Transaction OperationCursor now implements a skip method.

arangod/Indexes/IndexIterator.cpp

@@ -103,11 +103,12 @@ void IndexIterator::reset() {}
 /// @brief default implementation for skip
 ////////////////////////////////////////////////////////////////////////////////
 
-void IndexIterator::skip(uint64_t count) {
+void IndexIterator::skip(uint64_t count, uint64_t& skipped) {
   // Skip the first count-many entries
   // TODO: Can be improved
   while (count > 0 && next() != nullptr) {
     --count;
+    skipped++;
   }
 }
 

arangod/Indexes/IndexIterator.h

@@ -71,7 +71,7 @@ class IndexIterator {
 
   virtual void reset();
 
-  virtual void skip(uint64_t count);
+  virtual void skip(uint64_t count, uint64_t& skipped);
 };
 
 ////////////////////////////////////////////////////////////////////////////////

arangod/Utils/OperationCursor.cpp

@@ -64,3 +64,32 @@ int OperationCursor::getMore(uint64_t batchSize) {
   }
   return TRI_ERROR_NO_ERROR;
 }
+
+//////////////////////////////////////////////////////////////////////////////
+/// @brief Skip the next toSkip many elements.
+///        skipped will be increased by the amount of skipped elements afterwards
+///        Check hasMore()==true before using this
+///        NOTE: This will throw on OUT_OF_MEMORY
+//////////////////////////////////////////////////////////////////////////////
+
+int OperationCursor::skip(uint64_t toSkip, uint64_t& skipped) {
+  if (!hasMore()) {
+    TRI_ASSERT(false);
+    // You requested more even if you should have checked it before.
+    return TRI_ERROR_FORBIDDEN;
+  }
+
+  if (toSkip > _limit) {
+    // Short-cut, we jump to the end
+    _limit = 0;
+    _hasMore = false;
+    return TRI_ERROR_NO_ERROR;
+  }
+
+  _indexIterator->skip(toSkip, skipped);
+  _limit -= skipped;
+  if (skipped != toSkip || _limit == 0) {
+    _hasMore = false;
+  }
+  return TRI_ERROR_NO_ERROR;
+}

arangod/Utils/OperationCursor.h

@@ -100,7 +100,7 @@ struct OperationCursor : public OperationResult {
 ///        NOTE: This will throw on OUT_OF_MEMORY
 //////////////////////////////////////////////////////////////////////////////
 
-  int getMore(uint64_t batchSize);
+  int getMore(uint64_t);
 
 //////////////////////////////////////////////////////////////////////////////
 /// @brief Get next default batchSize many elements.
@@ -109,6 +109,15 @@ struct OperationCursor : public OperationResult {
 //////////////////////////////////////////////////////////////////////////////
 
   int getMore();
+
+//////////////////////////////////////////////////////////////////////////////
+/// @brief Skip the next toSkip many elements.
+///        skipped will be increased by the amount of skipped elements afterwards
+///        Check hasMore()==true before using this
+///        NOTE: This will throw on OUT_OF_MEMORY
+//////////////////////////////////////////////////////////////////////////////
+
+  int skip(uint64_t, uint64_t&);
 };
 
 }

arangod/Utils/Transaction.cpp

@@ -1793,7 +1793,8 @@ OperationCursor Transaction::indexScan(
     return OperationCursor(TRI_ERROR_OUT_OF_MEMORY);
   }
 
-  iterator->skip(skip);
+  uint64_t unused = 0;
+  iterator->skip(skip, unused);
 
   return OperationCursor(transactionContext()->orderCustomTypeHandler(),
                          iterator.release(), limit, batchSize);