Merge bitcoin/bitcoin#33042: refactor: inline constant return values from dbwrapper write methods

743abbc refactor: inline constant return value of `BlockTreeDB::WriteBatchSync` and `BlockManager::WriteBlockIndexDB` and `BlockTreeDB::WriteFlag` (Lőrinc)
e030240 refactor: inline constant return value of `CDBWrapper::Erase` and `BlockTreeDB::WriteReindexing` (Lőrinc)
cdab948 refactor: inline constant return value of `CDBWrapper::Write` (Lőrinc)
d1847cf refactor: inline constant return value of `TxIndex::DB::WriteTxs` (Lőrinc)
50b63a5 refactor: inline constant return value of `CDBWrapper::WriteBatch` (Lőrinc)

Pull request description:

  Related to bitcoin/bitcoin#31144 (comment)

  ### Summary
  `WriteBatch` always returns `true` - the errors are handled by throwing `dbwrapper_error` instead.

  ### Context
  This boolean return value of the `Write` methods is confusing because it's inconsistent with `CDBWrapper::Read`, which catches exceptions and returns a boolean to indicate success/failure. It's bad that `Read` returns and `Write` throws - but it's a lot worse that `Write` advertises a return value when it actually communicates errors through exceptions.

  ### Solution
  This PR removes the constant return values from write methods and inlines `true` at their call sites. Many upstream methods had boolean return values only because they were propagating these constants - those have been cleaned up as well.

  Methods that returned a constant `true` value that now return `void`:
  - `CDBWrapper::WriteBatch`, `CDBWrapper::Write`, `CDBWrapper::Erase`
  - `TxIndex::DB::WriteTxs`
  - `BlockTreeDB::WriteReindexing`, `BlockTreeDB::WriteBatchSync`, `BlockTreeDB::WriteFlag`
  - `BlockManager::WriteBlockIndexDB`

  ### Note
  `CCoinsView::BatchWrite` (and transitively `CCoinsViewCache::Flush` & `CCoinsViewCache::Sync`) were intentionally not changed here. While all implementations return `true`, the base `CCoinsView::BatchWrite` returns `false`. Changing this would cause `coins_view` tests to fail with:
  > terminating due to uncaught exception of type std::logic_error: Not all unspent flagged entries were cleared

  We can fix that in a follow-up PR.

ACKs for top commit:
  achow101:
    ACK 743abbc
  janb84:
    ACK 743abbc
  TheCharlatan:
    ACK 743abbc
  sipa:
    ACK 743abbc

Tree-SHA512: b2a550bff066216f1958d2dd9a7ef6a9949de518cc636f8ab9c670e0b7a330c1eb8c838e458a8629acb8ac980cea6616955cd84436a7b8ab9096f6d648073b1e

Author: achow101

src/dbwrapper.cpp

@@ -274,7 +274,7 @@ CDBWrapper::~CDBWrapper()
     DBContext().options.env = nullptr;
 }
 
-bool CDBWrapper::WriteBatch(CDBBatch& batch, bool fSync)
+void CDBWrapper::WriteBatch(CDBBatch& batch, bool fSync)
 {
     const bool log_memory = LogAcceptCategory(BCLog::LEVELDB, BCLog::Level::Debug);
     double mem_before = 0;
@@ -288,7 +288,6 @@ bool CDBWrapper::WriteBatch(CDBBatch& batch, bool fSync)
         LogDebug(BCLog::LEVELDB, "WriteBatch memory usage: db=%s, before=%.1fMiB, after=%.1fMiB\n",
                  m_name, mem_before, mem_after);
     }
-    return true;
 }
 
 size_t CDBWrapper::DynamicMemoryUsage() const

src/dbwrapper.h

@@ -230,11 +230,11 @@ class CDBWrapper
     }
 
     template <typename K, typename V>
-    bool Write(const K& key, const V& value, bool fSync = false)
+    void Write(const K& key, const V& value, bool fSync = false)
     {
         CDBBatch batch(*this);
         batch.Write(key, value);
-        return WriteBatch(batch, fSync);
+        WriteBatch(batch, fSync);
     }
 
     //! @returns filesystem path to the on-disk data.
@@ -255,14 +255,14 @@ class CDBWrapper
     }
 
     template <typename K>
-    bool Erase(const K& key, bool fSync = false)
+    void Erase(const K& key, bool fSync = false)
     {
         CDBBatch batch(*this);
         batch.Erase(key);
-        return WriteBatch(batch, fSync);
+        WriteBatch(batch, fSync);
     }
 
-    bool WriteBatch(CDBBatch& batch, bool fSync = false);
+    void WriteBatch(CDBBatch& batch, bool fSync = false);
 
     // Get an estimate of LevelDB memory usage (in bytes).
     size_t DynamicMemoryUsage() const;

src/index/base.cpp

@@ -275,7 +275,7 @@ bool BaseIndex::Commit()
         ok = CustomCommit(batch);
         if (ok) {
             GetDB().WriteBestBlock(batch, GetLocator(*m_chain, m_best_block_index.load()->GetBlockHash()));
-            ok = GetDB().WriteBatch(batch);
+            GetDB().WriteBatch(batch);
         }
     }
     if (!ok) {

src/index/blockfilterindex.cpp

@@ -311,9 +311,7 @@ bool BlockFilterIndex::Write(const BlockFilter& filter, uint32_t block_height, c
     value.second.header = filter_header;
     value.second.pos = m_next_filter_pos;
 
-    if (!m_db->Write(DBHeightKey(block_height), value)) {
-        return false;
-    }
+    m_db->Write(DBHeightKey(block_height), value);
 
     m_next_filter_pos.nPos += bytes_written;
     return true;
@@ -358,7 +356,7 @@ bool BlockFilterIndex::CustomRemove(const interfaces::BlockInfo& block)
     // But since this creates new references to the filter, the position should get updated here
     // atomically as well in case Commit fails.
     batch.Write(DB_FILTER_POS, m_next_filter_pos);
-    if (!m_db->WriteBatch(batch)) return false;
+    m_db->WriteBatch(batch);
 
     // Update cached header to the previous block hash
     m_last_header = *Assert(ReadFilterHeader(block.height - 1, *Assert(block.prev_hash)));

src/index/coinstatsindex.cpp

@@ -253,7 +253,8 @@ bool CoinStatsIndex::CustomAppend(const interfaces::BlockInfo& block)
 
     // Intentionally do not update DB_MUHASH here so it stays in sync with
     // DB_BEST_BLOCK, and the index is not corrupted if there is an unclean shutdown.
-    return m_db->Write(DBHeightKey(block.height), value);
+    m_db->Write(DBHeightKey(block.height), value);
+    return true;
 }
 
 [[nodiscard]] static bool CopyHeightIndexToHashIndex(CDBIterator& db_it, CDBBatch& batch,
@@ -290,7 +291,7 @@ bool CoinStatsIndex::CustomRemove(const interfaces::BlockInfo& block)
         return false;
     }
 
-    if (!m_db->WriteBatch(batch)) return false;
+    m_db->WriteBatch(batch);
 
     if (!RevertBlock(block)) {
         return false; // failure cause logged internally

src/index/txindex.cpp

@@ -46,7 +46,7 @@ class TxIndex::DB : public BaseIndex::DB
     bool ReadTxPos(const Txid& txid, CDiskTxPos& pos) const;
 
     /// Write a batch of transaction positions to the DB.
-    [[nodiscard]] bool WriteTxs(const std::vector<std::pair<Txid, CDiskTxPos>>& v_pos);
+    void WriteTxs(const std::vector<std::pair<Txid, CDiskTxPos>>& v_pos);
 };
 
 TxIndex::DB::DB(size_t n_cache_size, bool f_memory, bool f_wipe) :
@@ -58,13 +58,13 @@ bool TxIndex::DB::ReadTxPos(const Txid& txid, CDiskTxPos& pos) const
     return Read(std::make_pair(DB_TXINDEX, txid.ToUint256()), pos);
 }
 
-bool TxIndex::DB::WriteTxs(const std::vector<std::pair<Txid, CDiskTxPos>>& v_pos)
+void TxIndex::DB::WriteTxs(const std::vector<std::pair<Txid, CDiskTxPos>>& v_pos)
 {
     CDBBatch batch(*this);
     for (const auto& [txid, pos] : v_pos) {
         batch.Write(std::make_pair(DB_TXINDEX, txid.ToUint256()), pos);
     }
-    return WriteBatch(batch);
+    WriteBatch(batch);
 }
 
 TxIndex::TxIndex(std::unique_ptr<interfaces::Chain> chain, size_t n_cache_size, bool f_memory, bool f_wipe)
@@ -86,7 +86,8 @@ bool TxIndex::CustomAppend(const interfaces::BlockInfo& block)
         vPos.emplace_back(tx->GetHash(), pos);
         pos.nTxOffset += ::GetSerializeSize(TX_WITH_WITNESS(*tx));
     }
-    return m_db->WriteTxs(vPos);
+    m_db->WriteTxs(vPos);
+    return true;
 }
 
 BaseIndex::DB& TxIndex::GetDB() const { return *m_db; }

src/node/blockstorage.cpp

@@ -59,12 +59,12 @@ bool BlockTreeDB::ReadBlockFileInfo(int nFile, CBlockFileInfo& info)
     return Read(std::make_pair(DB_BLOCK_FILES, nFile), info);
 }
 
-bool BlockTreeDB::WriteReindexing(bool fReindexing)
+void BlockTreeDB::WriteReindexing(bool fReindexing)
 {
     if (fReindexing) {
-        return Write(DB_REINDEX_FLAG, uint8_t{'1'});
+        Write(DB_REINDEX_FLAG, uint8_t{'1'});
     } else {
-        return Erase(DB_REINDEX_FLAG);
+        Erase(DB_REINDEX_FLAG);
     }
 }
 
@@ -78,7 +78,7 @@ bool BlockTreeDB::ReadLastBlockFile(int& nFile)
     return Read(DB_LAST_BLOCK, nFile);
 }
 
-bool BlockTreeDB::WriteBatchSync(const std::vector<std::pair<int, const CBlockFileInfo*>>& fileInfo, int nLastFile, const std::vector<const CBlockIndex*>& blockinfo)
+void BlockTreeDB::WriteBatchSync(const std::vector<std::pair<int, const CBlockFileInfo*>>& fileInfo, int nLastFile, const std::vector<const CBlockIndex*>& blockinfo)
 {
     CDBBatch batch(*this);
     for (const auto& [file, info] : fileInfo) {
@@ -88,12 +88,12 @@ bool BlockTreeDB::WriteBatchSync(const std::vector<std::pair<int, const CBlockFi
     for (const CBlockIndex* bi : blockinfo) {
         batch.Write(std::make_pair(DB_BLOCK_INDEX, bi->GetBlockHash()), CDiskBlockIndex{bi});
     }
-    return WriteBatch(batch, true);
+    WriteBatch(batch, true);
 }
 
-bool BlockTreeDB::WriteFlag(const std::string& name, bool fValue)
+void BlockTreeDB::WriteFlag(const std::string& name, bool fValue)
 {
-    return Write(std::make_pair(DB_FLAG, name), fValue ? uint8_t{'1'} : uint8_t{'0'});
+    Write(std::make_pair(DB_FLAG, name), fValue ? uint8_t{'1'} : uint8_t{'0'});
 }
 
 bool BlockTreeDB::ReadFlag(const std::string& name, bool& fValue)
@@ -477,7 +477,7 @@ bool BlockManager::LoadBlockIndex(const std::optional<uint256>& snapshot_blockha
     return true;
 }
 
-bool BlockManager::WriteBlockIndexDB()
+void BlockManager::WriteBlockIndexDB()
 {
     AssertLockHeld(::cs_main);
     std::vector<std::pair<int, const CBlockFileInfo*>> vFiles;
@@ -493,10 +493,7 @@ bool BlockManager::WriteBlockIndexDB()
         m_dirty_blockindex.erase(it++);
     }
     int max_blockfile = WITH_LOCK(cs_LastBlockFile, return this->MaxBlockfileNum());
-    if (!m_block_tree_db->WriteBatchSync(vFiles, max_blockfile, vBlocks)) {
-        return false;
-    }
-    return true;
+    m_block_tree_db->WriteBatchSync(vFiles, max_blockfile, vBlocks);
 }
 
 bool BlockManager::LoadBlockIndexDB(const std::optional<uint256>& snapshot_blockhash)

src/node/blockstorage.h

@@ -52,12 +52,12 @@ class BlockTreeDB : public CDBWrapper
 {
 public:
     using CDBWrapper::CDBWrapper;
-    bool WriteBatchSync(const std::vector<std::pair<int, const CBlockFileInfo*>>& fileInfo, int nLastFile, const std::vector<const CBlockIndex*>& blockinfo);
+    void WriteBatchSync(const std::vector<std::pair<int, const CBlockFileInfo*>>& fileInfo, int nLastFile, const std::vector<const CBlockIndex*>& blockinfo);
     bool ReadBlockFileInfo(int nFile, CBlockFileInfo& info);
     bool ReadLastBlockFile(int& nFile);
-    bool WriteReindexing(bool fReindexing);
+    void WriteReindexing(bool fReindexing);
     void ReadReindexing(bool& fReindexing);
-    bool WriteFlag(const std::string& name, bool fValue);
+    void WriteFlag(const std::string& name, bool fValue);
     bool ReadFlag(const std::string& name, bool& fValue);
     bool LoadBlockIndexGuts(const Consensus::Params& consensusParams, std::function<CBlockIndex*(const uint256&)> insertBlockIndex, const util::SignalInterrupt& interrupt)
         EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
@@ -300,7 +300,7 @@ class BlockManager
 
     std::unique_ptr<BlockTreeDB> m_block_tree_db GUARDED_BY(::cs_main);
 
-    bool WriteBlockIndexDB() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
+    void WriteBlockIndexDB() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
     bool LoadBlockIndexDB(const std::optional<uint256>& snapshot_blockhash)
         EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
 

src/test/dbwrapper_tests.cpp

@@ -39,7 +39,7 @@ BOOST_AUTO_TEST_CASE(dbwrapper)
             for (uint8_t k{0}; k < 10; ++k) {
                 uint8_t key{k};
                 uint256 value{m_rng.rand256()};
-                BOOST_CHECK(dbw.Write(key, value));
+                dbw.Write(key, value);
                 key_values.emplace_back(key, value);
             }
         }
@@ -86,52 +86,52 @@ BOOST_AUTO_TEST_CASE(dbwrapper_basic_data)
         std::string key_block = "b" + m_rng.rand256().ToString();
 
         uint256 in_block = m_rng.rand256();
-        BOOST_CHECK(dbw.Write(key_block, in_block));
+        dbw.Write(key_block, in_block);
         BOOST_CHECK(dbw.Read(key_block, res));
         BOOST_CHECK_EQUAL(res.ToString(), in_block.ToString());
 
         //Simulate file raw data - "f + file_number"
         std::string key_file = strprintf("f%04x", m_rng.rand32());
 
         uint256 in_file_info = m_rng.rand256();
-        BOOST_CHECK(dbw.Write(key_file, in_file_info));
+        dbw.Write(key_file, in_file_info);
         BOOST_CHECK(dbw.Read(key_file, res));
         BOOST_CHECK_EQUAL(res.ToString(), in_file_info.ToString());
 
         //Simulate transaction raw data - "t + transaction hash"
         std::string key_transaction = "t" + m_rng.rand256().ToString();
 
         uint256 in_transaction = m_rng.rand256();
-        BOOST_CHECK(dbw.Write(key_transaction, in_transaction));
+        dbw.Write(key_transaction, in_transaction);
         BOOST_CHECK(dbw.Read(key_transaction, res));
         BOOST_CHECK_EQUAL(res.ToString(), in_transaction.ToString());
 
         //Simulate UTXO raw data - "c + transaction hash"
         std::string key_utxo = "c" + m_rng.rand256().ToString();
 
         uint256 in_utxo = m_rng.rand256();
-        BOOST_CHECK(dbw.Write(key_utxo, in_utxo));
+        dbw.Write(key_utxo, in_utxo);
         BOOST_CHECK(dbw.Read(key_utxo, res));
         BOOST_CHECK_EQUAL(res.ToString(), in_utxo.ToString());
 
         //Simulate last block file number - "l"
         uint8_t key_last_blockfile_number{'l'};
         uint32_t lastblockfilenumber = m_rng.rand32();
-        BOOST_CHECK(dbw.Write(key_last_blockfile_number, lastblockfilenumber));
+        dbw.Write(key_last_blockfile_number, lastblockfilenumber);
         BOOST_CHECK(dbw.Read(key_last_blockfile_number, res_uint_32));
         BOOST_CHECK_EQUAL(lastblockfilenumber, res_uint_32);
 
         //Simulate Is Reindexing - "R"
         uint8_t key_IsReindexing{'R'};
         bool isInReindexing = m_rng.randbool();
-        BOOST_CHECK(dbw.Write(key_IsReindexing, isInReindexing));
+        dbw.Write(key_IsReindexing, isInReindexing);
         BOOST_CHECK(dbw.Read(key_IsReindexing, res_bool));
         BOOST_CHECK_EQUAL(isInReindexing, res_bool);
 
         //Simulate last block hash up to which UXTO covers - 'B'
         uint8_t key_lastblockhash_uxto{'B'};
         uint256 lastblock_hash = m_rng.rand256();
-        BOOST_CHECK(dbw.Write(key_lastblockhash_uxto, lastblock_hash));
+        dbw.Write(key_lastblockhash_uxto, lastblock_hash);
         BOOST_CHECK(dbw.Read(key_lastblockhash_uxto, res));
         BOOST_CHECK_EQUAL(lastblock_hash, res);
 
@@ -142,7 +142,7 @@ BOOST_AUTO_TEST_CASE(dbwrapper_basic_data)
         std::string key_file_option = strprintf("%s%01x%s", file_option_tag, filename_length, filename);
 
         bool in_file_bool = m_rng.randbool();
-        BOOST_CHECK(dbw.Write(key_file_option, in_file_bool));
+        dbw.Write(key_file_option, in_file_bool);
         BOOST_CHECK(dbw.Read(key_file_option, res_bool));
         BOOST_CHECK_EQUAL(res_bool, in_file_bool);
     }
@@ -173,7 +173,7 @@ BOOST_AUTO_TEST_CASE(dbwrapper_batch)
         // Remove key3 before it's even been written
         batch.Erase(key3);
 
-        BOOST_CHECK(dbw.WriteBatch(batch));
+        dbw.WriteBatch(batch);
 
         BOOST_CHECK(dbw.Read(key, res));
         BOOST_CHECK_EQUAL(res.ToString(), in.ToString());
@@ -195,10 +195,10 @@ BOOST_AUTO_TEST_CASE(dbwrapper_iterator)
         // The two keys are intentionally chosen for ordering
         uint8_t key{'j'};
         uint256 in = m_rng.rand256();
-        BOOST_CHECK(dbw.Write(key, in));
+        dbw.Write(key, in);
         uint8_t key2{'k'};
         uint256 in2 = m_rng.rand256();
-        BOOST_CHECK(dbw.Write(key2, in2));
+        dbw.Write(key2, in2);
 
         std::unique_ptr<CDBIterator> it(const_cast<CDBWrapper&>(dbw).NewIterator());
 
@@ -238,7 +238,7 @@ BOOST_AUTO_TEST_CASE(existing_data_no_obfuscate)
     uint256 in = m_rng.rand256();
     uint256 res;
 
-    BOOST_CHECK(dbw->Write(key, in));
+    dbw->Write(key, in);
     BOOST_CHECK(dbw->Read(key, res));
     BOOST_CHECK_EQUAL(res.ToString(), in.ToString());
 
@@ -261,7 +261,7 @@ BOOST_AUTO_TEST_CASE(existing_data_no_obfuscate)
     uint256 res3;
 
     // Check that we can write successfully
-    BOOST_CHECK(odbw.Write(key, in2));
+    odbw.Write(key, in2);
     BOOST_CHECK(odbw.Read(key, res3));
     BOOST_CHECK_EQUAL(res3.ToString(), in2.ToString());
 }
@@ -279,7 +279,7 @@ BOOST_AUTO_TEST_CASE(existing_data_reindex)
     uint256 in = m_rng.rand256();
     uint256 res;
 
-    BOOST_CHECK(dbw->Write(key, in));
+    dbw->Write(key, in);
     BOOST_CHECK(dbw->Read(key, res));
     BOOST_CHECK_EQUAL(res.ToString(), in.ToString());
 
@@ -298,7 +298,7 @@ BOOST_AUTO_TEST_CASE(existing_data_reindex)
     uint256 res3;
 
     // Check that we can write successfully
-    BOOST_CHECK(odbw.Write(key, in2));
+    odbw.Write(key, in2);
     BOOST_CHECK(odbw.Read(key, res3));
     BOOST_CHECK_EQUAL(res3.ToString(), in2.ToString());
 }
@@ -310,7 +310,7 @@ BOOST_AUTO_TEST_CASE(iterator_ordering)
     for (int x=0x00; x<256; ++x) {
         uint8_t key = x;
         uint32_t value = x*x;
-        if (!(x & 1)) BOOST_CHECK(dbw.Write(key, value));
+        if (!(x & 1)) dbw.Write(key, value);
     }
 
     // Check that creating an iterator creates a snapshot
@@ -319,7 +319,7 @@ BOOST_AUTO_TEST_CASE(iterator_ordering)
     for (unsigned int x=0x00; x<256; ++x) {
         uint8_t key = x;
         uint32_t value = x*x;
-        if (x & 1) BOOST_CHECK(dbw.Write(key, value));
+        if (x & 1) dbw.Write(key, value);
     }
 
     for (const int seek_start : {0x00, 0x80}) {
@@ -381,7 +381,7 @@ BOOST_AUTO_TEST_CASE(iterator_string_ordering)
             for (int z = 0; z < y; ++z)
                 key += key;
             uint32_t value = x*x;
-            BOOST_CHECK(dbw.Write(StringContentsSerializer{key}, value));
+            dbw.Write(StringContentsSerializer{key}, value);
         }
     }
 

src/test/fuzz/block_index.cpp

@@ -89,7 +89,7 @@ FUZZ_TARGET(block_index, .init = init_block_index)
     }
 
     // Store these files and blocks in the block index. It should not fail.
-    assert(block_index.WriteBatchSync(files_info, files_count - 1, blocks_info));
+    block_index.WriteBatchSync(files_info, files_count - 1, blocks_info);
 
     // We should be able to read every block file info we stored. Its value should correspond to
     // what we stored above.