Merge #10557: Make check to distinguish between orphan txs and old txs more efficient.

18bacec Make check to distinguish between orphan txs and old txs more efficient. (Alex Morcos)

Tree-SHA512: b6b4bad89aa561975dce7b68b2fdad5623af5ebcb9c38fd6a72b5f6d0544ed441df4865591ac018f7ae0df9b5c60820cb4d9e55664f5667c9268458df70fd554

Author: sipa

src/validation.cpp

@@ -532,24 +532,20 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
         CCoinsViewMemPool viewMemPool(pcoinsTip, pool);
         view.SetBackend(viewMemPool);
 
-        // do we already have it?
-        for (size_t out = 0; out < tx.vout.size(); out++) {
-            COutPoint outpoint(hash, out);
-            bool had_coin_in_cache = pcoinsTip->HaveCoinInCache(outpoint);
-            if (view.HaveCoin(outpoint)) {
-                if (!had_coin_in_cache) {
-                    coins_to_uncache.push_back(outpoint);
-                }
-                return state.Invalid(false, REJECT_DUPLICATE, "txn-already-known");
-            }
-        }
-
         // do all inputs exist?
         for (const CTxIn txin : tx.vin) {
             if (!pcoinsTip->HaveCoinInCache(txin.prevout)) {
                 coins_to_uncache.push_back(txin.prevout);
             }
             if (!view.HaveCoin(txin.prevout)) {
+                // Are inputs missing because we already have the tx?
+                for (size_t out = 0; out < tx.vout.size(); out++) {
+                    // Optimistically just do efficient check of cache for outputs
+                    if (pcoinsTip->HaveCoinInCache(COutPoint(hash, out))) {
+                        return state.Invalid(false, REJECT_DUPLICATE, "txn-already-known");
+                    }
+                }
+                // Otherwise assume this might be an orphan tx for which we just haven't seen parents yet
                 if (pfMissingInputs) {
                     *pfMissingInputs = true;
                 }