index: Move index DBs into index/ directory.

6 files changed, 264 insertions, 245 deletions

diff --git a/src/index/base.cpp b/src/index/base.cpp
index f381681a64..738166dc94 100644
--- a/src/index/base.cpp
+++ b/src/index/base.cpp
@@ -11,6 +11,8 @@
 #include <validation.h>
 #include <warnings.h>
 
+constexpr char DB_BEST_BLOCK = 'B';
+
 constexpr int64_t SYNC_LOG_INTERVAL = 30; // seconds
 constexpr int64_t SYNC_LOCATOR_WRITE_INTERVAL = 30; // seconds
 
@@ -26,6 +28,24 @@ static void FatalError(const char* fmt, const Args&... args)
     StartShutdown();
 }
 
+BaseIndex::DB::DB(const fs::path& path, size_t n_cache_size, bool f_memory, bool f_wipe, bool f_obfuscate) :
+    CDBWrapper(path, n_cache_size, f_memory, f_wipe, f_obfuscate)
+{}
+
+bool BaseIndex::DB::ReadBestBlock(CBlockLocator& locator) const
+{
+    bool success = Read(DB_BEST_BLOCK, locator);
+    if (!success) {
+        locator.SetNull();
+    }
+    return success;
+}
+
+bool BaseIndex::DB::WriteBestBlock(const CBlockLocator& locator)
+{
+    return Write(DB_BEST_BLOCK, locator);
+}
+
 BaseIndex::~BaseIndex()
 {
     Interrupt();
diff --git a/src/index/base.h b/src/index/base.h
index 68efaaaf26..04ee6e6cc2 100644
--- a/src/index/base.h
+++ b/src/index/base.h
@@ -5,10 +5,10 @@
 #ifndef BITCOIN_INDEX_BASE_H
 #define BITCOIN_INDEX_BASE_H
 
+#include <dbwrapper.h>
 #include <primitives/block.h>
 #include <primitives/transaction.h>
 #include <threadinterrupt.h>
-#include <txdb.h>
 #include <uint256.h>
 #include <validationinterface.h>
 
@@ -21,6 +21,20 @@ class CBlockIndex;
  */
 class BaseIndex : public CValidationInterface
 {
+protected:
+    class DB : public CDBWrapper
+    {
+    public:
+        DB(const fs::path& path, size_t n_cache_size,
+           bool f_memory = false, bool f_wipe = false, bool f_obfuscate = false);
+
+        /// Read block locator of the chain that the txindex is in sync with.
+        bool ReadBestBlock(CBlockLocator& locator) const;
+
+        /// Write block locator of the chain that the txindex is in sync with.
+        bool WriteBestBlock(const CBlockLocator& locator);
+    };
+
 private:
     /// Whether the index is in sync with the main chain. The flag is flipped
     /// from false to true once, after which point this starts processing
@@ -55,7 +69,7 @@ protected:
     /// Write update index entries for a newly connected block.
     virtual bool WriteBlock(const CBlock& block, const CBlockIndex* pindex) { return true; }
 
-    virtual BaseIndexDB& GetDB() const = 0;
+    virtual DB& GetDB() const = 0;
 
     /// Get the name of the index for display in logs.
     virtual const char* GetName() const = 0;
diff --git a/src/index/txindex.cpp b/src/index/txindex.cpp
index 328039977f..e106b9b420 100644
--- a/src/index/txindex.cpp
+++ b/src/index/txindex.cpp
@@ -3,15 +3,232 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <index/txindex.h>
+#include <init.h>
+#include <ui_interface.h>
 #include <util.h>
 #include <validation.h>
 
+#include <boost/thread.hpp>
+
+constexpr char DB_BEST_BLOCK = 'B';
+constexpr char DB_TXINDEX = 't';
+constexpr char DB_TXINDEX_BLOCK = 'T';
+
 std::unique_ptr<TxIndex> g_txindex;
 
+struct CDiskTxPos : public CDiskBlockPos
+{
+    unsigned int nTxOffset; // after header
+
+    ADD_SERIALIZE_METHODS;
+
+    template <typename Stream, typename Operation>
+    inline void SerializationOp(Stream& s, Operation ser_action) {
+        READWRITEAS(CDiskBlockPos, *this);
+        READWRITE(VARINT(nTxOffset));
+    }
+
+    CDiskTxPos(const CDiskBlockPos &blockIn, unsigned int nTxOffsetIn) : CDiskBlockPos(blockIn.nFile, blockIn.nPos), nTxOffset(nTxOffsetIn) {
+    }
+
+    CDiskTxPos() {
+        SetNull();
+    }
+
+    void SetNull() {
+        CDiskBlockPos::SetNull();
+        nTxOffset = 0;
+    }
+};
+
+/**
+ * Access to the txindex database (indexes/txindex/)
+ *
+ * The database stores a block locator of the chain the database is synced to
+ * so that the TxIndex can efficiently determine the point it last stopped at.
+ * A locator is used instead of a simple hash of the chain tip because blocks
+ * and block index entries may not be flushed to disk until after this database
+ * is updated.
+ */
+class TxIndex::DB : public BaseIndex::DB
+{
+public:
+    explicit DB(size_t n_cache_size, bool f_memory = false, bool f_wipe = false);
+
+    /// Read the disk location of the transaction data with the given hash. Returns false if the
+    /// transaction hash is not indexed.
+    bool ReadTxPos(const uint256& txid, CDiskTxPos& pos) const;
+
+    /// Write a batch of transaction positions to the DB.
+    bool WriteTxs(const std::vector<std::pair<uint256, CDiskTxPos>>& v_pos);
+
+    /// 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);
+};
+
+TxIndex::DB::DB(size_t n_cache_size, bool f_memory, bool f_wipe) :
+    BaseIndex::DB(GetDataDir() / "indexes" / "txindex", n_cache_size, f_memory, f_wipe)
+{}
+
+bool TxIndex::DB::ReadTxPos(const uint256 &txid, CDiskTxPos& pos) const
+{
+    return Read(std::make_pair(DB_TXINDEX, txid), pos);
+}
+
+bool TxIndex::DB::WriteTxs(const std::vector<std::pair<uint256, CDiskTxPos>>& v_pos)
+{
+    CDBBatch batch(*this);
+    for (const auto& tuple : v_pos) {
+        batch.Write(std::make_pair(DB_TXINDEX, tuple.first), tuple.second);
+    }
+    return WriteBatch(batch);
+}
+
+/*
+ * 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(CDBWrapper& newdb, CDBWrapper& 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 TxIndex::DB::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;
+}
+
 TxIndex::TxIndex(size_t n_cache_size, bool f_memory, bool f_wipe)
     : m_db(MakeUnique<TxIndex::DB>(n_cache_size, f_memory, f_wipe))
 {}
 
+TxIndex::~TxIndex() {}
+
 bool TxIndex::Init()
 {
     LOCK(cs_main);
@@ -38,7 +255,7 @@ bool TxIndex::WriteBlock(const CBlock& block, const CBlockIndex* pindex)
     return m_db->WriteTxs(vPos);
 }
 
-BaseIndexDB& TxIndex::GetDB() const { return *m_db; }
+BaseIndex::DB& TxIndex::GetDB() const { return *m_db; }
 
 bool TxIndex::FindTx(const uint256& tx_hash, uint256& block_hash, CTransactionRef& tx) const
 {
diff --git a/src/index/txindex.h b/src/index/txindex.h
index 2a0c70e9d1..8202c3c951 100644
--- a/src/index/txindex.h
+++ b/src/index/txindex.h
@@ -5,7 +5,9 @@
 #ifndef BITCOIN_INDEX_TXINDEX_H
 #define BITCOIN_INDEX_TXINDEX_H
 
+#include <chain.h>
 #include <index/base.h>
+#include <txdb.h>
 
 /**
  * TxIndex is used to look up transactions included in the blockchain by hash.
@@ -14,8 +16,11 @@
  */
 class TxIndex final : public BaseIndex
 {
+protected:
+    class DB;
+
 private:
-    const std::unique_ptr<TxIndexDB> m_db;
+    const std::unique_ptr<DB> m_db;
 
 protected:
     /// Override base class init to migrate from old database.
@@ -23,7 +28,7 @@ protected:
 
     bool WriteBlock(const CBlock& block, const CBlockIndex* pindex) override;
 
-    BaseIndexDB& GetDB() const override;
+    BaseIndex::DB& GetDB() const override;
 
     const char* GetName() const override { return "txindex"; }
 
@@ -31,6 +36,9 @@ public:
     /// Constructs the index, which becomes available to be queried.
     explicit TxIndex(size_t n_cache_size, bool f_memory = false, bool f_wipe = false);
 
+    // Destructor is declared because this class contains a unique_ptr to an incomplete type.
+    virtual ~TxIndex() override;
+
     /// Look up a transaction by hash.
     ///
     /// @param[in]   tx_hash  The hash of the transaction to be returned.
diff --git a/src/txdb.cpp b/src/txdb.cpp
index 624b23962a..b1d5879c83 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -21,8 +21,6 @@
 static const char DB_COIN = 'C';
 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';
@@ -414,177 +412,3 @@ bool CCoinsViewDB::Upgrade() {
     LogPrintf("[%s].\n", ShutdownRequested() ? "CANCELLED" : "DONE");
     return !ShutdownRequested();
 }
-
-BaseIndexDB::BaseIndexDB(const fs::path& path, size_t n_cache_size, bool f_memory, bool f_wipe, bool f_obfuscate) :
-    CDBWrapper(path, n_cache_size, f_memory, f_wipe, f_obfuscate)
-{}
-
-TxIndexDB::TxIndexDB(size_t n_cache_size, bool f_memory, bool f_wipe) :
-    BaseIndexDB(GetDataDir() / "indexes" / "txindex", n_cache_size, f_memory, f_wipe)
-{}
-
-bool TxIndexDB::ReadTxPos(const uint256 &txid, CDiskTxPos& pos) const
-{
-    return Read(std::make_pair(DB_TXINDEX, txid), pos);
-}
-
-bool TxIndexDB::WriteTxs(const std::vector<std::pair<uint256, CDiskTxPos>>& v_pos)
-{
-    CDBBatch batch(*this);
-    for (const auto& tuple : v_pos) {
-        batch.Write(std::make_pair(DB_TXINDEX, tuple.first), tuple.second);
-    }
-    return WriteBatch(batch);
-}
-
-bool BaseIndexDB::ReadBestBlock(CBlockLocator& locator) const
-{
-    bool success = Read(DB_BEST_BLOCK, locator);
-    if (!success) {
-        locator.SetNull();
-    }
-    return success;
-}
-
-bool BaseIndexDB::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;
-}
diff --git a/src/txdb.h b/src/txdb.h
index f9d9e4246c..100adb428d 100644
--- a/src/txdb.h
+++ b/src/txdb.h
@@ -40,31 +40,6 @@ static const int64_t nMaxTxIndexCache = 1024;
 //! Max memory allocated to coin DB specific cache (MiB)
 static const int64_t nMaxCoinsDBCache = 8;
 
-struct CDiskTxPos : public CDiskBlockPos
-{
-    unsigned int nTxOffset; // after header
-
-    ADD_SERIALIZE_METHODS;
-
-    template <typename Stream, typename Operation>
-    inline void SerializationOp(Stream& s, Operation ser_action) {
-        READWRITEAS(CDiskBlockPos, *this);
-        READWRITE(VARINT(nTxOffset));
-    }
-
-    CDiskTxPos(const CDiskBlockPos &blockIn, unsigned int nTxOffsetIn) : CDiskBlockPos(blockIn.nFile, blockIn.nPos), nTxOffset(nTxOffsetIn) {
-    }
-
-    CDiskTxPos() {
-        SetNull();
-    }
-
-    void SetNull() {
-        CDiskBlockPos::SetNull();
-        nTxOffset = 0;
-    }
-};
-
 /** CCoinsView backed by the coin database (chainstate/) */
 class CCoinsViewDB final : public CCoinsView
 {
@@ -123,43 +98,4 @@ public:
     bool LoadBlockIndexGuts(const Consensus::Params& consensusParams, std::function<CBlockIndex*(const uint256&)> insertBlockIndex);
 };
 
-class BaseIndexDB : public CDBWrapper
-{
-public:
-    BaseIndexDB(const fs::path& path, size_t n_cache_size,
-                bool f_memory = false, bool f_wipe = false, bool f_obfuscate = false);
-
-    /// Read block locator of the chain that the index is in sync with.
-    bool ReadBestBlock(CBlockLocator& locator) const;
-
-    /// Write block locator of the chain that the index is in sync with.
-    bool WriteBestBlock(const CBlockLocator& locator);
-};
-
-/**
- * Access to the txindex database (indexes/txindex/)
- *
- * The database stores a block locator of the chain the database is synced to
- * so that the TxIndex can efficiently determine the point it last stopped at.
- * A locator is used instead of a simple hash of the chain tip because blocks
- * and block index entries may not be flushed to disk until after this database
- * is updated.
- */
-class TxIndexDB : public BaseIndexDB
-{
-public:
-    explicit TxIndexDB(size_t n_cache_size, bool f_memory = false, bool f_wipe = false);
-
-    /// Read the disk location of the transaction data with the given hash. Returns false if the
-    /// transaction hash is not indexed.
-    bool ReadTxPos(const uint256& txid, CDiskTxPos& pos) const;
-
-    /// Write a batch of transaction positions to the DB.
-    bool WriteTxs(const std::vector<std::pair<uint256, CDiskTxPos>>& v_pos);
-
-    /// 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