sql: fix statement bundle creation when memo isn't detached

When a memo is deemed not resuable we don't detach it from the factory
and this causes problems later when we execute SetIndexRecommendations
which resets the optimizer context which will reset the memo.  This
causes the schema.sql and opt*.txt files to be empty.

Fixes: #92920

Release note: None

pkg/sql/explain_bundle.go

@@ -36,6 +36,8 @@ import (
 	"github.com/cockroachdb/errors"
 )
 
+const noPlan = "no plan"
+
 // setExplainBundleResult sets the result of an EXPLAIN ANALYZE (DEBUG)
 // statement. warnings will be printed out as is in the CLI.
 //
@@ -242,9 +244,9 @@ func (b *stmtBundleBuilder) addStatement() {
 func (b *stmtBundleBuilder) addOptPlans() {
 	if b.plan.mem == nil || b.plan.mem.RootExpr() == nil {
 		// No optimizer plans; an error must have occurred during planning.
-		b.z.AddFile("opt.txt", "no plan")
-		b.z.AddFile("opt-v.txt", "no plan")
-		b.z.AddFile("opt-vv.txt", "no plan")
+		b.z.AddFile("opt.txt", noPlan)
+		b.z.AddFile("opt-v.txt", noPlan)
+		b.z.AddFile("opt-vv.txt", noPlan)
 		return
 	}
 

pkg/sql/explain_bundle_test.go

@@ -101,6 +101,19 @@ CREATE TABLE s.a (a INT PRIMARY KEY);`)
 		checkBundle(t, fmt.Sprintf("%+v", pqErr.Detail), "", nil, base, plans, "distsql.html")
 	})
 
+	// #92920 Make sure schema and opt files are created.
+	t.Run("memo-reset", func(t *testing.T) {
+		rows := r.QueryStr(t, "EXPLAIN ANALYZE (DEBUG) CREATE TABLE t (i int)")
+		checkBundle(t, fmt.Sprint(rows), "", func(name, contents string) error {
+			if name == "opt.txt" {
+				if contents == noPlan {
+					return errors.Errorf("opt.txt empty")
+				}
+			}
+			return nil
+		}, base, plans, "distsql.html vec.txt vec-v.txt")
+	})
+
 	// Verify that we can issue the statement with prepare (which can happen
 	// depending on the client).
 	t.Run("prepare", func(t *testing.T) {

pkg/sql/opt/norm/factory.go

@@ -166,6 +166,15 @@ func (f *Factory) DetachMemo() *memo.Memo {
 	return m
 }
 
+// ReleaseMemo is just like DetachMemo but it doesn't call Detach on the memo
+// preserving any statistics information for explain purposes (distinct, null
+// count etc).
+func (f *Factory) ReleaseMemo() *memo.Memo {
+	m := f.mem
+	f.mem = nil
+	return m
+}
+
 // DisableOptimizations disables all transformation rules. The unaltered input
 // expression tree becomes the output expression tree (because no transforms
 // are applied).

pkg/sql/plan_opt.go

@@ -593,7 +593,7 @@ func (opc *optPlanningCtx) buildExecMemo(ctx context.Context) (_ *memo.Memo, _ e
 		return memo, nil
 	}
 
-	return f.Memo(), nil
+	return f.ReleaseMemo(), nil
 }
 
 // runExecBuilder execbuilds a plan using the given factory and stores the