Merge bitcoin#15433: Use a single wallet batch for UpgradeKeyMetadata

0bedcba Use a single wallet batch for UpgradeKeyMetadata (Jonas Schnelli)

Pull request description:

  Opening wallets (the first time) after bitcoin#14021 took on my end around 30 seconds due to the keymetadata migration (tested on regtest).

  Using a single wallet batch reduces the required time for the migration down to <1s on my system for a default 2k keypool wallet.

Tree-SHA512: f68739e452d382f5294186f47511b94884a1a0868688dd3179034a7e091a67f93bc9dd45cdfc9fa6b1fe90362772b719278012f2f56b752b803c87db8597a7b0

src/wallet/wallet.cpp

@@ -519,6 +519,8 @@ 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
@@ -540,10 +542,15 @@ 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);
 }