From c76a904bb0d01bf1bba44fcd01f7433a5cbaf1a9 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Sun, 7 Mar 2021 21:12:28 +0200
Subject: [PATCH] lib/storage: tune loopsCount estimations in
 getMetricIDsForTagFilterSlow

The adjusted estmations give up to 2x lower median response times on 200qps /api/v1/query_range workload
---
 lib/storage/index_db.go | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/storage/index_db.go b/lib/storage/index_db.go
index e56bcb550..35a06c9cf 100644
--- a/lib/storage/index_db.go
+++ b/lib/storage/index_db.go
@@ -154,8 +154,8 @@ func openIndexDB(path string, metricIDCache, metricNameCache, tsidCache *working
 		metricIDCache:              metricIDCache,
 		metricNameCache:            metricNameCache,
 		tsidCache:                  tsidCache,
-		uselessTagFiltersCache:     workingsetcache.New(mem/128, 3*time.Hour),
-		loopsPerDateTagFilterCache: workingsetcache.New(mem/128, 3*time.Hour),
+		uselessTagFiltersCache:     workingsetcache.New(mem/128, time.Hour),
+		loopsPerDateTagFilterCache: workingsetcache.New(mem/128, time.Hour),
 
 		minTimestampForCompositeIndex: minTimestampForCompositeIndex,
 	}
@@ -2483,7 +2483,8 @@ func (is *indexSearch) getMetricIDsForTagFilterSlow(tf *tagFilter, filter *uint6
 		}
 		// Slow path: need tf.matchSuffix call.
 		ok, err := tf.matchSuffix(suffix)
-		loopsCount += tf.matchCost
+		// Assume that tf.matchSuffix call needs 10x more time than a single metric scan iteration.
+		loopsCount += 10*tf.matchCost
 		if err != nil {
 			return loopsCount, fmt.Errorf("error when matching %s against suffix %q: %w", tf, suffix, err)
 		}
@@ -2504,8 +2505,8 @@ func (is *indexSearch) getMetricIDsForTagFilterSlow(tf *tagFilter, filter *uint6
 			}
 			kb.B[len(kb.B)-1]++
 			ts.Seek(kb.B)
-			// Assume that a seek cost is equivalent to 100 ordinary loops.
-			loopsCount += 100
+			// Assume that a seek cost is equivalent to 1000 ordinary loops.
+			loopsCount += 1000
 			continue
 		}
 		prevMatch = true