Do not evaluate unneeded rows when quick offset is used

h2/src/main/org/h2/command/dml/Select.java

@@ -706,8 +706,7 @@ public class Select extends Query {
         }
         ArrayList<Row>[] forUpdateRows = initForUpdateRows();
         int sampleSize = getSampleSizeValue(session);
-        LazyResultQueryFlat lazyResult = new LazyResultQueryFlat(expressionArray,
-                sampleSize, columnCount);
+        LazyResultQueryFlat lazyResult = new LazyResultQueryFlat(expressionArray, sampleSize, columnCount);
         skipOffset(lazyResult, offset, quickOffset);
         if (result == null) {
             return lazyResult;
@@ -770,7 +769,7 @@ public class Select extends Query {
 
     private static void skipOffset(LazyResultSelect lazyResult, long offset, boolean quickOffset) {
         if (quickOffset) {
-            while (offset > 0 && lazyResult.next()) {
+            while (offset > 0 && lazyResult.skip()) {
                 offset--;
             }
         }
@@ -1883,8 +1882,7 @@ public class Select extends Query {
 
         @Override
         protected Value[] fetchNextRow() {
-            while ((sampleSize <= 0 || rowNumber < sampleSize) &&
-                    topTableFilter.next()) {
+            while ((sampleSize <= 0 || rowNumber < sampleSize) && topTableFilter.next()) {
                 setCurrentRowNumber(rowNumber + 1);
                 if (isConditionMet()) {
                     ++rowNumber;
@@ -1898,6 +1896,18 @@ public class Select extends Query {
             }
             return null;
         }
+
+        @Override
+        protected boolean skipNextRow() {
+            while ((sampleSize <= 0 || rowNumber < sampleSize) && topTableFilter.next()) {
+                setCurrentRowNumber(rowNumber + 1);
+                if (isConditionMet()) {
+                    ++rowNumber;
+                    return true;
+                }
+            }
+            return false;
+        }
     }
 
     /**

h2/src/main/org/h2/result/LazyResult.java

@@ -71,6 +71,27 @@ public abstract class LazyResult implements ResultInterface {
         return false;
     }
 
+    /**
+     * Go to the next row and skip it.
+     *
+     * @return true if a row exists
+     */
+    public boolean skip() {
+        if (closed || afterLast) {
+            return false;
+        }
+        currentRow = null;
+        if (nextRow != null) {
+            nextRow = null;
+            return true;
+        }
+        if (skipNextRow()) {
+            return true;
+        }
+        afterLast = true;
+        return false;
+    }
+
     @Override
     public boolean hasNext() {
         if (closed || afterLast) {
@@ -89,6 +110,15 @@ public abstract class LazyResult implements ResultInterface {
      */
     protected abstract Value[] fetchNextRow();
 
+    /**
+     * Skip next row.
+     *
+     * @return true if next row was available
+     */
+    protected boolean skipNextRow() {
+        return fetchNextRow() != null;
+    }
+
     @Override
     public boolean isAfterLast() {
         return afterLast;