From e76fada2d200e026fed8ca24f0a7e2fa1595be97 Mon Sep 17 00:00:00 2001
From: Dave Collins <davec@conformal.com>
Date: Tue, 29 Oct 2013 15:48:22 -0500
Subject: [PATCH] Optimize NotifyNewTxListener.

Looking up transactions from the database is an expensive operation.
This commit modifies the NotifyNewTxListener code to simply iterate the
transactions in the block instead of looking them up from the db.

Currently the wallet code needs a spent flag which ultimately shouldn't be
required.  For now, the spent data is simply created on the fly which is
still significantly faster than doing database transaction lookups.

Closes #24.
---
 rpcserver.go | 47 ++++++++++++++++++++++++++++++++---------------
 1 file changed, 32 insertions(+), 15 deletions(-)

diff --git a/rpcserver.go b/rpcserver.go
index 8990c6ec..e02c81c3 100644
--- a/rpcserver.go
+++ b/rpcserver.go
@@ -1169,26 +1169,43 @@ func (s *rpcServer) NotifyBlockDisconnected(block *btcutil.Block) {
 // of new transactions (with both spent and unspent outputs) for a watched
 // address.
 func (s *rpcServer) NotifyBlockTXs(db btcdb.Db, block *btcutil.Block) {
-	txShaList, err := block.TxShas()
-	if err != nil {
-		log.Error("Bad block; All notifications for block dropped.")
-		return
+	// Build a map of in-flight transactions to see if any of the inputs in
+	// this block are referencing other transactions earlier in this block.
+	txInFlight := map[btcwire.ShaHash]int{}
+	transactions := block.Transactions()
+	spent := make([][]bool, len(transactions))
+	for i, tx := range transactions {
+		spent[i] = make([]bool, len(tx.MsgTx().TxOut))
+		txInFlight[*tx.Sha()] = i
 	}
-	txList := db.FetchTxByShaList(txShaList)
-	for _, txReply := range txList {
-		if txReply.Err == nil && txReply.Tx != nil {
-			go s.newBlockNotifyCheckTxIn(txReply.Tx.TxIn)
-			go s.newBlockNotifyCheckTxOut(db, block, txReply)
+
+	// The newBlockNotifyCheckTxOut current needs spent data.  This can
+	// this can ultimately be optimized out by making sure the notifications
+	// are in order.  For now, just create the spent data.
+	for i, tx := range transactions[1:] {
+		for _, txIn := range tx.MsgTx().TxIn {
+			originHash := &txIn.PreviousOutpoint.Hash
+			if inFlightIndex, ok := txInFlight[*originHash]; ok &&
+				i >= inFlightIndex {
+
+				prevIndex := txIn.PreviousOutpoint.Index
+				spent[inFlightIndex][prevIndex] = true
+			}
 		}
 	}
+
+	for i, tx := range transactions {
+		go s.newBlockNotifyCheckTxIn(tx)
+		go s.newBlockNotifyCheckTxOut(block, tx, spent[i])
+	}
 }
 
 // newBlockNotifyCheckTxIn is a helper function to iterate through
 // each transaction input of a new block and perform any checks and
 // notify listening frontends when necessary.
-func (s *rpcServer) newBlockNotifyCheckTxIn(txins []*btcwire.TxIn) {
+func (s *rpcServer) newBlockNotifyCheckTxIn(tx *btcutil.Tx) {
 	for wltNtfn, cxt := range s.ws.requests.m {
-		for _, txin := range txins {
+		for _, txin := range tx.MsgTx().TxIn {
 			for op, id := range cxt.spentRequests {
 				if txin.PreviousOutpoint != op {
 					continue
@@ -1220,9 +1237,9 @@ func (s *rpcServer) newBlockNotifyCheckTxIn(txins []*btcwire.TxIn) {
 // newBlockNotifyCheckTxOut is a helper function to iterate through
 // each transaction output of a new block and perform any checks and
 // notify listening frontends when necessary.
-func (s *rpcServer) newBlockNotifyCheckTxOut(db btcdb.Db, block *btcutil.Block, tx *btcdb.TxListReply) {
+func (s *rpcServer) newBlockNotifyCheckTxOut(block *btcutil.Block, tx *btcutil.Tx, spent []bool) {
 	for wltNtfn, cxt := range s.ws.requests.m {
-		for i, txout := range tx.Tx.TxOut {
+		for i, txout := range tx.MsgTx().TxOut {
 			_, txaddrhash, err := btcscript.ScriptToAddrHash(txout.PkScript)
 			if err != nil {
 				log.Debug("Error getting payment address from tx; dropping any Tx notifications.")
@@ -1258,11 +1275,11 @@ func (s *rpcServer) newBlockNotifyCheckTxOut(db btcdb.Db, block *btcutil.Block,
 						Receiver:  txaddr,
 						BlockHash: blkhash.String(),
 						Height:    block.Height(),
-						TxHash:    tx.Sha.String(),
+						TxHash:    tx.Sha().String(),
 						Index:     uint32(i),
 						Amount:    txout.Value,
 						PkScript:  btcutil.Base58Encode(txout.PkScript),
-						Spent:     tx.TxSpent[i],
+						Spent:     spent[i],
 					},
 					Error: nil,
 					Id:    &id,