wallet: add option to create in-memory SQLite DB in the migration

src/bench/wallet_migration.cpp

@@ -63,7 +63,7 @@ static void WalletMigration(benchmark::Bench& bench)
 
     bench.epochs(/*numEpochs=*/1).epochIterations(/*numIters=*/1) // run the migration exactly once
          .run([&] {
-             auto res{MigrateLegacyToDescriptor(std::move(wallet), /*passphrase=*/"", *loader->context(), /*was_loaded=*/false)};
+             auto res{MigrateLegacyToDescriptor(std::move(wallet), /*passphrase=*/"", *loader->context(), /*was_loaded=*/false, /*in_memory=*/false)};
              assert(res);
              assert(res->wallet);
              assert(res->watchonly_wallet);

src/wallet/db.h

@@ -184,12 +184,13 @@ public:
 enum class DatabaseFormat {
     SQLITE,
     BERKELEY_RO,
-    BERKELEY_SWAP,
+    BERKELEY_SWAP
 };
 
 struct DatabaseOptions {
     bool require_existing = false;
     bool require_create = false;
+    bool in_memory = false;
     std::optional<DatabaseFormat> require_format;
     uint64_t create_flags = 0;
     SecureString create_passphrase;

src/wallet/sqlite.cpp

@@ -695,7 +695,7 @@ std::unique_ptr<SQLiteDatabase> MakeSQLiteDatabase(const fs::path& path, const D
 {
     try {
         fs::path data_file = SQLiteDataFile(path);
-        auto db = std::make_unique<SQLiteDatabase>(data_file.parent_path(), data_file, options);
+        auto db = std::make_unique<SQLiteDatabase>(data_file.parent_path(), data_file, options, options.in_memory ? true : false);
         if (options.verify && !db->Verify(error)) {
             status = DatabaseStatus::FAILED_VERIFY;
             return nullptr;

src/wallet/wallet.cpp

@@ -4010,7 +4010,7 @@ util::Result<ScriptPubKeyMan*> CWallet::AddWalletDescriptor(WalletDescriptor& de
     return spk_man;
 }
 
-bool CWallet::MigrateToSQLite(bilingual_str& error)
+bool CWallet::MigrateToSQLite(bilingual_str& error, bool in_memory)
 {
     AssertLockHeld(cs_wallet);
 
@@ -4061,6 +4061,7 @@ bool CWallet::MigrateToSQLite(bilingual_str& error)
     DatabaseOptions opts;
     opts.require_create = true;
     opts.require_format = DatabaseFormat::SQLITE;
+    opts.in_memory = in_memory;
     DatabaseStatus db_status;
     std::unique_ptr<WalletDatabase> new_db = MakeDatabase(wallet_path, opts, db_status, error);
     assert(new_db); // This is to prevent doing anything further with this wallet. The original file was deleted, but a backup exists.
@@ -4476,10 +4477,10 @@ util::Result<MigrationResult> MigrateLegacyToDescriptor(const std::string& walle
         return util::Error{Untranslated("Wallet loading failed.") + Untranslated(" ") + error};
     }
 
-    return MigrateLegacyToDescriptor(std::move(local_wallet), passphrase, context, was_loaded);
+    return MigrateLegacyToDescriptor(std::move(local_wallet), passphrase, context, was_loaded, /*in_memory=*/false);
 }
 
-util::Result<MigrationResult> MigrateLegacyToDescriptor(std::shared_ptr<CWallet> local_wallet, const SecureString& passphrase, WalletContext& context, bool was_loaded)
+util::Result<MigrationResult> MigrateLegacyToDescriptor(std::shared_ptr<CWallet> local_wallet, const SecureString& passphrase, WalletContext& context, bool was_loaded, bool in_memory)
 {
     MigrationResult res;
     bilingual_str error;
@@ -4541,7 +4542,7 @@ util::Result<MigrationResult> MigrateLegacyToDescriptor(std::shared_ptr<CWallet>
     {
         LOCK(local_wallet->cs_wallet);
         // First change to using SQLite
-        if (!local_wallet->MigrateToSQLite(error)) return util::Error{error};
+        if (!local_wallet->MigrateToSQLite(error, in_memory)) return util::Error{error};
 
         // Do the migration of keys and scripts for non-empty wallets, and cleanup if it fails
         if (HasLegacyRecords(*local_wallet)) {
@@ -4580,7 +4581,10 @@ util::Result<MigrationResult> MigrateLegacyToDescriptor(std::shared_ptr<CWallet>
         // Migration failed, cleanup
         // Before deleting the wallet's directory, copy the backup file to the top-level wallets dir
         fs::path temp_backup_location = fsbridge::AbsPathJoin(GetWalletDir(), backup_filename);
-        fs::copy_file(backup_path, temp_backup_location, fs::copy_options::none);
+
+        if (!in_memory) {
+            fs::copy_file(backup_path, temp_backup_location, fs::copy_options::none);
+        }
 
         // Make list of wallets to cleanup
         std::vector<std::shared_ptr<CWallet>> created_wallets;
@@ -4625,8 +4629,10 @@ util::Result<MigrationResult> MigrateLegacyToDescriptor(std::shared_ptr<CWallet>
         }
 
         // The wallet directory has been restored, but just in case, copy the previously created backup to the wallet dir
-        fs::copy_file(temp_backup_location, backup_path, fs::copy_options::none);
-        fs::remove(temp_backup_location);
+        if (!in_memory) {
+            fs::copy_file(temp_backup_location, backup_path, fs::copy_options::none);
+            fs::remove(temp_backup_location);
+        }
 
         // Verify that there is no dangling wallet: when the wallet wasn't loaded before, expect null.
         // This check is performed after restoration to avoid an early error before saving the backup.

src/wallet/wallet.h

@@ -1046,7 +1046,7 @@ public:
      * A backup is not created.
      * May crash if something unexpected happens in the filesystem.
      */
-    bool MigrateToSQLite(bilingual_str& error) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
+    bool MigrateToSQLite(bilingual_str& error, bool in_memory = false) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
 
     //! Get all of the descriptors from a legacy wallet
     std::optional<MigrationData> GetDescriptorsForLegacy(bilingual_str& error) const EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
@@ -1137,7 +1137,7 @@ struct MigrationResult {
 //! Do all steps to migrate a legacy wallet to a descriptor wallet
 [[nodiscard]] util::Result<MigrationResult> MigrateLegacyToDescriptor(const std::string& wallet_name, const SecureString& passphrase, WalletContext& context);
 //! Requirement: The wallet provided to this function must be isolated, with no attachment to the node's context.
-[[nodiscard]] util::Result<MigrationResult> MigrateLegacyToDescriptor(std::shared_ptr<CWallet> local_wallet, const SecureString& passphrase, WalletContext& context, bool was_loaded);
+[[nodiscard]] util::Result<MigrationResult> MigrateLegacyToDescriptor(std::shared_ptr<CWallet> local_wallet, const SecureString& passphrase, WalletContext& context, bool was_loaded, bool in_memory);
 } // namespace wallet
 
 #endif // BITCOIN_WALLET_WALLET_H

src/wallet/walletdb.cpp

@@ -1427,7 +1427,7 @@ std::unique_ptr<WalletDatabase> MakeDatabase(const fs::path& path, const Databas
 {
     bool exists;
     try {
-        exists = fs::symlink_status(path).type() != fs::file_type::not_found;
+        exists = fs::symlink_status(path).type() != fs::file_type::not_found && !options.in_memory;
     } catch (const fs::filesystem_error& e) {
         error = Untranslated(strprintf("Failed to access database path '%s': %s", fs::PathToString(path), fsbridge::get_filesystem_error_message(e)));
         status = DatabaseStatus::FAILED_BAD_PATH;