planner: return the complete error info when Parallel Apply meets problem

pkg/planner/core/casetest/parallelapply/BUILD.bazel

@@ -0,0 +1,16 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_test")
+
+go_test(
+    name = "parallelapply_test",
+    timeout = "short",
+    srcs = [
+        "main_test.go",
+        "parallel_apply_test.go",
+    ],
+    flaky = True,
+    deps = [
+        "//pkg/testkit",
+        "//pkg/testkit/testsetup",
+        "@org_uber_go_goleak//:goleak",
+    ],
+)

pkg/planner/core/casetest/parallelapply/main_test.go

@@ -0,0 +1,36 @@
+// Copyright 2024 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package parallelapply
+
+import (
+	"testing"
+
+	"github.com/pingcap/tidb/pkg/testkit/testsetup"
+	"go.uber.org/goleak"
+)
+
+func TestMain(m *testing.M) {
+	testsetup.SetupForCommonTest()
+	opts := []goleak.Option{
+		goleak.IgnoreTopFunction("github.com/golang/glog.(*fileSink).flushDaemon"),
+		goleak.IgnoreTopFunction("github.com/bazelbuild/rules_go/go/tools/bzltestutil.RegisterTimeoutHandler.func1"),
+		goleak.IgnoreTopFunction("github.com/lestrrat-go/httprc.runFetchWorker"),
+		goleak.IgnoreTopFunction("go.etcd.io/etcd/client/pkg/v3/logutil.(*MergeLogger).outputLoop"),
+		goleak.IgnoreTopFunction("gopkg.in/natefinch/lumberjack%2ev2.(*Logger).millRun"),
+		goleak.IgnoreTopFunction("github.com/tikv/client-go/v2/txnkv/transaction.keepAlive"),
+		goleak.IgnoreTopFunction("go.opencensus.io/stats/view.(*worker).start"),
+	}
+	goleak.VerifyTestMain(m, opts...)
+}

pkg/planner/core/casetest/parallelapply/parallel_apply_test.go

@@ -0,0 +1,33 @@
+// Copyright 2024 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package parallelapply
+
+import (
+	"testing"
+
+	"github.com/pingcap/tidb/pkg/testkit"
+)
+
+func TestParallelApplyWarnning(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("create table t1 (a int, b int, c int);")
+	tk.MustExec("create table t2 (a int, b int, c int, key(a));")
+	tk.MustExec("create table t3(a int, b int, c int, key(a));")
+	tk.MustExec("set tidb_enable_parallel_apply=on;")
+	tk.MustQuery("select (select 1 from t2, t3 where t2.a=t3.a and t2.b > t1.b) from t1;")
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 Some apply operators can not be executed in parallel: *core.PhysicalIndexHashJoin doesn't support cloning"))
+}

pkg/planner/core/optimizer.go

@@ -1116,9 +1116,12 @@ func enableParallelApply(sctx sessionctx.Context, plan PhysicalPlan) PhysicalPla
 		if noOrder && supportClone {
 			apply.Concurrency = sctx.GetSessionVars().ExecutorConcurrency
 		} else {
-			sctx.GetSessionVars().StmtCtx.AppendWarning(errors.NewNoStackErrorf("Some apply operators can not be executed in parallel"))
+			if err != nil {
+				sctx.GetSessionVars().StmtCtx.AppendWarning(errors.NewNoStackErrorf("Some apply operators can not be executed in parallel: %v", err))
+			} else {
+				sctx.GetSessionVars().StmtCtx.AppendWarning(errors.NewNoStackError("Some apply operators can not be executed in parallel"))
+			}
 		}
-
 		// because of the limitation 3, we cannot parallelize Apply operators in this Apply's inner size,
 		// so we only invoke recursively for its outer child.
 		apply.SetChild(outerIdx, enableParallelApply(sctx, apply.Children()[outerIdx]))