Grab iterator at previously executed height

snow/engine/snowman/bootstrap/interval/state.go

@@ -78,6 +78,16 @@ func GetBlockIterator(db database.Iteratee) database.Iterator {
 	return db.NewIteratorWithPrefix(blockPrefix)
 }
 
+// GetBlockIterator returns a block iterator that will produce values
+// corresponding to persisted blocks in order of increasing height starting at
+// [height].
+func GetBlockIteratorWithStart(db database.Iteratee, height uint64) database.Iterator {
+	return db.NewIteratorWithStartAndPrefix(
+		makeBlockKey(height),
+		blockPrefix,
+	)
+}
+
 func GetBlock(db database.KeyValueReader, height uint64) ([]byte, error) {
 	return db.Get(makeBlockKey(height))
 }

snow/engine/snowman/bootstrap/storage.go

@@ -139,7 +139,9 @@ func execute(
 		log("compacting database before executing blocks...")
 		if err := db.Compact(nil, nil); err != nil {
 			// Not a fatal error, log and move on.
-			log("failed to compact bootstrap database before executing blocks", zap.Error(err))
+			log("failed to compact bootstrap database before executing blocks",
+				zap.Error(err),
+			)
 		}
 	}
 
@@ -167,6 +169,25 @@ func execute(
 	)
 	defer func() {
 		iterator.Release()
+
+		halted := haltable.Halted()
+		if !halted {
+			log("compacting database after executing blocks...")
+			if err := db.Compact(nil, nil); err != nil {
+				// Not a fatal error, log and move on.
+				log("failed to compact bootstrap database after executing blocks",
+					zap.Error(err),
+				)
+			}
+		}
+
+		numProcessed := totalNumberToProcess - tree.Len()
+		log("executed blocks",
+			zap.Uint64("numExecuted", numProcessed),
+			zap.Uint64("numToExecute", totalNumberToProcess),
+			zap.Bool("halted", halted),
+			zap.Duration("duration", time.Since(startTime)),
+		)
 	}()
 
 	log("executing blocks",
@@ -208,7 +229,10 @@ func execute(
 
 			processedSinceIteratorRelease = 0
 			iterator.Release()
-			iterator = interval.GetBlockIterator(db)
+			// We specify the starting key of the iterator so that the
+			// underlying database doesn't need to scan over the, potentially
+			// not yet compacted, blocks we just deleted.
+			iterator = interval.GetBlockIteratorWithStart(db, height+1)
 		}
 
 		if now := time.Now(); now.After(timeOfNextLog) {
@@ -248,16 +272,5 @@ func execute(
 	if err := writeBatch(); err != nil {
 		return err
 	}
-	if err := iterator.Error(); err != nil {
-		return err
-	}
-
-	numProcessed := totalNumberToProcess - tree.Len()
-	log("executed blocks",
-		zap.Uint64("numExecuted", numProcessed),
-		zap.Uint64("numToExecute", totalNumberToProcess),
-		zap.Bool("halted", haltable.Halted()),
-		zap.Duration("duration", time.Since(startTime)),
-	)
-	return nil
+	return iterator.Error()
 }