core: make reorg use less memory

core/blockchain.go

@@ -2029,20 +2029,16 @@ func (bc *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
 	}
 	// Insert the new chain(except the head block(reverse order)),
 	// taking care of the proper incremental order.
+	log.Warn("Long reorg", "newchain length", len(newChain), "from", newChain[0].number, "to", newChain[len(newChain)-1].number)
 	for i := len(newChain) - 1; i >= 1; i-- {
 		// Insert the block in the canonical way, re-writing history
 		block := bc.GetBlock(newChain[i].hash, newChain[i].number)
 
 		bc.writeHeadBlock(block)
-
-		// Collect reborn logs due to chain reorg
-		logs := bc.collectLogs(block.Hash(), false)
-		if len(logs) > 0 {
-			rebirthLogs = append(rebirthLogs, logs)
-		}
 		// Collect the new added transactions.
 		addedTxs = append(addedTxs, block.Transactions()...)
 	}
+
 	// Delete useless indexes right now which includes the non-canonical
 	// transaction indexes, canonical chain indexes which above the head.
 	indexesBatch := bc.db.NewBatch()
@@ -2061,6 +2057,15 @@ func (bc *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
 	if err := indexesBatch.Write(); err != nil {
 		log.Crit("Failed to delete useless indexes", "err", err)
 	}
+
+	// Collect the logs
+	for i := len(newChain) - 1; i >= 1; i-- {
+		// Collect reborn logs due to chain reorg
+		logs := bc.collectLogs(newChain[i].hash, false)
+		if len(logs) > 0 {
+			rebirthLogs = append(rebirthLogs, logs)
+		}
+	}
 	// If any logs need to be fired, do it now. In theory we could avoid creating
 	// this goroutine if there are no events to fire, but realistcally that only
 	// ever happens if we're reorging empty blocks, which will only happen on idle