Use a single wallet batch for UpgradeKeyMetadata

src/wallet/wallet.cpp

@@ -371,6 +371,8 @@ void CWallet::UpgradeKeyMetadata()
         return;
     }
 
+    std::unique_ptr<WalletBatch> batch = MakeUnique<WalletBatch>(*database);
+    size_t cnt = 0;
     for (auto& meta_pair : mapKeyMetadata) {
         CKeyMetadata& meta = meta_pair.second;
         if (!meta.hd_seed_id.IsNull() && !meta.has_key_origin && meta.hdKeypath != "s") { // If the hdKeypath is "s", that's the seed and it doesn't have a key origin
@@ -392,10 +394,15 @@ void CWallet::UpgradeKeyMetadata()
             // Write meta to wallet
             CPubKey pubkey;
             if (GetPubKey(meta_pair.first, pubkey)) {
-                WriteKeyMetadata(meta, pubkey, true);
+                batch->WriteKeyMetadata(meta, pubkey, true);
+                if (++cnt % 1000 == 0) {
+                    // avoid creating overlarge in-memory batches in case the wallet contains large amounts of keys
+                    batch.reset(new WalletBatch(*database));
+                }
             }
         }
     }
+    batch.reset(); //write before setting the flag
     SetWalletFlag(WALLET_FLAG_KEY_ORIGIN_METADATA);
 }