executor: fix data race at the ShowExec (#39817)

close #39816, close #40295

Author: hawkingrei

executor/BUILD.bazel

@@ -192,6 +192,7 @@ go_library(
         "//util/servermemorylimit",
         "//util/set",
         "//util/size",
+        "//util/slice",
         "//util/sqlexec",
         "//util/stmtsummary",
         "//util/stringutil",

executor/show.go

@@ -69,6 +69,7 @@ import (
 	"github.com/pingcap/tidb/util/memory"
 	"github.com/pingcap/tidb/util/sem"
 	"github.com/pingcap/tidb/util/set"
+	"github.com/pingcap/tidb/util/slice"
 	"github.com/pingcap/tidb/util/sqlexec"
 	"github.com/pingcap/tidb/util/stringutil"
 	"golang.org/x/exp/slices"
@@ -306,13 +307,14 @@ func (v *visibleChecker) Leave(in ast.Node) (out ast.Node, ok bool) {
 }
 
 func (e *ShowExec) fetchShowBind() error {
-	var bindRecords []*bindinfo.BindRecord
+	var tmp []*bindinfo.BindRecord
 	if !e.GlobalScope {
 		handle := e.ctx.Value(bindinfo.SessionBindInfoKeyType).(*bindinfo.SessionHandle)
-		bindRecords = handle.GetAllBindRecord()
+		tmp = handle.GetAllBindRecord()
 	} else {
-		bindRecords = domain.GetDomain(e.ctx).BindHandle().GetAllBindRecord()
+		tmp = domain.GetDomain(e.ctx).BindHandle().GetAllBindRecord()
 	}
+	bindRecords := slice.Copy(tmp)
 	// Remove the invalid bindRecord.
 	ind := 0
 	for _, bindData := range bindRecords {

util/slice/slice.go

@@ -39,3 +39,16 @@ func AllOf(s interface{}, p func(int) bool) bool {
 	}
 	return NoneOf(s, np)
 }
+
+// Copy is a deep copy of the slice.
+func Copy[T any](a []*T) []*T {
+	b := make([]*T, len(a))
+	for i, p := range a {
+		if p == nil {
+			continue
+		}
+		v := *p
+		b[i] = &v
+	}
+	return b
+}

util/slice/slice_test.go

@@ -43,3 +43,19 @@ func TestSlice(t *testing.T) {
 		})
 	}
 }
+
+func TestCopy(t *testing.T) {
+	type T int
+	v0, v1, v2, v3 := T(0), T(1), T(2), T(3)
+	s := []*T{&v0, &v1, &v2, &v3, nil}
+	e := Copy(s)
+	require.Equal(t, len(s), len(e))
+	for i := range s {
+		if s[i] == nil {
+			require.Nil(t, e[i])
+		} else {
+			require.Equal(t, *s[i], *e[i])
+			require.True(t, s[i] != e[i])
+		}
+	}
+}