Add to_transaction(header_link, position).

include/bitcoin/database/impl/query/translate.ipp

@@ -411,33 +411,44 @@ output_links CLASS::to_block_prevouts(const header_link& link) const NOEXCEPT
 // ----------------------------------------------------------------------------
 
 TEMPLATE
-tx_link CLASS::to_coinbase(const header_link& link) const NOEXCEPT
+tx_links CLASS::to_transactions(const header_link& link) const NOEXCEPT
 {
-    table::txs::get_coinbase txs{};
+    table::txs::get_txs txs{};
     if (!store_.txs.at(to_txs(link), txs))
         return {};
 
-    return txs.coinbase_fk;
+    return std::move(txs.tx_fks);
 }
 
 TEMPLATE
-tx_links CLASS::to_transactions(const header_link& link) const NOEXCEPT
+tx_links CLASS::to_spending_txs(const header_link& link) const NOEXCEPT
 {
-    table::txs::get_txs txs{};
+    table::txs::get_spending_txs txs{};
     if (!store_.txs.at(to_txs(link), txs))
         return {};
 
     return std::move(txs.tx_fks);
 }
 
 TEMPLATE
-tx_links CLASS::to_spending_txs(const header_link& link) const NOEXCEPT
+tx_link CLASS::to_coinbase(const header_link& link) const NOEXCEPT
 {
-    table::txs::get_spending_txs txs{};
+    table::txs::get_coinbase txs{};
     if (!store_.txs.at(to_txs(link), txs))
         return {};
 
-    return std::move(txs.tx_fks);
+    return txs.coinbase_fk;
+}
+
+TEMPLATE
+tx_link CLASS::to_transaction(const header_link& link,
+    size_t position) const NOEXCEPT
+{
+    table::txs::get_tx txs{ {}, position };
+    if (!store_.txs.at(to_txs(link), txs))
+        return {};
+
+    return txs.tx_fk;
 }
 
 // header to arraymap tables (guard domain transitions)

include/bitcoin/database/query.hpp

@@ -314,9 +314,11 @@ class query
     output_links to_block_prevouts(const header_link& link) const NOEXCEPT;
 
     /// block to txs (forward navigation)
-    tx_link to_coinbase(const header_link& link) const NOEXCEPT;
     tx_links to_transactions(const header_link& link) const NOEXCEPT;
     tx_links to_spending_txs(const header_link& link) const NOEXCEPT;
+    tx_link to_coinbase(const header_link& link) const NOEXCEPT;
+    tx_link to_transaction(const header_link& link,
+        size_t position) const NOEXCEPT;
 
     /// header to arraymap tables (guard domain transitions)
     constexpr size_t to_validated_bk(const header_link& link) const NOEXCEPT;

include/bitcoin/database/tables/archives/txs.hpp

@@ -171,6 +171,34 @@ struct txs
         tx::integer coinbase_fk{};
     };
 
+    struct get_tx
+      : public schema::txs
+    {
+        link count() const NOEXCEPT
+        {
+            BC_ASSERT(false);
+            return {};
+        }
+
+        inline bool from_data(reader& source) NOEXCEPT
+        {
+            const auto number = source.read_little_endian<ct::integer, ct::size>();
+            source.skip_bytes(bytes::size);
+            if (number > position)
+            {
+                source.skip_bytes(position * tx::size);
+                tx_fk = source.read_little_endian<tx::integer, tx::size>();
+                return source;
+            }
+
+            source.invalidate();
+            return source;
+        }
+
+        const size_t position{};
+        tx::integer tx_fk{};
+    };
+
     struct get_block_size
       : public schema::txs
     {