From c0c94ec9860ac121e342e6c2102ffaf30630c244 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?L=C5=91rinc?= <pap.lorinc@gmail.com>
Date: Wed, 14 Jan 2026 23:48:48 +0100
Subject: [PATCH] dbwrapper: have `Read` and `Exists` reuse `ReadRaw`

`ExistsImpl` was removed since it duplicates `CDBWrapper::ReadImpl`.
The only difference is that `ExistsImpl` discards the value while `ReadImpl` returns it as `std::string`.
In this series, `HaveCoin` database lookups go through `GetCoin`/`Read`, and successful reads are cached in `CCoinsViewCache`, so this copy is not a separate recurring cost.
`CDBWrapper::Exists()` and `::ReadRaw()` both issue a LevelDB `::Get`.

Introduce a small helper returning the raw value bytes (as `std::string`) for a given key.
Move `Exists` closer to the read methods.
---
 src/dbwrapper.cpp | 15 ---------------
 src/dbwrapper.h   | 28 +++++++++++++++-------------
 2 files changed, 15 insertions(+), 28 deletions(-)

diff --git a/src/dbwrapper.cpp b/src/dbwrapper.cpp
index eb222078b5e..d9fa63badef 100644
--- a/src/dbwrapper.cpp
+++ b/src/dbwrapper.cpp
@@ -316,21 +316,6 @@ std::optional<std::string> CDBWrapper::ReadImpl(std::span<const std::byte> key)
     return strValue;
 }
 
-bool CDBWrapper::ExistsImpl(std::span<const std::byte> key) const
-{
-    leveldb::Slice slKey(CharCast(key.data()), key.size());
-
-    std::string strValue;
-    leveldb::Status status = DBContext().pdb->Get(DBContext().readoptions, slKey, &strValue);
-    if (!status.ok()) {
-        if (status.IsNotFound())
-            return false;
-        LogError("LevelDB read failure: %s", status.ToString());
-        HandleError(status);
-    }
-    return true;
-}
-
 size_t CDBWrapper::EstimateSizeImpl(std::span<const std::byte> key1, std::span<const std::byte> key2) const
 {
     leveldb::Slice slKey1(CharCast(key1.data()), key1.size());
diff --git a/src/dbwrapper.h b/src/dbwrapper.h
index 2eee6c1c023..b89a099b58f 100644
--- a/src/dbwrapper.h
+++ b/src/dbwrapper.h
@@ -192,7 +192,6 @@ private:
     inline static const std::string OBFUSCATION_KEY{"\000obfuscate_key", 14}; // explicit size to avoid truncation at leading \0
 
     std::optional<std::string> ReadImpl(std::span<const std::byte> key) const;
-    bool ExistsImpl(std::span<const std::byte> key) const;
     size_t EstimateSizeImpl(std::span<const std::byte> key1, std::span<const std::byte> key2) const;
     auto& DBContext() const LIFETIMEBOUND { return *Assert(m_db_context); }
 
@@ -203,13 +202,19 @@ public:
     CDBWrapper(const CDBWrapper&) = delete;
     CDBWrapper& operator=(const CDBWrapper&) = delete;
 
-    template <typename K, typename V>
-    bool Read(const K& key, V& value) const
+    template <typename K>
+    std::optional<std::string> ReadRaw(const K& key) const
     {
         DataStream ssKey{};
         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey << key;
-        std::optional<std::string> strValue{ReadImpl(ssKey)};
+        return ReadImpl(ssKey);
+    }
+
+    template <typename K, typename V>
+    bool Read(const K& key, V& value) const
+    {
+        auto strValue{ReadRaw(key)};
         if (!strValue) {
             return false;
         }
@@ -223,6 +228,12 @@ public:
         return true;
     }
 
+    template <typename K>
+    bool Exists(const K& key) const
+    {
+        return !!ReadRaw(key);
+    }
+
     template <typename K, typename V>
     void Write(const K& key, const V& value, bool fSync = false)
     {
@@ -231,15 +242,6 @@ public:
         WriteBatch(batch, fSync);
     }
 
-    template <typename K>
-    bool Exists(const K& key) const
-    {
-        DataStream ssKey{};
-        ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
-        ssKey << key;
-        return ExistsImpl(ssKey);
-    }
-
     template <typename K>
     void Erase(const K& key, bool fSync = false)
     {