Revert "Comments, disable dead code (twins collection)."

This reverts commit 4448760.

Author: evoskuil

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

@@ -142,23 +142,6 @@ code CLASS::set_code(const tx_link& tx_fk, const transaction& tx) NOEXCEPT
 
     // Commit points (hashmap).
     {
-        ////if (!tx.is_coinbase())
-        ////{
-        ////    const auto ptr = store_.point.get_memory();
-        ////    for (const auto& in: *ins)
-        ////    {
-        ////        // Extract integer and modulo to get % of points.
-        ////        // Simulates bloom filtering false positive duplicate confirm.
-        ////        if (to_bool(unique_hash(in->point().hash()) % 1_size))
-        ////            continue;
-        ////
-        ////        // In a normal test run it will not exist (cb excluded above).
-        ////        // Return failure to ensure this is not elided by the compiler.
-        ////        if (store_.point.exists(ptr, in->point()))
-        ////            return error::confirmed_double_spend;
-        ////    }
-        ////}
-
         // Expand synchronizes keys with ins_fk, entries dropped into same offset.
         // Allocate contiguous points (at sequential keys matching ins_fk).
         if (!store_.point.expand(ins_fk + inputs))
@@ -167,12 +150,27 @@ code CLASS::set_code(const tx_link& tx_fk, const transaction& tx) NOEXCEPT
         // This must be set after tx.set and before tx.commit, since searchable and
         // produces an association to tx.link, and is also an integral part of tx.
         const auto ptr = store_.point.get_memory();
+
+        // Collect duplicates to store in duplicate table.
+        std::vector<chain::cref_point> twins{};
         for (const auto& in: *ins)
         {
-            if (!store_.point.put(ptr, ins_fk++, in->point(),
+            ///////////////////////////////////////////////////////////////////
+            // TODO: add filter to hashmap and use method here to detect and
+            // TODO: return prior existence (dup) here (insert succeeds).
+            ///////////////////////////////////////////////////////////////////
+            bool twin{};
+            if (!store_.point.put(/*twin,*/ ptr, ins_fk++, in->point(),
                 table::point::record{}))
                 return error::tx_point_put;
+
+            if (twin)
+                twins.emplace_back(in->point().hash(), in->point().index());
         }
+
+        ///////////////////////////////////////////////////////////////////////
+        // TODO: if (!twins.empty()) ... store to duplicate table here.
+        ///////////////////////////////////////////////////////////////////////
     }
 
     // Commit address index records (hashmap).