diff --git a/src/txdb.h b/src/txdb.h
--- a/src/txdb.h
+++ b/src/txdb.h
@@ -156,6 +156,11 @@
/// Write block locator of the chain that the txindex is in sync with.
bool WriteBestBlock(const CBlockLocator &locator);
+
+ /// Migrate txindex data from the block tree DB, where it may be for older
+ /// nodes that have not been upgraded yet to the new database.
+ bool MigrateData(CBlockTreeDB &block_tree_db,
+ const CBlockLocator &best_locator);
};
#endif // BITCOIN_TXDB_H
diff --git a/src/txdb.cpp b/src/txdb.cpp
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -22,6 +22,7 @@
static const char DB_COINS = 'c';
static const char DB_BLOCK_FILES = 'f';
static const char DB_TXINDEX = 't';
+static const char DB_TXINDEX_BLOCK = 'T';
static const char DB_BLOCK_INDEX = 'b';
static const char DB_BEST_BLOCK = 'B';
@@ -483,3 +484,145 @@
bool TxIndexDB::WriteBestBlock(const CBlockLocator &locator) {
return Write(DB_BEST_BLOCK, locator);
}
+
+/*
+ * Safely persist a transfer of data from the old txindex database to the new
+ * one, and compact the range of keys updated. This is used internally by
+ * MigrateData.
+ */
+static void
+WriteTxIndexMigrationBatches(TxIndexDB &newdb, CBlockTreeDB &olddb,
+ CDBBatch &batch_newdb, CDBBatch &batch_olddb,
+ const std::pair<unsigned char, uint256> &begin_key,
+ const std::pair<unsigned char, uint256> &end_key) {
+ // Sync new DB changes to disk before deleting from old DB.
+ newdb.WriteBatch(batch_newdb, /*fSync=*/true);
+ olddb.WriteBatch(batch_olddb);
+ olddb.CompactRange(begin_key, end_key);
+
+ batch_newdb.Clear();
+ batch_olddb.Clear();
+}
+
+bool TxIndexDB::MigrateData(CBlockTreeDB &block_tree_db,
+ const CBlockLocator &best_locator) {
+ // The prior implementation of txindex was always in sync with block index
+ // and presence was indicated with a boolean DB flag. If the flag is set,
+ // this means the txindex from a previous version is valid and in sync with
+ // the chain tip. The first step of the migration is to unset the flag and
+ // write the chain hash to a separate key, DB_TXINDEX_BLOCK. After that, the
+ // index entries are copied over in batches to the new database. Finally,
+ // DB_TXINDEX_BLOCK is erased from the old database and the block hash is
+ // written to the new database.
+ //
+ // Unsetting the boolean flag ensures that if the node is downgraded to a
+ // previous version, it will not see a corrupted, partially migrated index
+ // -- it will see that the txindex is disabled. When the node is upgraded
+ // again, the migration will pick up where it left off and sync to the block
+ // with hash DB_TXINDEX_BLOCK.
+ bool f_legacy_flag = false;
+ block_tree_db.ReadFlag("txindex", f_legacy_flag);
+ if (f_legacy_flag) {
+ if (!block_tree_db.Write(DB_TXINDEX_BLOCK, best_locator)) {
+ return error("%s: cannot write block indicator", __func__);
+ }
+ if (!block_tree_db.WriteFlag("txindex", false)) {
+ return error("%s: cannot write block index db flag", __func__);
+ }
+ }
+
+ CBlockLocator locator;
+ if (!block_tree_db.Read(DB_TXINDEX_BLOCK, locator)) {
+ return true;
+ }
+
+ int64_t count = 0;
+ LogPrintf("Upgrading txindex database... [0%%]\n");
+ uiInterface.ShowProgress(_("Upgrading txindex database"), 0, true);
+ int report_done = 0;
+ const size_t batch_size = 1 << 24; // 16 MiB
+
+ CDBBatch batch_newdb(*this);
+ CDBBatch batch_olddb(block_tree_db);
+
+ std::pair<unsigned char, uint256> key;
+ std::pair<unsigned char, uint256> begin_key{DB_TXINDEX, uint256()};
+ std::pair<unsigned char, uint256> prev_key = begin_key;
+
+ bool interrupted = false;
+ std::unique_ptr<CDBIterator> cursor(block_tree_db.NewIterator());
+ for (cursor->Seek(begin_key); cursor->Valid(); cursor->Next()) {
+ boost::this_thread::interruption_point();
+ if (ShutdownRequested()) {
+ interrupted = true;
+ break;
+ }
+
+ if (!cursor->GetKey(key)) {
+ return error("%s: cannot get key from valid cursor", __func__);
+ }
+ if (key.first != DB_TXINDEX) {
+ break;
+ }
+
+ // Log progress every 10%.
+ if (++count % 256 == 0) {
+ // Since txids are uniformly random and traversed in increasing
+ // order, the high 16 bits of the hash can be used to estimate the
+ // current progress.
+ const uint256 &txid = key.second;
+ uint32_t high_nibble =
+ (static_cast<uint32_t>(*(txid.begin() + 0)) << 8) +
+ (static_cast<uint32_t>(*(txid.begin() + 1)) << 0);
+ int percentage_done = (int)(high_nibble * 100.0 / 65536.0 + 0.5);
+
+ uiInterface.ShowProgress(_("Upgrading txindex database"),
+ percentage_done, true);
+ if (report_done < percentage_done / 10) {
+ LogPrintf("Upgrading txindex database... [%d%%]\n",
+ percentage_done);
+ report_done = percentage_done / 10;
+ }
+ }
+
+ CDiskTxPos value;
+ if (!cursor->GetValue(value)) {
+ return error("%s: cannot parse txindex record", __func__);
+ }
+ batch_newdb.Write(key, value);
+ batch_olddb.Erase(key);
+
+ if (batch_newdb.SizeEstimate() > batch_size ||
+ batch_olddb.SizeEstimate() > batch_size) {
+ // NOTE: it's OK to delete the key pointed at by the current DB
+ // cursor while iterating because LevelDB iterators are guaranteed
+ // to provide a consistent view of the underlying data, like a
+ // lightweight snapshot.
+ WriteTxIndexMigrationBatches(*this, block_tree_db, batch_newdb,
+ batch_olddb, prev_key, key);
+ prev_key = key;
+ }
+ }
+
+ // If these final DB batches complete the migration, write the best block
+ // hash marker to the new database and delete from the old one. This signals
+ // that the former is fully caught up to that point in the blockchain and
+ // that all txindex entries have been removed from the latter.
+ if (!interrupted) {
+ batch_olddb.Erase(DB_TXINDEX_BLOCK);
+ batch_newdb.Write(DB_BEST_BLOCK, locator);
+ }
+
+ WriteTxIndexMigrationBatches(*this, block_tree_db, batch_newdb, batch_olddb,
+ begin_key, key);
+
+ if (interrupted) {
+ LogPrintf("[CANCELLED].\n");
+ return false;
+ }
+
+ uiInterface.ShowProgress("", 100, false);
+
+ LogPrintf("[DONE].\n");
+ return true;
+}