From 0fa6df94a23ae28e8551ab31c0aa393c2c415662 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Thu, 26 Sep 2019 14:15:52 +0300
Subject: [PATCH] lib/storage: optimize TSID comparison

---
 lib/storage/raw_row.go | 40 ++++++++++++++--------------------------
 lib/storage/tsid.go    | 36 +++++++++---------------------------
 2 files changed, 23 insertions(+), 53 deletions(-)

diff --git a/lib/storage/raw_row.go b/lib/storage/raw_row.go
index c738e29f4..b1d978d33 100644
--- a/lib/storage/raw_row.go
+++ b/lib/storage/raw_row.go
@@ -48,42 +48,30 @@ type rawRowsSort []rawRow
 func (rrs *rawRowsSort) Len() int { return len(*rrs) }
 func (rrs *rawRowsSort) Less(i, j int) bool {
 	x := *rrs
+	if i < 0 || j < 0 || i >= len(x) || j >= len(x) {
+		// This is no-op for compiler, so it doesn't generate panic code
+		// for out of range access on x[i], x[j] below
+		return false
+	}
 	a := &x[i]
 	b := &x[j]
 	ta := &a.TSID
 	tb := &b.TSID
-	if ta.MetricID == tb.MetricID {
-		// Fast path - identical TSID values.
-		return a.Timestamp < b.Timestamp
-	}
 
-	// Slow path - compare TSIDs.
 	// Manually inline TSID.Less here, since the compiler doesn't inline it yet :(
-	if ta.MetricGroupID < tb.MetricGroupID {
-		return true
+	if ta.MetricGroupID != tb.MetricGroupID {
+		return ta.MetricGroupID < tb.MetricGroupID
 	}
-	if ta.MetricGroupID > tb.MetricGroupID {
-		return false
+	if ta.JobID != tb.JobID {
+		return ta.JobID < tb.JobID
 	}
-	if ta.JobID < tb.JobID {
-		return true
+	if ta.InstanceID != tb.InstanceID {
+		return ta.InstanceID < tb.InstanceID
 	}
-	if ta.JobID > tb.JobID {
-		return false
+	if ta.MetricID != tb.MetricID {
+		return ta.MetricID < tb.MetricID
 	}
-	if ta.InstanceID < tb.InstanceID {
-		return true
-	}
-	if ta.InstanceID > tb.InstanceID {
-		return false
-	}
-	if ta.MetricID < tb.MetricID {
-		return true
-	}
-	if ta.MetricID > tb.MetricID {
-		return false
-	}
-	return false
+	return a.Timestamp < b.Timestamp
 }
 func (rrs *rawRowsSort) Swap(i, j int) {
 	x := *rrs
diff --git a/lib/storage/tsid.go b/lib/storage/tsid.go
index 210787a3b..7e3904e9a 100644
--- a/lib/storage/tsid.go
+++ b/lib/storage/tsid.go
@@ -88,34 +88,16 @@ func (t *TSID) Unmarshal(src []byte) ([]byte, error) {
 
 // Less return true if t < b.
 func (t *TSID) Less(b *TSID) bool {
-	if t.MetricID == b.MetricID {
-		// Fast path - two TSID values are identical.
-		return false
+	// Do not compare MetricIDs here as fast path for determining identical TSIDs,
+	// since identical TSIDs aren't passed here in hot paths.
+	if t.MetricGroupID != b.MetricGroupID {
+		return t.MetricGroupID < b.MetricGroupID
 	}
-
-	if t.MetricGroupID < b.MetricGroupID {
-		return true
+	if t.JobID != b.JobID {
+		return t.JobID < b.JobID
 	}
-	if t.MetricGroupID > b.MetricGroupID {
-		return false
+	if t.InstanceID != b.InstanceID {
+		return t.InstanceID < b.InstanceID
 	}
-	if t.JobID < b.JobID {
-		return true
-	}
-	if t.JobID > b.JobID {
-		return false
-	}
-	if t.InstanceID < b.InstanceID {
-		return true
-	}
-	if t.InstanceID > b.InstanceID {
-		return false
-	}
-	if t.MetricID < b.MetricID {
-		return true
-	}
-	if t.MetricID > b.MetricID {
-		return false
-	}
-	return false
+	return t.MetricID < b.MetricID
 }