wallet: take use of FastWalletRescanFilter

Can be reviewed with `--ignore-all-space`.

Author: theStack

src/wallet/wallet.cpp

@@ -1814,7 +1814,11 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
     uint256 block_hash = start_block;
     ScanResult result;
 
-    WalletLogPrintf("Rescan started from block %s...\n", start_block.ToString());
+    std::unique_ptr<FastWalletRescanFilter> fast_rescan_filter;
+    if (!IsLegacy() && chain().hasBlockFilterIndex(BlockFilterType::BASIC)) fast_rescan_filter = std::make_unique<FastWalletRescanFilter>(*this);
+
+    WalletLogPrintf("Rescan started from block %s... (%s)\n", start_block.ToString(),
+                    fast_rescan_filter ? "fast variant using block filters" : "slow variant inspecting all blocks");
 
     fAbortRescan = false;
     ShowProgress(strprintf("%s " + _("Rescanning…").translated, GetDisplayName()), 0); // show rescan progress in GUI as dialog or on splashscreen, if rescan required on startup (e.g. due to corruption)
@@ -1841,9 +1845,16 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
             WalletLogPrintf("Still rescanning. At block %d. Progress=%f\n", block_height, progress_current);
         }
 
-        // Read block data
-        CBlock block;
-        chain().findBlock(block_hash, FoundBlock().data(block));
+        bool fetch_block{true};
+        if (fast_rescan_filter) {
+            fast_rescan_filter->UpdateIfNeeded();
+            auto matches_block{fast_rescan_filter->MatchesBlock(block_hash)};
+            if (matches_block.has_value() && !*matches_block) {
+                result.last_scanned_block = block_hash;
+                result.last_scanned_height = block_height;
+                fetch_block = false;
+            }
+        }
 
         // Find next block separately from reading data above, because reading
         // is slow and there might be a reorg while it is read.
@@ -1852,35 +1863,41 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
         uint256 next_block_hash;
         chain().findBlock(block_hash, FoundBlock().inActiveChain(block_still_active).nextBlock(FoundBlock().inActiveChain(next_block).hash(next_block_hash)));
 
-        if (!block.IsNull()) {
-            LOCK(cs_wallet);
-            if (!block_still_active) {
-                // Abort scan if current block is no longer active, to prevent
-                // marking transactions as coming from the wrong block.
-                result.last_failed_block = block_hash;
-                result.status = ScanResult::FAILURE;
-                break;
-            }
-            for (size_t posInBlock = 0; posInBlock < block.vtx.size(); ++posInBlock) {
-                SyncTransaction(block.vtx[posInBlock], TxStateConfirmed{block_hash, block_height, static_cast<int>(posInBlock)}, fUpdate, /*rescanning_old_block=*/true);
-            }
-            // scan succeeded, record block as most recent successfully scanned
-            result.last_scanned_block = block_hash;
-            result.last_scanned_height = block_height;
+        if (fetch_block) {
+            // Read block data
+            CBlock block;
+            chain().findBlock(block_hash, FoundBlock().data(block));
+
+            if (!block.IsNull()) {
+                LOCK(cs_wallet);
+                if (!block_still_active) {
+                    // Abort scan if current block is no longer active, to prevent
+                    // marking transactions as coming from the wrong block.
+                    result.last_failed_block = block_hash;
+                    result.status = ScanResult::FAILURE;
+                    break;
+                }
+                for (size_t posInBlock = 0; posInBlock < block.vtx.size(); ++posInBlock) {
+                    SyncTransaction(block.vtx[posInBlock], TxStateConfirmed{block_hash, block_height, static_cast<int>(posInBlock)}, fUpdate, /*rescanning_old_block=*/true);
+                }
+                // scan succeeded, record block as most recent successfully scanned
+                result.last_scanned_block = block_hash;
+                result.last_scanned_height = block_height;
 
-            if (save_progress && next_interval) {
-                CBlockLocator loc = m_chain->getActiveChainLocator(block_hash);
+                if (save_progress && next_interval) {
+                    CBlockLocator loc = m_chain->getActiveChainLocator(block_hash);
 
-                if (!loc.IsNull()) {
-                    WalletLogPrintf("Saving scan progress %d.\n", block_height);
-                    WalletBatch batch(GetDatabase());
-                    batch.WriteBestBlock(loc);
+                    if (!loc.IsNull()) {
+                        WalletLogPrintf("Saving scan progress %d.\n", block_height);
+                        WalletBatch batch(GetDatabase());
+                        batch.WriteBestBlock(loc);
+                    }
                 }
+            } else {
+                // could not scan block, keep scanning but record this block as the most recent failure
+                result.last_failed_block = block_hash;
+                result.status = ScanResult::FAILURE;
             }
-        } else {
-            // could not scan block, keep scanning but record this block as the most recent failure
-            result.last_failed_block = block_hash;
-            result.status = ScanResult::FAILURE;
         }
         if (max_height && block_height >= *max_height) {
             break;