From aed16621c0e5b3b14c11360e6432375df87dcae4 Mon Sep 17 00:00:00 2001
From: zhulongcheng <zhulongcheng.me@gmail.com>
Date: Mon, 1 Apr 2019 16:19:06 +0800
Subject: [PATCH] Add Head.compactable method (#542)

* Add Head.compactable method

Signed-off-by: zhulongcheng <zhulongcheng.me@gmail.com>
---
 db.go   | 8 +++-----
 head.go | 7 +++++++
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/db.go b/db.go
index 80f8debdd..2ed31ea5f 100644
--- a/db.go
+++ b/db.go
@@ -391,7 +391,7 @@ func (a dbAppender) Commit() error {
 
 	// We could just run this check every few minutes practically. But for benchmarks
 	// and high frequency use cases this is the safer way.
-	if a.db.head.MaxTime()-a.db.head.MinTime() > a.db.head.chunkRange/2*3 {
+	if a.db.head.compactable() {
 		select {
 		case a.db.compactc <- struct{}{}:
 		default:
@@ -418,13 +418,11 @@ func (db *DB) compact() (err error) {
 			return nil
 		default:
 		}
-		// The head has a compactable range if 1.5 level 0 ranges are between the oldest
-		// and newest timestamp. The 0.5 acts as a buffer of the appendable window.
-		if db.head.MaxTime()-db.head.MinTime() <= db.opts.BlockRanges[0]/2*3 {
+		if !db.head.compactable() {
 			break
 		}
 		mint := db.head.MinTime()
-		maxt := rangeForTimestamp(mint, db.opts.BlockRanges[0])
+		maxt := rangeForTimestamp(mint, db.head.chunkRange)
 
 		// Wrap head into a range that bounds all reads to it.
 		head := &rangeHead{
diff --git a/head.go b/head.go
index 093042702..26a42fb33 100644
--- a/head.go
+++ b/head.go
@@ -1020,6 +1020,13 @@ func (h *Head) MaxTime() int64 {
 	return atomic.LoadInt64(&h.maxTime)
 }
 
+// compactable returns whether the head has a compactable range.
+// The head has a compactable range when the head time range is 1.5 times the chunk range.
+// The 0.5 acts as a buffer of the appendable window.
+func (h *Head) compactable() bool {
+	return h.MaxTime()-h.MinTime() > h.chunkRange/2*3
+}
+
 // Close flushes the WAL and closes the head.
 func (h *Head) Close() error {
 	if h.wal == nil {