 if (start == null && end == null) {

h2/src/main/org/h2/index/MultiVersionIndex.java

@@ -72,6 +72,11 @@ public class MultiVersionIndex implements Index {
         }
     }
 
+    @Override
+    public boolean isFindSlow() {
+        return base.isFindSlow();
+    }
+
     @Override
     public Cursor find(TableFilter filter, SearchRow first, SearchRow last) {
         synchronized (sync) {