From c75cbb2c45799e5e58512c265d3302a87b377a3b Mon Sep 17 00:00:00 2001
From: Harshit Gangal <harshit@planetscale.com>
Date: Fri, 3 Jan 2025 16:47:53 +0530
Subject: [PATCH] vexplain to protect the log fields from concurrent writes

Signed-off-by: Harshit Gangal <harshit@planetscale.com>
---
 go/vt/vtgate/executorcontext/vcursor_impl.go | 31 +++++++++++++-------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/go/vt/vtgate/executorcontext/vcursor_impl.go b/go/vt/vtgate/executorcontext/vcursor_impl.go
index 40317f5103a..df989fd7a67 100644
--- a/go/vt/vtgate/executorcontext/vcursor_impl.go
+++ b/go/vt/vtgate/executorcontext/vcursor_impl.go
@@ -22,6 +22,7 @@ import (
 	"io"
 	"sort"
 	"strings"
+	"sync"
 	"sync/atomic"
 	"time"
 
@@ -154,6 +155,8 @@ type (
 
 		observer ResultsObserver
 
+		// this protects the interOpStats and shardsStats fields from concurrent writes
+		mu sync.Mutex
 		// this is a map of the number of rows that every primitive has returned
 		// if this field is nil, it means that we are not logging operator traffic
 		interOpStats map[engine.Primitive]engine.RowsReceived
@@ -642,21 +645,29 @@ func (vc *VCursorImpl) ExecutePrimitive(ctx context.Context, primitive engine.Pr
 }
 
 func (vc *VCursorImpl) logOpTraffic(primitive engine.Primitive, res *sqltypes.Result) {
-	if vc.interOpStats != nil {
-		rows := vc.interOpStats[primitive]
-		if res == nil {
-			rows = append(rows, 0)
-		} else {
-			rows = append(rows, len(res.Rows))
-		}
-		vc.interOpStats[primitive] = rows
+	if vc.interOpStats == nil {
+		return
+	}
+
+	vc.mu.Lock()
+	defer vc.mu.Unlock()
+
+	rows := vc.interOpStats[primitive]
+	if res == nil {
+		rows = append(rows, 0)
+	} else {
+		rows = append(rows, len(res.Rows))
 	}
+	vc.interOpStats[primitive] = rows
 }
 
 func (vc *VCursorImpl) logShardsQueried(primitive engine.Primitive, shardsNb int) {
-	if vc.shardsStats != nil {
-		vc.shardsStats[primitive] += engine.ShardsQueried(shardsNb)
+	if vc.shardsStats == nil {
+		return
 	}
+	vc.mu.Lock()
+	defer vc.mu.Unlock()
+	vc.shardsStats[primitive] += engine.ShardsQueried(shardsNb)
 }
 
 func (vc *VCursorImpl) ExecutePrimitiveStandalone(ctx context.Context, primitive engine.Primitive, bindVars map[string]*querypb.BindVariable, wantfields bool) (*sqltypes.Result, error) {