opt: make max-stack opt tester option more reliable

The `max-stack` opt tester option now run the test command in a separate
goroutine. A fresh stack makes tests using this setting more reliable.

It also reverts the increase of `max-stack` of a test from cockroachdb#133241
because it is no longer necessary.

Release note: None

pkg/sql/opt/testutils/opttester/opt_tester.go

@@ -23,6 +23,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"testing"
 	"text/tabwriter"
 	"time"
@@ -566,6 +567,26 @@ func New(catalog cat.Catalog, sqlStr string) *OptTester {
 //   - max-stack: sets the maximum stack size for the goroutine that optimizes
 //     the query. See debug.SetMaxStack.
 func (ot *OptTester) RunCommand(tb testing.TB, d *datadriven.TestData) string {
+	if ot.Flags.MaxStackBytes > 0 {
+		originalMaxStack := debug.SetMaxStack(ot.Flags.MaxStackBytes)
+		defer debug.SetMaxStack(originalMaxStack)
+		// Spawn a separate goroutine. A fresh stack makes tests using this
+		// setting more reliable.
+		var wg sync.WaitGroup
+		wg.Add(1)
+		var res string
+		go func() {
+			defer wg.Done()
+			res = ot.runCommandInternal(tb, d)
+		}()
+		wg.Wait()
+		return res
+	} else {
+		return ot.runCommandInternal(tb, d)
+	}
+}
+
+func (ot *OptTester) runCommandInternal(tb testing.TB, d *datadriven.TestData) string {
 	// Allow testcases to override the flags.
 	for _, a := range d.CmdArgs {
 		if err := ot.Flags.Set(a); err != nil {
@@ -588,11 +609,6 @@ func (ot *OptTester) RunCommand(tb testing.TB, d *datadriven.TestData) string {
 	ot.evalCtx.Placeholders = nil
 	ot.evalCtx.TxnIsoLevel = ot.Flags.TxnIsoLevel
 
-	if ot.Flags.MaxStackBytes > 0 {
-		originalMaxStack := debug.SetMaxStack(ot.Flags.MaxStackBytes)
-		defer debug.SetMaxStack(originalMaxStack)
-	}
-
 	switch d.Cmd {
 	case "exec-ddl":
 		testCatalog, ok := ot.catalog.(*testcat.Catalog)

pkg/sql/opt/xform/testdata/rules/select

@@ -2820,7 +2820,7 @@ CREATE TABLE t132669 (
 # unnecessary recursion to trigger a stack overflow without having to make the
 # `IN` list below huge - triggering a stack overflow with Go's default max stack
 # size requires a list of ~1.6 million elements.
-opt max-stack=125KB format=hide-all
+opt max-stack=50KB format=hide-all
 SELECT * FROM t132669
 WHERE a IN (
     1,  2,  3,  4,  5,  6,  7, 8, 9, 10,