From 751077c6e25e010cff85fe9793a8c5b843350f98 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?L=C5=91rinc?= <pap.lorinc@gmail.com>
Date: Tue, 1 Apr 2025 15:46:23 +0200
Subject: [PATCH] Coins: Add `kHeader` to `CDBBatch::size_estimate`

The initialization of the manual `size_estimate` in `CDBBatch::Clear()` is corrected from `0` to `kHeader` (LevelDB's fixed batch header size).
This aligns the manual estimate with LevelDB's actual size immediately after clearing, fixing discrepancies that would otherwise be caught by tests in the next commit (e.g., `coins_tests`, `validation_chainstatemanager_tests`).
---
 src/dbwrapper.cpp | 8 ++++++--
 src/dbwrapper.h   | 2 ++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/dbwrapper.cpp b/src/dbwrapper.cpp
index b3faff10cea..f4935c4f357 100644
--- a/src/dbwrapper.cpp
+++ b/src/dbwrapper.cpp
@@ -158,14 +158,18 @@ struct CDBBatch::WriteBatchImpl {
 
 CDBBatch::CDBBatch(const CDBWrapper& _parent)
     : parent{_parent},
-      m_impl_batch{std::make_unique<CDBBatch::WriteBatchImpl>()} {};
+      m_impl_batch{std::make_unique<CDBBatch::WriteBatchImpl>()}
+{
+    Clear();
+};
 
 CDBBatch::~CDBBatch() = default;
 
 void CDBBatch::Clear()
 {
     m_impl_batch->batch.Clear();
-    size_estimate = 0;
+    assert(m_impl_batch->batch.ApproximateSize() == kHeader);
+    size_estimate = kHeader; // TODO remove
 }
 
 void CDBBatch::WriteImpl(std::span<const std::byte> key, DataStream& ssValue)
diff --git a/src/dbwrapper.h b/src/dbwrapper.h
index 98446361e4e..1ff7dc1d2ee 100644
--- a/src/dbwrapper.h
+++ b/src/dbwrapper.h
@@ -75,6 +75,8 @@ class CDBBatch
     friend class CDBWrapper;
 
 private:
+    static constexpr size_t kHeader{12}; // See: src/leveldb/db/write_batch.cc#L27
+
     const CDBWrapper &parent;
 
     struct WriteBatchImpl;