Merge #19325: wallet: Refactor BerkeleyDatabase to introduce DatabaseBatch abstract class

b82f0ca4d5 walletdb: Add MakeBatch function to BerkeleyDatabase and use it (Andrew Chow)
eac9200814 walletdb: Refactor DatabaseBatch abstract class from BerkeleyBatch (Andrew Chow)

Pull request description:

  In order to support alternative database systems, we need to have a generic `Batch` class. This PR adds a `DatabaseBatch` abstract class which is implemented by `BerkeleyBatch`. `DatabaseBatch` is now the class that is used by `WalletBatch` to interact with the database. To be able to get the correct type of `DatabaseBatch`, `BerkeleyDatabase` now has a `MakeBatch` function which returns a newly constructed `std::unique_ptr<DatabaseBatch>`. For `BerkeleyDatabase`, that will be `std::unique_ptr<BerkeleyBatch>`.

  The `Read`, `Write`, `Erase`, and `Exists` template functions are moved from `BerkeleyBatch`.

  Part of #18971

  Requires #19308 and #19324

ACKs for top commit:
  Sjors:
    re-utACK b82f0ca4d5
  MarcoFalke:
    ACK b82f0ca4d5 🌘
  meshcollider:
    LGTM, utACK b82f0ca4d5

Tree-SHA512: 6d2d41631c0983391dbecd702e881c6775b155c90b275df97f7157e42608ed251744f9d7ce5173d02a6c5cc38d90b611880fac7fa635d3d8c4d590681f56ac6a

src/wallet/bdb.h

@@ -93,6 +93,8 @@ std::shared_ptr<BerkeleyEnvironment> GetWalletEnv(const fs::path& wallet_path, s
 /** Return whether a BDB wallet database is currently loaded. */
 bool IsBDBWalletLoaded(const fs::path& wallet_path);
 
+class BerkeleyBatch;
+
 /** An instance of this class represents one database.
  * For BerkeleyDB this is just a (env, strFile) tuple.
  **/
@@ -161,6 +163,9 @@ public:
     /** Database pointer. This is initialized lazily and reset during flushes, so it can be null. */
     std::unique_ptr<Db> m_db;
 
+    /** Make a BerkeleyBatch connected to this database */
+    std::unique_ptr<BerkeleyBatch> MakeBatch(const char* mode, bool flush_on_close);
+
 private:
     std::string strFile;
 
@@ -172,7 +177,7 @@ private:
 };
 
 /** RAII class that provides access to a Berkeley database */
-class BerkeleyBatch
+class BerkeleyBatch : public DatabaseBatch
 {
     /** RAII class that automatically cleanses its data on destruction */
     class SafeDbt final
@@ -195,10 +200,10 @@ class BerkeleyBatch
     };
 
 private:
-    bool ReadKey(CDataStream&& key, CDataStream& value);
-    bool WriteKey(CDataStream&& key, CDataStream&& value, bool overwrite = true);
-    bool EraseKey(CDataStream&& key);
-    bool HasKey(CDataStream&& key);
+    bool ReadKey(CDataStream&& key, CDataStream& value) override;
+    bool WriteKey(CDataStream&& key, CDataStream&& value, bool overwrite = true) override;
+    bool EraseKey(CDataStream&& key) override;
+    bool HasKey(CDataStream&& key) override;
 
 protected:
     Db* pdb;
@@ -211,71 +216,20 @@ protected:
 
 public:
     explicit BerkeleyBatch(BerkeleyDatabase& database, const char* pszMode = "r+", bool fFlushOnCloseIn=true);
-    ~BerkeleyBatch() { Close(); }
+    ~BerkeleyBatch() override { Close(); }
 
     BerkeleyBatch(const BerkeleyBatch&) = delete;
     BerkeleyBatch& operator=(const BerkeleyBatch&) = delete;
 
-    void Flush();
-    void Close();
+    void Flush() override;
+    void Close() override;
 
-    template <typename K, typename T>
-    bool Read(const K& key, T& value)
-    {
-        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
-        ssKey.reserve(1000);
-        ssKey << key;
-
-        CDataStream ssValue(SER_DISK, CLIENT_VERSION);
-        if (!ReadKey(std::move(ssKey), ssValue)) return false;
-        try {
-            ssValue >> value;
-            return true;
-        } catch (const std::exception&) {
-            return false;
-        }
-    }
-
-    template <typename K, typename T>
-    bool Write(const K& key, const T& value, bool fOverwrite = true)
-    {
-        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
-        ssKey.reserve(1000);
-        ssKey << key;
-
-        CDataStream ssValue(SER_DISK, CLIENT_VERSION);
-        ssValue.reserve(10000);
-        ssValue << value;
-
-        return WriteKey(std::move(ssKey), std::move(ssValue), fOverwrite);
-    }
-
-    template <typename K>
-    bool Erase(const K& key)
-    {
-        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
-        ssKey.reserve(1000);
-        ssKey << key;
-
-        return EraseKey(std::move(ssKey));
-    }
-
-    template <typename K>
-    bool Exists(const K& key)
-    {
-        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
-        ssKey.reserve(1000);
-        ssKey << key;
-
-        return HasKey(std::move(ssKey));
-    }
-
-    bool StartCursor();
-    bool ReadAtCursor(CDataStream& ssKey, CDataStream& ssValue, bool& complete);
-    void CloseCursor();
-    bool TxnBegin();
-    bool TxnCommit();
-    bool TxnAbort();
+    bool StartCursor() override;
+    bool ReadAtCursor(CDataStream& ssKey, CDataStream& ssValue, bool& complete) override;
+    void CloseCursor() override;
+    bool TxnBegin() override;
+    bool TxnCommit() override;
+    bool TxnAbort() override;
 };
 
 std::string BerkeleyDatabaseVersion();