Merge bitcoin/bitcoin#24410: [kernel 2a/n] Split hashing/index `GetUTXOStats` codepaths, decouple from `coinstatsindex`

664a14ba7ccb40aa82d35a59831acd35db1897a6 coinstats: Move GetUTXOStats to rpc/blockchain (Carl Dong)
f1006875665ffe8ff5da8185effe25b860743b4e kernel: Use ComputeUTXOStats in validation (Carl Dong)
faa52387e8e4856445b1cfc9b5e072ce8f690f36 style-only: Rearrange using decls after scripted-diff (Carl Dong)
f329a9298c06ffe74b9e9fbc07bfe6d282fef9cb scripted-diff: Move src/kernel/coinstats to kernel:: (Carl Dong)
0e54456f0498e52131f8ae0c76b4dfe25f45b076 Use only kernel/coinstats.h in index/coinstatsindex.h (Carl Dong)
80970985c965f79b8c376c8a922497e385445dd8 coinstats: Split node/coinstats.h to kernel/coinstats.h (Carl Dong)
35f73ce4b2efd7341fe55f77b334f27ad8aad090 coinstats: Move hasher codepath to kernel/coinstats (Carl Dong)
b7634fe02b6b030f5d62502c73db84ba9a276640 Move logic from LookupUTXOStatsWithIndex to CoinStatsIndex::LookUpStats (Carl Dong)
1352e410a5b84070279ff28399083cb3ab278593 coinstats: Separate hasher/index lookup codepaths (Carl Dong)
524463daf6a10b20a4e20116a68101a684929eda coinstats: Return purely out-param CCoinsStats (Carl Dong)
46eb9fc56a296a2acea10ec7e5bf7b1827f73c45 coinstats: Extract index_requested in-member to in-param (Carl Dong)
a789f3f2b878e1236f8e043a8bb1ffb1afc1b673 coinstats: Extract hash_type in-member to in-param (Carl Dong)
102294898d708b7adc0150aba8e500a4aa19bc1c includes: Remove rpc/util.h -> node/coinstats.h (Carl Dong)
0848db9c35d9eae4d68cbdbef68c337656f3c906 fuzz: Remove useless GetUTXOStats fuzz case (Carl Dong)
52b1939993771d0a8a718ca1667241872de8241a kernel: Remove unnecessary blockfilter{index,}.cpp (Carl Dong)

Pull request description:

  Part of: #24303
  Depends on: #24322

  The `GetUTXOStats` function has 2 codepaths:
    - One which queries the `CoinStatsIndex` for the UTXO hash
    - One which actually performs the hashing

  For `libbitcoinkernel`, the only place where we call `GetUTXOStats` is in `PopulateAndValidateSnapshots`, which uses the `SHA256D` hash, and is therefore unable to use the `CoinStatsIndex` since that only provides `MuHash` hashes. Not that I think indices necessarily belong in `libbitcoinkernel` anyway.

  This PR separates these 2 aforementioned codepaths of `GetUTXOStats`, uses the hashing codepath in `PopulateAndValidateSnapshots`, and removes the need to link in `index/coinstatsindex.cpp` and `node/coinstats.cpp`.

  -----

  Logistically, this PR:
  - Extracts out the `index_requested` and `hash_type` members of `CoinStats`, which served as "in-params" to `GetUTXOStats` embedded within the `CoinStats` struct. This allows `CoinStats` to only consist of "out-param" members, and be returned by `GetUTXOStats` without needing to be an "in-out" param
  - Introduce the purely virtual `UTXOHashers` class, with 3 implementations: `SHA256DHasher`, `MuHashHasher`, and `NullHasher`. These replace the existing template-based polymorphism.
  - Split `GetUTXOStats` into:
      - `CalculateUTXOStatsWithHasher(UTXOHasher&, ...)`, and
      - `LookupUTXOStatsWithIndex(CoinStatsIndex&, ...)`
  - Use `CalculateUTXOStatsWithHasher` directly where appropriate (`src/validation.cpp` and `src/fuzz`)
  - Move `GetUTXOStats` to `rpc/blockchain`, which is the only place that depends on `GetUTXOStats`'s weird fallback behaviour
  - Move `LookupUTXOStatsWithIndex` to `index/coinstatsindex`

  Code organization:
  - `src/`
    - `kernel/` → only contains the hashing codepath
      - `coinstats.cpp` → hashing codepath implementations
      - `coinstats.h` → header for `kernel/coinstats.cpp`
    - `index/` → only contains the index codepath
      - `coinstatsindex.cpp` → index codepath implementations
      - `coinstatsindex.h`
    - `validation.cpp` → only uses the hashing codepath
    - `rpc/blockchain.cpp` → uses both the hashing and index codepath, old `GetUTXOStats` fallback logic moved here as static
    - `test/fuzz/coins_view.cpp` → only uses the hashing codepath

  TODOs:
  - [x] Commit messages could be fleshed out more

  Would love any feedback!

ACKs for top commit:
  laanwj:
    Code review ACK 664a14ba7ccb40aa82d35a59831acd35db1897a6

Tree-SHA512: 18722c7bd279174d2d1881fec33ea04a9b261aae1c12e998cf434ef297d8ded47de69c526c8033a2ba7abc93ba3d2ff5faf4ce05e8888c725c31cf885ce3ef73

10 files changed, 145 insertions, 130 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index a0e793e42a..7f82d188f0 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -172,6 +172,7 @@ BITCOIN_CORE_H = \
   interfaces/node.h \
   interfaces/wallet.h \
   kernel/chainstatemanager_opts.h \
+  kernel/coinstats.h \
   key.h \
   key_io.h \
   logging.h \
@@ -191,7 +192,6 @@ BITCOIN_CORE_H = \
   node/caches.h \
   node/chainstate.h \
   node/coin.h \
-  node/coinstats.h \
   node/context.h \
   node/miner.h \
   node/minisketchwrapper.h \
@@ -357,6 +357,7 @@ libbitcoin_node_a_SOURCES = \
   index/coinstatsindex.cpp \
   index/txindex.cpp \
   init.cpp \
+  kernel/coinstats.cpp \
   mapport.cpp \
   net.cpp \
   netgroup.cpp \
@@ -365,7 +366,6 @@ libbitcoin_node_a_SOURCES = \
   node/caches.cpp \
   node/chainstate.cpp \
   node/coin.cpp \
-  node/coinstats.cpp \
   node/context.cpp \
   node/interfaces.cpp \
   node/miner.cpp \
@@ -853,7 +853,6 @@ endif
 libbitcoinkernel_la_SOURCES = \
   kernel/bitcoinkernel.cpp \
   arith_uint256.cpp \
-  blockfilter.cpp \
   chain.cpp \
   chainparamsbase.cpp \
   chainparams.cpp \
@@ -871,15 +870,12 @@ libbitcoinkernel_la_SOURCES = \
   flatfile.cpp \
   fs.cpp \
   hash.cpp \
-  index/base.cpp \
-  index/blockfilterindex.cpp \
-  index/coinstatsindex.cpp \
   init/common.cpp \
+  kernel/coinstats.cpp \
   key.cpp \
   logging.cpp \
   node/blockstorage.cpp \
   node/chainstate.cpp \
-  node/coinstats.cpp \
   node/ui_interface.cpp \
   policy/feerate.cpp \
   policy/fees.cpp \
diff --git a/src/index/coinstatsindex.cpp b/src/index/coinstatsindex.cpp
index 69078708f9..687e330fe0 100644
--- a/src/index/coinstatsindex.cpp
+++ b/src/index/coinstatsindex.cpp
@@ -12,10 +12,11 @@
 #include <undo.h>
 #include <validation.h>
 
-using node::CCoinsStats;
-using node::GetBogoSize;
+using kernel::CCoinsStats;
+using kernel::GetBogoSize;
+using kernel::TxOutSer;
+
 using node::ReadBlockFromDisk;
-using node::TxOutSer;
 using node::UndoReadFromDisk;
 
 static constexpr uint8_t DB_BLOCK_HASH{'s'};
@@ -316,28 +317,31 @@ static bool LookUpOne(const CDBWrapper& db, const CBlockIndex* block_index, DBVa
     return db.Read(DBHashKey(block_index->GetBlockHash()), result);
 }
 
-bool CoinStatsIndex::LookUpStats(const CBlockIndex* block_index, CCoinsStats& coins_stats) const
+std::optional<CCoinsStats> CoinStatsIndex::LookUpStats(const CBlockIndex* block_index) const
 {
+    CCoinsStats stats{Assert(block_index)->nHeight, block_index->GetBlockHash()};
+    stats.index_used = true;
+
     DBVal entry;
     if (!LookUpOne(*m_db, block_index, entry)) {
-        return false;
+        return std::nullopt;
     }
 
-    coins_stats.hashSerialized = entry.muhash;
-    coins_stats.nTransactionOutputs = entry.transaction_output_count;
-    coins_stats.nBogoSize = entry.bogo_size;
-    coins_stats.total_amount = entry.total_amount;
-    coins_stats.total_subsidy = entry.total_subsidy;
-    coins_stats.total_unspendable_amount = entry.total_unspendable_amount;
-    coins_stats.total_prevout_spent_amount = entry.total_prevout_spent_amount;
-    coins_stats.total_new_outputs_ex_coinbase_amount = entry.total_new_outputs_ex_coinbase_amount;
-    coins_stats.total_coinbase_amount = entry.total_coinbase_amount;
-    coins_stats.total_unspendables_genesis_block = entry.total_unspendables_genesis_block;
-    coins_stats.total_unspendables_bip30 = entry.total_unspendables_bip30;
-    coins_stats.total_unspendables_scripts = entry.total_unspendables_scripts;
-    coins_stats.total_unspendables_unclaimed_rewards = entry.total_unspendables_unclaimed_rewards;
-
-    return true;
+    stats.hashSerialized = entry.muhash;
+    stats.nTransactionOutputs = entry.transaction_output_count;
+    stats.nBogoSize = entry.bogo_size;
+    stats.total_amount = entry.total_amount;
+    stats.total_subsidy = entry.total_subsidy;
+    stats.total_unspendable_amount = entry.total_unspendable_amount;
+    stats.total_prevout_spent_amount = entry.total_prevout_spent_amount;
+    stats.total_new_outputs_ex_coinbase_amount = entry.total_new_outputs_ex_coinbase_amount;
+    stats.total_coinbase_amount = entry.total_coinbase_amount;
+    stats.total_unspendables_genesis_block = entry.total_unspendables_genesis_block;
+    stats.total_unspendables_bip30 = entry.total_unspendables_bip30;
+    stats.total_unspendables_scripts = entry.total_unspendables_scripts;
+    stats.total_unspendables_unclaimed_rewards = entry.total_unspendables_unclaimed_rewards;
+
+    return stats;
 }
 
 bool CoinStatsIndex::Init()
diff --git a/src/index/coinstatsindex.h b/src/index/coinstatsindex.h
index 6f53bb74fb..cae052d913 100644
--- a/src/index/coinstatsindex.h
+++ b/src/index/coinstatsindex.h
@@ -9,7 +9,7 @@
 #include <crypto/muhash.h>
 #include <flatfile.h>
 #include <index/base.h>
-#include <node/coinstats.h>
+#include <kernel/coinstats.h>
 
 /**
  * CoinStatsIndex maintains statistics on the UTXO set.
@@ -56,7 +56,7 @@ public:
     explicit CoinStatsIndex(size_t n_cache_size, bool f_memory = false, bool f_wipe = false);
 
     // Look up stats for a specific block using CBlockIndex
-    bool LookUpStats(const CBlockIndex* block_index, node::CCoinsStats& coins_stats) const;
+    std::optional<kernel::CCoinsStats> LookUpStats(const CBlockIndex* block_index) const;
 };
 
 /// The global UTXO set hash object.
diff --git a/src/node/coinstats.cpp b/src/kernel/coinstats.cpp
index eed43a1bc7..f380871627 100644
--- a/src/node/coinstats.cpp
+++ b/src/kernel/coinstats.cpp
@@ -1,14 +1,12 @@
-// Copyright (c) 2010 Satoshi Nakamoto
-// Copyright (c) 2009-2021 The Bitcoin Core developers
+// Copyright (c) 2022 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include <node/coinstats.h>
+#include <kernel/coinstats.h>
 
 #include <coins.h>
 #include <crypto/muhash.h>
 #include <hash.h>
-#include <index/coinstatsindex.h>
 #include <serialize.h>
 #include <uint256.h>
 #include <util/overflow.h>
@@ -17,7 +15,12 @@
 
 #include <map>
 
-namespace node {
+namespace kernel {
+
+CCoinsStats::CCoinsStats(int block_height, const uint256& block_hash)
+    : nHeight(block_height),
+      hashBlock(block_hash) {}
+
 // Database-independent metric indicating the UTXO set size
 uint64_t GetBogoSize(const CScript& script_pub_key)
 {
@@ -93,24 +96,11 @@ static void ApplyStats(CCoinsStats& stats, const uint256& hash, const std::map<u
 
 //! Calculate statistics about the unspent transaction output set
 template <typename T>
-static bool GetUTXOStats(CCoinsView* view, BlockManager& blockman, CCoinsStats& stats, T hash_obj, const std::function<void()>& interruption_point, const CBlockIndex* pindex)
+static bool ComputeUTXOStats(CCoinsView* view, CCoinsStats& stats, T hash_obj, const std::function<void()>& interruption_point)
 {
     std::unique_ptr<CCoinsViewCursor> pcursor(view->Cursor());
     assert(pcursor);
 
-    if (!pindex) {
-        LOCK(cs_main);
-        pindex = blockman.LookupBlockIndex(view->GetBestBlock());
-    }
-    stats.nHeight = Assert(pindex)->nHeight;
-    stats.hashBlock = pindex->GetBlockHash();
-
-    // Use CoinStatsIndex if it is requested and available and a hash_type of Muhash or None was requested
-    if ((stats.m_hash_type == CoinStatsHashType::MUHASH || stats.m_hash_type == CoinStatsHashType::NONE) && g_coin_stats_index && stats.index_requested) {
-        stats.index_used = true;
-        return g_coin_stats_index->LookUpStats(pindex, stats);
-    }
-
     PrepareHash(hash_obj, stats);
 
     uint256 prevkey;
@@ -141,25 +131,36 @@ static bool GetUTXOStats(CCoinsView* view, BlockManager& blockman, CCoinsStats&
     FinalizeHash(hash_obj, stats);
 
     stats.nDiskSize = view->EstimateSize();
+
     return true;
 }
 
-bool GetUTXOStats(CCoinsView* view, BlockManager& blockman, CCoinsStats& stats, const std::function<void()>& interruption_point, const CBlockIndex* pindex)
+std::optional<CCoinsStats> ComputeUTXOStats(CoinStatsHashType hash_type, CCoinsView* view, node::BlockManager& blockman, const std::function<void()>& interruption_point)
 {
-    switch (stats.m_hash_type) {
-    case(CoinStatsHashType::HASH_SERIALIZED): {
-        CHashWriter ss(SER_GETHASH, PROTOCOL_VERSION);
-        return GetUTXOStats(view, blockman, stats, ss, interruption_point, pindex);
-    }
-    case(CoinStatsHashType::MUHASH): {
-        MuHash3072 muhash;
-        return GetUTXOStats(view, blockman, stats, muhash, interruption_point, pindex);
-    }
-    case(CoinStatsHashType::NONE): {
-        return GetUTXOStats(view, blockman, stats, nullptr, interruption_point, pindex);
+    CBlockIndex* pindex = WITH_LOCK(::cs_main, return blockman.LookupBlockIndex(view->GetBestBlock()));
+    CCoinsStats stats{Assert(pindex)->nHeight, pindex->GetBlockHash()};
+
+    bool success = [&]() -> bool {
+        switch (hash_type) {
+        case(CoinStatsHashType::HASH_SERIALIZED): {
+            CHashWriter ss(SER_GETHASH, PROTOCOL_VERSION);
+            return ComputeUTXOStats(view, stats, ss, interruption_point);
+        }
+        case(CoinStatsHashType::MUHASH): {
+            MuHash3072 muhash;
+            return ComputeUTXOStats(view, stats, muhash, interruption_point);
+        }
+        case(CoinStatsHashType::NONE): {
+            return ComputeUTXOStats(view, stats, nullptr, interruption_point);
+        }
+        } // no default case, so the compiler can warn about missing cases
+        assert(false);
+    }();
+
+    if (!success) {
+        return std::nullopt;
     }
-    } // no default case, so the compiler can warn about missing cases
-    assert(false);
+    return stats;
 }
 
 // The legacy hash serializes the hashBlock
@@ -182,4 +183,5 @@ static void FinalizeHash(MuHash3072& muhash, CCoinsStats& stats)
     stats.hashSerialized = out;
 }
 static void FinalizeHash(std::nullptr_t, CCoinsStats& stats) {}
-} // namespace node
+
+} // namespace kernel
diff --git a/src/node/coinstats.h b/src/kernel/coinstats.h
index aa771b18b0..a15957233f 100644
--- a/src/node/coinstats.h
+++ b/src/kernel/coinstats.h
@@ -1,10 +1,9 @@
-// Copyright (c) 2010 Satoshi Nakamoto
-// Copyright (c) 2009-2021 The Bitcoin Core developers
+// Copyright (c) 2022 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#ifndef BITCOIN_NODE_COINSTATS_H
-#define BITCOIN_NODE_COINSTATS_H
+#ifndef BITCOIN_KERNEL_COINSTATS_H
+#define BITCOIN_KERNEL_COINSTATS_H
 
 #include <chain.h>
 #include <coins.h>
@@ -20,7 +19,7 @@ namespace node {
 class BlockManager;
 } // namespace node
 
-namespace node {
+namespace kernel {
 enum class CoinStatsHashType {
     HASH_SERIALIZED,
     MUHASH,
@@ -28,9 +27,6 @@ enum class CoinStatsHashType {
 };
 
 struct CCoinsStats {
-    //! Which hash type to use
-    const CoinStatsHashType m_hash_type;
-
     int nHeight{0};
     uint256 hashBlock{};
     uint64_t nTransactions{0};
@@ -44,8 +40,6 @@ struct CCoinsStats {
     //! The number of coins contained.
     uint64_t coins_count{0};
 
-    //! Signals if the coinstatsindex should be used (when available).
-    bool index_requested{true};
     //! Signals if the coinstatsindex was used to retrieve the statistics.
     bool index_used{false};
 
@@ -70,15 +64,15 @@ struct CCoinsStats {
     //! Total cumulative amount of coins lost due to unclaimed miner rewards up to and including this block
     CAmount total_unspendables_unclaimed_rewards{0};
 
-    CCoinsStats(CoinStatsHashType hash_type) : m_hash_type(hash_type) {}
+    CCoinsStats() = default;
+    CCoinsStats(int block_height, const uint256& block_hash);
 };
 
-//! Calculate statistics about the unspent transaction output set
-bool GetUTXOStats(CCoinsView* view, node::BlockManager& blockman, CCoinsStats& stats, const std::function<void()>& interruption_point = {}, const CBlockIndex* pindex = nullptr);
-
 uint64_t GetBogoSize(const CScript& script_pub_key);
 
 CDataStream TxOutSer(const COutPoint& outpoint, const Coin& coin);
-} // namespace node
 
-#endif // BITCOIN_NODE_COINSTATS_H
+std::optional<CCoinsStats> ComputeUTXOStats(CoinStatsHashType hash_type, CCoinsView* view, node::BlockManager& blockman, const std::function<void()>& interruption_point = {});
+} // namespace kernel
+
+#endif // BITCOIN_KERNEL_COINSTATS_H
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 0a9458c276..03354f39f6 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -19,11 +19,11 @@
 #include <hash.h>
 #include <index/blockfilterindex.h>
 #include <index/coinstatsindex.h>
+#include <kernel/coinstats.h>
 #include <logging/timer.h>
 #include <net.h>
 #include <net_processing.h>
 #include <node/blockstorage.h>
-#include <node/coinstats.h>
 #include <node/context.h>
 #include <node/utxo_snapshot.h>
 #include <primitives/transaction.h>
@@ -51,10 +51,10 @@
 #include <memory>
 #include <mutex>
 
+using kernel::CCoinsStats;
+using kernel::CoinStatsHashType;
+
 using node::BlockManager;
-using node::CCoinsStats;
-using node::CoinStatsHashType;
-using node::GetUTXOStats;
 using node::NodeContext;
 using node::ReadBlockFromDisk;
 using node::SnapshotMetadata;
@@ -808,6 +808,36 @@ CoinStatsHashType ParseHashType(const std::string& hash_type_input)
     }
 }
 
+/**
+ * Calculate statistics about the unspent transaction output set
+ *
+ * @param[in] index_requested Signals if the coinstatsindex should be used (when available).
+ */
+static std::optional<kernel::CCoinsStats> GetUTXOStats(CCoinsView* view, node::BlockManager& blockman,
+                                                       kernel::CoinStatsHashType hash_type,
+                                                       const std::function<void()>& interruption_point = {},
+                                                       const CBlockIndex* pindex = nullptr,
+                                                       bool index_requested = true)
+{
+    // Use CoinStatsIndex if it is requested and available and a hash_type of Muhash or None was requested
+    if ((hash_type == kernel::CoinStatsHashType::MUHASH || hash_type == kernel::CoinStatsHashType::NONE) && g_coin_stats_index && index_requested) {
+        if (pindex) {
+            return g_coin_stats_index->LookUpStats(pindex);
+        } else {
+            CBlockIndex* block_index = WITH_LOCK(::cs_main, return blockman.LookupBlockIndex(view->GetBestBlock()));
+            return g_coin_stats_index->LookUpStats(block_index);
+        }
+    }
+
+    // If the coinstats index isn't requested or is otherwise not usable, the
+    // pindex should either be null or equal to the view's best block. This is
+    // because without the coinstats index we can only get coinstats about the
+    // best block.
+    CHECK_NONFATAL(!pindex || pindex->GetBlockHash() == view->GetBestBlock());
+
+    return kernel::ComputeUTXOStats(hash_type, view, blockman, interruption_point);
+}
+
 static RPCHelpMan gettxoutsetinfo()
 {
     return RPCHelpMan{"gettxoutsetinfo",
@@ -862,8 +892,7 @@ static RPCHelpMan gettxoutsetinfo()
 
     const CBlockIndex* pindex{nullptr};
     const CoinStatsHashType hash_type{request.params[0].isNull() ? CoinStatsHashType::HASH_SERIALIZED : ParseHashType(request.params[0].get_str())};
-    CCoinsStats stats{hash_type};
-    stats.index_requested = request.params[2].isNull() || request.params[2].get_bool();
+    bool index_requested = request.params[2].isNull() || request.params[2].get_bool();
 
     NodeContext& node = EnsureAnyNodeContext(request.context);
     ChainstateManager& chainman = EnsureChainman(node);
@@ -884,14 +913,14 @@ static RPCHelpMan gettxoutsetinfo()
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Querying specific block heights requires coinstatsindex");
         }
 
-        if (stats.m_hash_type == CoinStatsHashType::HASH_SERIALIZED) {
+        if (hash_type == CoinStatsHashType::HASH_SERIALIZED) {
             throw JSONRPCError(RPC_INVALID_PARAMETER, "hash_serialized_2 hash type cannot be queried for a specific block");
         }
 
         pindex = ParseHashOrHeight(request.params[1], chainman);
     }
 
-    if (stats.index_requested && g_coin_stats_index) {
+    if (index_requested && g_coin_stats_index) {
         if (!g_coin_stats_index->BlockUntilSyncedToCurrentChain()) {
             const IndexSummary summary{g_coin_stats_index->GetSummary()};
 
@@ -903,7 +932,9 @@ static RPCHelpMan gettxoutsetinfo()
         }
     }
 
-    if (GetUTXOStats(coins_view, *blockman, stats, node.rpc_interruption_point, pindex)) {
+    const std::optional<CCoinsStats> maybe_stats = GetUTXOStats(coins_view, *blockman, hash_type, node.rpc_interruption_point, pindex, index_requested);
+    if (maybe_stats.has_value()) {
+        const CCoinsStats& stats = maybe_stats.value();
         ret.pushKV("height", (int64_t)stats.nHeight);
         ret.pushKV("bestblock", stats.hashBlock.GetHex());
         ret.pushKV("txouts", (int64_t)stats.nTransactionOutputs);
@@ -922,10 +953,13 @@ static RPCHelpMan gettxoutsetinfo()
         } else {
             ret.pushKV("total_unspendable_amount", ValueFromAmount(stats.total_unspendable_amount));
 
-            CCoinsStats prev_stats{hash_type};
-
+            CCoinsStats prev_stats{};
             if (pindex->nHeight > 0) {
-                GetUTXOStats(coins_view, *blockman, prev_stats, node.rpc_interruption_point, pindex->pprev);
+                const std::optional<CCoinsStats> maybe_prev_stats = GetUTXOStats(coins_view, *blockman, hash_type, node.rpc_interruption_point, pindex->pprev, index_requested);
+                if (!maybe_prev_stats) {
+                    throw JSONRPCError(RPC_INTERNAL_ERROR, "Unable to read UTXO set");
+                }
+                prev_stats = maybe_prev_stats.value();
             }
 
             UniValue block_info(UniValue::VOBJ);
@@ -2285,7 +2319,7 @@ UniValue CreateUTXOSnapshot(
     const fs::path& temppath)
 {
     std::unique_ptr<CCoinsViewCursor> pcursor;
-    CCoinsStats stats{CoinStatsHashType::HASH_SERIALIZED};
+    std::optional<CCoinsStats> maybe_stats;
     const CBlockIndex* tip;
 
     {
@@ -2305,19 +2339,20 @@ UniValue CreateUTXOSnapshot(
 
         chainstate.ForceFlushStateToDisk();
 
-        if (!GetUTXOStats(&chainstate.CoinsDB(), chainstate.m_blockman, stats, node.rpc_interruption_point)) {
+        maybe_stats = GetUTXOStats(&chainstate.CoinsDB(), chainstate.m_blockman, CoinStatsHashType::HASH_SERIALIZED, node.rpc_interruption_point);
+        if (!maybe_stats) {
             throw JSONRPCError(RPC_INTERNAL_ERROR, "Unable to read UTXO set");
         }
 
         pcursor = chainstate.CoinsDB().Cursor();
-        tip = CHECK_NONFATAL(chainstate.m_blockman.LookupBlockIndex(stats.hashBlock));
+        tip = CHECK_NONFATAL(chainstate.m_blockman.LookupBlockIndex(maybe_stats->hashBlock));
     }
 
     LOG_TIME_SECONDS(strprintf("writing UTXO snapshot at height %s (%s) to file %s (via %s)",
         tip->nHeight, tip->GetBlockHash().ToString(),
         fs::PathToString(path), fs::PathToString(temppath)));
 
-    SnapshotMetadata metadata{tip->GetBlockHash(), stats.coins_count, tip->nChainTx};
+    SnapshotMetadata metadata{tip->GetBlockHash(), maybe_stats->coins_count, tip->nChainTx};
 
     afile << metadata;
 
@@ -2339,11 +2374,11 @@ UniValue CreateUTXOSnapshot(
     afile.fclose();
 
     UniValue result(UniValue::VOBJ);
-    result.pushKV("coins_written", stats.coins_count);
+    result.pushKV("coins_written", maybe_stats->coins_count);
     result.pushKV("base_hash", tip->GetBlockHash().ToString());
     result.pushKV("base_height", tip->nHeight);
     result.pushKV("path", path.u8string());
-    result.pushKV("txoutset_hash", stats.hashSerialized.ToString());
+    result.pushKV("txoutset_hash", maybe_stats->hashSerialized.ToString());
     // Cast required because univalue doesn't have serialization specified for
     // `unsigned int`, nChainTx's type.
     result.pushKV("nchaintx", uint64_t{tip->nChainTx});
diff --git a/src/rpc/util.h b/src/rpc/util.h
index abbc4c66fe..e883dc008e 100644
--- a/src/rpc/util.h
+++ b/src/rpc/util.h
@@ -5,7 +5,6 @@
 #ifndef BITCOIN_RPC_UTIL_H
 #define BITCOIN_RPC_UTIL_H
 
-#include <node/coinstats.h>
 #include <node/transaction.h>
 #include <outputtype.h>
 #include <protocol.h>
diff --git a/src/test/coinstatsindex_tests.cpp b/src/test/coinstatsindex_tests.cpp
index 5b73481bc1..50eb479035 100644
--- a/src/test/coinstatsindex_tests.cpp
+++ b/src/test/coinstatsindex_tests.cpp
@@ -13,8 +13,8 @@
 
 #include <chrono>
 
-using node::CCoinsStats;
-using node::CoinStatsHashType;
+using kernel::CCoinsStats;
+using kernel::CoinStatsHashType;
 
 BOOST_AUTO_TEST_SUITE(coinstatsindex_tests)
 
@@ -33,7 +33,6 @@ BOOST_FIXTURE_TEST_CASE(coinstatsindex_initial_sync, TestChain100Setup)
 {
     CoinStatsIndex coin_stats_index{1 << 20, true};
 
-    CCoinsStats coin_stats{CoinStatsHashType::MUHASH};
     const CBlockIndex* block_index;
     {
         LOCK(cs_main);
@@ -41,7 +40,7 @@ BOOST_FIXTURE_TEST_CASE(coinstatsindex_initial_sync, TestChain100Setup)
     }
 
     // CoinStatsIndex should not be found before it is started.
-    BOOST_CHECK(!coin_stats_index.LookUpStats(block_index, coin_stats));
+    BOOST_CHECK(!coin_stats_index.LookUpStats(block_index));
 
     // BlockUntilSyncedToCurrentChain should return false before CoinStatsIndex
     // is started.
@@ -57,10 +56,10 @@ BOOST_FIXTURE_TEST_CASE(coinstatsindex_initial_sync, TestChain100Setup)
         LOCK(cs_main);
         genesis_block_index = m_node.chainman->ActiveChain().Genesis();
     }
-    BOOST_CHECK(coin_stats_index.LookUpStats(genesis_block_index, coin_stats));
+    BOOST_CHECK(coin_stats_index.LookUpStats(genesis_block_index));
 
     // Check that CoinStatsIndex updates with new blocks.
-    coin_stats_index.LookUpStats(block_index, coin_stats);
+    BOOST_CHECK(coin_stats_index.LookUpStats(block_index));
 
     const CScript script_pub_key{CScript() << ToByteVector(coinbaseKey.GetPubKey()) << OP_CHECKSIG};
     std::vector<CMutableTransaction> noTxns;
@@ -69,13 +68,12 @@ BOOST_FIXTURE_TEST_CASE(coinstatsindex_initial_sync, TestChain100Setup)
     // Let the CoinStatsIndex to catch up again.
     BOOST_CHECK(coin_stats_index.BlockUntilSyncedToCurrentChain());
 
-    CCoinsStats new_coin_stats{CoinStatsHashType::MUHASH};
     const CBlockIndex* new_block_index;
     {
         LOCK(cs_main);
         new_block_index = m_node.chainman->ActiveChain().Tip();
     }
-    coin_stats_index.LookUpStats(new_block_index, new_coin_stats);
+    BOOST_CHECK(coin_stats_index.LookUpStats(new_block_index));
 
     BOOST_CHECK(block_index != new_block_index);
 
diff --git a/src/test/fuzz/coins_view.cpp b/src/test/fuzz/coins_view.cpp
index 360dc00307..6c96702f1e 100644
--- a/src/test/fuzz/coins_view.cpp
+++ b/src/test/fuzz/coins_view.cpp
@@ -10,7 +10,6 @@
 #include <consensus/tx_verify.h>
 #include <consensus/validation.h>
 #include <key.h>
-#include <node/coinstats.h>
 #include <policy/policy.h>
 #include <primitives/transaction.h>
 #include <pubkey.h>
@@ -26,10 +25,6 @@
 #include <string>
 #include <vector>
 
-using node::CCoinsStats;
-using node::CoinStatsHashType;
-using node::GetUTXOStats;
-
 namespace {
 const TestingSetup* g_setup;
 const Coin EMPTY_COIN{};
@@ -270,16 +265,6 @@ FUZZ_TARGET_INIT(coins_view, initialize_coins_view)
                 (void)GetTransactionSigOpCost(transaction, coins_view_cache, flags);
             },
             [&] {
-                CCoinsStats stats{CoinStatsHashType::HASH_SERIALIZED};
-                bool expected_code_path = false;
-                try {
-                    (void)GetUTXOStats(&coins_view_cache, g_setup->m_node.chainman->m_blockman, stats);
-                } catch (const std::logic_error&) {
-                    expected_code_path = true;
-                }
-                assert(expected_code_path);
-            },
-            [&] {
                 (void)IsWitnessStandard(CTransaction{random_mutable_transaction}, coins_view_cache);
             });
     }
diff --git a/src/validation.cpp b/src/validation.cpp
index a54ec8269e..44e908152c 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -18,10 +18,10 @@
 #include <cuckoocache.h>
 #include <flatfile.h>
 #include <hash.h>
+#include <kernel/coinstats.h>
 #include <logging.h>
 #include <logging/timer.h>
 #include <node/blockstorage.h>
-#include <node/coinstats.h>
 #include <node/ui_interface.h>
 #include <node/utxo_snapshot.h>
 #include <policy/policy.h>
@@ -58,17 +58,18 @@
 #include <optional>
 #include <string>
 
+using kernel::CCoinsStats;
+using kernel::CoinStatsHashType;
+using kernel::ComputeUTXOStats;
+
 using node::BLOCKFILE_CHUNK_SIZE;
 using node::BlockManager;
 using node::BlockMap;
 using node::CBlockIndexHeightOnlyComparator;
 using node::CBlockIndexWorkComparator;
-using node::CCoinsStats;
-using node::CoinStatsHashType;
 using node::fImporting;
 using node::fPruneMode;
 using node::fReindex;
-using node::GetUTXOStats;
 using node::nPruneTarget;
 using node::OpenBlockFile;
 using node::ReadBlockFromDisk;
@@ -4987,7 +4988,8 @@ bool ChainstateManager::PopulateAndValidateSnapshot(
     CBlockIndex* snapshot_start_block = WITH_LOCK(::cs_main, return m_blockman.LookupBlockIndex(base_blockhash));
 
     if (!snapshot_start_block) {
-        // Needed for GetUTXOStats and ExpectedAssumeutxo to determine the height and to avoid a crash when base_blockhash.IsNull()
+        // Needed for ComputeUTXOStats and ExpectedAssumeutxo to determine the
+        // height and to avoid a crash when base_blockhash.IsNull()
         LogPrintf("[snapshot] Did not find snapshot start blockheader %s\n",
                   base_blockhash.ToString());
         return false;
@@ -5095,22 +5097,22 @@ bool ChainstateManager::PopulateAndValidateSnapshot(
 
     assert(coins_cache.GetBestBlock() == base_blockhash);
 
-    CCoinsStats stats{CoinStatsHashType::HASH_SERIALIZED};
     auto breakpoint_fnc = [] { /* TODO insert breakpoint here? */ };
 
     // As above, okay to immediately release cs_main here since no other context knows
     // about the snapshot_chainstate.
     CCoinsViewDB* snapshot_coinsdb = WITH_LOCK(::cs_main, return &snapshot_chainstate.CoinsDB());
 
-    if (!GetUTXOStats(snapshot_coinsdb, m_blockman, stats, breakpoint_fnc)) {
+    const std::optional<CCoinsStats> maybe_stats = ComputeUTXOStats(CoinStatsHashType::HASH_SERIALIZED, snapshot_coinsdb, m_blockman, breakpoint_fnc);
+    if (!maybe_stats.has_value()) {
         LogPrintf("[snapshot] failed to generate coins stats\n");
         return false;
     }
 
     // Assert that the deserialized chainstate contents match the expected assumeutxo value.
-    if (AssumeutxoHash{stats.hashSerialized} != au_data.hash_serialized) {
+    if (AssumeutxoHash{maybe_stats->hashSerialized} != au_data.hash_serialized) {
         LogPrintf("[snapshot] bad snapshot content hash: expected %s, got %s\n",
-            au_data.hash_serialized.ToString(), stats.hashSerialized.ToString());
+            au_data.hash_serialized.ToString(), maybe_stats->hashSerialized.ToString());
         return false;
     }