Merge #7056: Save last db read

8504867 Save the last unnecessary database read (Alex Morcos)

src/coins.cpp

@@ -117,11 +117,17 @@ CCoinsModifier CCoinsViewCache::ModifyCoins(const uint256 &txid) {
     return CCoinsModifier(*this, ret.first, cachedCoinUsage);
 }
 
-CCoinsModifier CCoinsViewCache::ModifyNewCoins(const uint256 &txid) {
+// ModifyNewCoins has to know whether the new outputs its creating are for a
+// coinbase or not.  If they are for a coinbase, it can not mark them as fresh.
+// This is to ensure that the historical duplicate coinbases before BIP30 was
+// in effect will still be properly overwritten when spent.
+CCoinsModifier CCoinsViewCache::ModifyNewCoins(const uint256 &txid, bool coinbase) {
     assert(!hasModifier);
     std::pair<CCoinsMap::iterator, bool> ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry()));
     ret.first->second.coins.Clear();
-    ret.first->second.flags = CCoinsCacheEntry::FRESH;
+    if (!coinbase) {
+        ret.first->second.flags = CCoinsCacheEntry::FRESH;
+    }
     ret.first->second.flags |= CCoinsCacheEntry::DIRTY;
     return CCoinsModifier(*this, ret.first, 0);
 }

src/coins.h

@@ -435,7 +435,7 @@ public:
      * would not properly overwrite the first coinbase of the pair. Simultaneous modifications
      * are not allowed.
      */
-    CCoinsModifier ModifyNewCoins(const uint256 &txid);
+    CCoinsModifier ModifyNewCoins(const uint256 &txid, bool coinbase);
 
     /**
      * Push the modifications applied to this cache to its base.

src/main.cpp

@@ -1546,17 +1546,9 @@ void UpdateCoins(const CTransaction& tx, CValidationState &state, CCoinsViewCach
                 undo.nVersion = coins->nVersion;
             }
         }
-        // add outputs
-        inputs.ModifyNewCoins(tx.GetHash())->FromTx(tx, nHeight);
-    }
-    else {
-        // add outputs for coinbase tx
-        // In this case call the full ModifyCoins which will do a database
-        // lookup to be sure the coins do not already exist otherwise we do not
-        // know whether to mark them fresh or not.  We want the duplicate coinbases
-        // before BIP30 to still be properly overwritten.
-        inputs.ModifyCoins(tx.GetHash())->FromTx(tx, nHeight);
     }
+    // add outputs
+    inputs.ModifyNewCoins(tx.GetHash(), tx.IsCoinBase())->FromTx(tx, nHeight);
 }
 
 void UpdateCoins(const CTransaction& tx, CValidationState &state, CCoinsViewCache &inputs, int nHeight)