From 5c317c55e77c4783e089db653983c394742a6c52 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B8rn=20Erik=20Pedersen?=
 <bjorn.erik.pedersen@gmail.com>
Date: Wed, 1 Mar 2023 14:59:08 +0100
Subject: [PATCH] Move the Related doc counter to prevent a race

Closes #10768
---
 related/inverted_index.go | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/related/inverted_index.go b/related/inverted_index.go
index 967855133..ae894e522 100644
--- a/related/inverted_index.go
+++ b/related/inverted_index.go
@@ -143,13 +143,6 @@ type IndexConfig struct {
 	// Will lower case all string values in and queries tothis index.
 	// May get better accurate results, but at a slight performance cost.
 	ToLower bool
-
-	// Counts the number of documents in the index.
-	numDocs int
-}
-
-func (cfg *IndexConfig) incrNumDocs() {
-	cfg.numDocs++
 }
 
 // Document is the interface an indexable document in Hugo must fulfill.
@@ -178,6 +171,8 @@ type FragmentProvider interface {
 type InvertedIndex struct {
 	cfg   Config
 	index map[string]map[Keyword][]Document
+	// Counts the number of documents added to each index.
+	indexDocCount map[string]int
 
 	minWeight int
 	maxWeight int
@@ -199,7 +194,7 @@ func (idx *InvertedIndex) getIndexCfg(name string) (IndexConfig, bool) {
 // NewInvertedIndex creates a new InvertedIndex.
 // Documents to index must be added in Add.
 func NewInvertedIndex(cfg Config) *InvertedIndex {
-	idx := &InvertedIndex{index: make(map[string]map[Keyword][]Document), cfg: cfg}
+	idx := &InvertedIndex{index: make(map[string]map[Keyword][]Document), indexDocCount: make(map[string]int), cfg: cfg}
 	for _, conf := range cfg.Indices {
 		idx.index[conf.Name] = make(map[Keyword][]Document)
 		if conf.Weight < idx.minWeight {
@@ -221,7 +216,7 @@ func (idx *InvertedIndex) Add(ctx context.Context, docs ...Document) error {
 		panic("index is finalized")
 	}
 	var err error
-	for i, config := range idx.cfg.Indices {
+	for _, config := range idx.cfg.Indices {
 		if config.Weight == 0 {
 			// Disabled
 			continue
@@ -251,8 +246,7 @@ func (idx *InvertedIndex) Add(ctx context.Context, docs ...Document) error {
 			}
 
 			if added {
-				c := &idx.cfg.Indices[i]
-				(*c).incrNumDocs()
+				idx.indexDocCount[config.Name]++
 			}
 		}
 	}
@@ -270,12 +264,12 @@ func (idx *InvertedIndex) Finalize(ctx context.Context) error {
 			continue
 		}
 		setm := idx.index[config.Name]
-		numDocs := config.numDocs
-		if numDocs == 0 {
+		if idx.indexDocCount[config.Name] == 0 {
 			continue
 		}
 
 		// Remove high cardinality terms.
+		numDocs := idx.indexDocCount[config.Name]
 		for k, v := range setm {
 			percentageWithKeyword := int(math.Ceil(float64(len(v)) / float64(numDocs) * 100))
 			if percentageWithKeyword > config.CardinalityThreshold {