Reserve batch size

Author: l0rinc

src/dbwrapper.cpp

@@ -166,6 +166,10 @@ void CDBBatch::Clear()
 {
     m_impl_batch->batch.Clear();
 }
+void CDBBatch::Reserve(size_t size) const
+{
+    m_impl_batch->batch.Reserve(size);
+}
 size_t CDBBatch::ApproximateSize() const
 {
     return m_impl_batch->batch.ApproximateSize();

src/leveldb/db/write_batch.cc

@@ -37,6 +37,10 @@ void WriteBatch::Clear() {
   rep_.resize(kHeader);
 }
 
+void WriteBatch::Reserve(size_t size) {
+  rep_.reserve(size);
+}
+
 size_t WriteBatch::ApproximateSize() const { return rep_.size(); }
 
 Status WriteBatch::Iterate(Handler* handler) const {

src/leveldb/include/leveldb/write_batch.h

@@ -56,6 +56,9 @@ class LEVELDB_EXPORT WriteBatch {
   // Clear all updates buffered in this batch.
   void Clear();
 
+  // Preallocate memory for a batch containing a sequence of updates.
+  void Reserve(size_t size);
+
   // The size of the database changes caused by this batch.
   //
   // This number is tied to implementation details, and may change across

src/txdb.cpp

@@ -92,6 +92,7 @@ std::vector<uint256> CCoinsViewDB::GetHeadBlocks() const {
 
 bool CCoinsViewDB::BatchWrite(CoinsViewCacheCursor& cursor, const uint256 &hashBlock) {
     CDBBatch batch(*m_db);
+    batch.Reserve(m_options.batch_write_bytes);
 
     size_t count = 0;
     size_t changed = 0;