From e53f9e553d2b7cab73b03fa1c334dbaeaea11533 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Tue, 5 Nov 2019 12:57:45 +0200
Subject: [PATCH] lib/storage: try potentially faster tag filters at first,
 then apply slower tag filters

The fastest tag filters are non-negative non-regexp, since they are the most specific.
The slowest tag filters are negative regexp, since they require scanning
all the entries for the given label.
---
 lib/storage/index_db.go | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/lib/storage/index_db.go b/lib/storage/index_db.go
index 3e270fd37c..215eff241c 100644
--- a/lib/storage/index_db.go
+++ b/lib/storage/index_db.go
@@ -1544,7 +1544,22 @@ func (is *indexSearch) searchMetricIDs(tfss []*TagFilters, tr TimeRange, maxMetr
 
 func (is *indexSearch) updateMetricIDsForTagFilters(metricIDs *uint64set.Set, tfs *TagFilters, tr TimeRange, maxMetrics int) error {
 	// Sort tag filters for faster ts.Seek below.
-	sort.Slice(tfs.tfs, func(i, j int) bool { return bytes.Compare(tfs.tfs[i].prefix, tfs.tfs[j].prefix) < 0 })
+	sort.Slice(tfs.tfs, func(i, j int) bool {
+		// Move regexp and negative filters to the end, since they require scanning
+		// all the entries for the given label.
+		a := &tfs.tfs[i]
+		b := &tfs.tfs[j]
+		if a.isRegexp != b.isRegexp {
+			return !a.isRegexp
+		}
+		if a.isNegative != b.isNegative {
+			return !a.isNegative
+		}
+		if len(a.orSuffixes) != len(b.orSuffixes) {
+			return len(a.orSuffixes) < len(b.orSuffixes)
+		}
+		return bytes.Compare(a.prefix, b.prefix) < 0
+	})
 
 	minTf, minMetricIDs, err := is.getTagFilterWithMinMetricIDsCountOptimized(tfs, tr, maxMetrics)
 	if err != nil {