From b7c44147f0adfdee9ebfac56dc087beebbe171b4 Mon Sep 17 00:00:00 2001
From: Brian Brazil <brian.brazil@robustperception.io>
Date: Sat, 4 Apr 2020 13:07:12 +0100
Subject: [PATCH] Add hint that the series endpoint is being used to the tsdb.

Currently the series endpoint is paging in all chunks for
matched series, which can be rather slow.

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>
---
 tsdb/querier.go   | 7 +++++++
 web/api/v1/api.go | 8 +++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/tsdb/querier.go b/tsdb/querier.go
index 05221127c..9b6219b2c 100644
--- a/tsdb/querier.go
+++ b/tsdb/querier.go
@@ -207,6 +207,13 @@ func (q *blockQuerier) Select(sortSeries bool, hints *storage.SelectHints, ms ..
 	if hints != nil {
 		mint = hints.Start
 		maxt = hints.End
+		if hints.Func == "series" { // The series API does not need any chunks loaded.
+			return &blockSeriesSet{
+				set:  base,
+				mint: mint,
+				maxt: maxt,
+			}, nil, nil
+		}
 	}
 	return &blockSeriesSet{
 		set: &populatedChunkSeries{
diff --git a/web/api/v1/api.go b/web/api/v1/api.go
index 7188e08ff..5c2dac2eb 100644
--- a/web/api/v1/api.go
+++ b/web/api/v1/api.go
@@ -528,10 +528,16 @@ func (api *API) series(r *http.Request) apiFuncResult {
 	}
 	defer q.Close()
 
+	hints := &storage.SelectHints{
+		Start: timestamp.FromTime(start),
+		End:   timestamp.FromTime(end),
+		Func:  "series", // There is no series function.
+	}
+
 	var sets []storage.SeriesSet
 	var warnings storage.Warnings
 	for _, mset := range matcherSets {
-		s, wrn, err := q.Select(false, nil, mset...)
+		s, wrn, err := q.Select(false, hints, mset...)
 		warnings = append(warnings, wrn...)
 		if err != nil {
 			return apiFuncResult{nil, &apiError{errorExec, err}, warnings, nil}