txn: fix the warnings in pipelined dml (#51867)

ref #50215

Makefile

@@ -628,6 +628,13 @@ bazel_importintotest4: failpoint-enable bazel_ci_simple_prepare
 		-- //tests/realtikvtest/importintotest4/...
 	./build/jenkins_collect_coverage.sh
 
+# on timeout, bazel won't print log sometimes, so we use --test_output=all to print log always
+bazel_pipelineddmltest: failpoint-enable bazel_ci_simple_prepare
+	bazel $(BAZEL_GLOBAL_CONFIG) coverage $(BAZEL_CMD_CONFIG) $(BAZEL_INSTRUMENTATION_FILTER) --test_output=all --test_arg=-with-real-tikv --define gotags=deadlock,intest \
+	--@io_bazel_rules_go//go/config:cover_format=go_cover \
+		-- //tests/realtikvtest/pipelineddmltest/...
+	./build/jenkins_collect_coverage.sh
+
 bazel_lint: bazel_prepare
 	bazel build //... --//build:with_nogo_flag=true
 

pkg/session/session.go

@@ -4367,18 +4367,14 @@ func (s *session) usePipelinedDmlOrWarn() bool {
 			stmtCtx.AppendWarning(errors.New("Pipelined DML can not be used on sequence. Fallback to standard mode"))
 			return false
 		}
-		if len(tbl.Meta().ForeignKeys) > 0 && vars.ForeignKeyChecks {
+		if vars.ForeignKeyChecks && (len(tbl.Meta().ForeignKeys) > 0 || len(is.GetTableReferredForeignKeys(t.DB, t.Table)) > 0) {
 			stmtCtx.AppendWarning(
 				errors.New(
 					"Pipelined DML can not be used on table with foreign keys when foreign_key_checks = ON. Fallback to standard mode",
 				),
 			)
 			return false
 		}
-		referredFKs := is.GetTableReferredForeignKeys(t.DB, t.Table)
-		if len(referredFKs) > 0 {
-			return false
-		}
 		if tbl.Meta().TempTableType != model.TempTableNone {
 			stmtCtx.AppendWarning(
 				errors.New(

tests/realtikvtest/pipelineddmltest/pipelineddml_test.go

@@ -198,7 +198,8 @@ func TestPipelinedDMLNegative(t *testing.T) {
 	// for explain and explain analyze
 	tk.Session().GetSessionVars().BinlogClient = binloginfo.MockPumpsClient(&testkit.MockPumpClient{})
 	tk.MustExec("explain insert into t values(8, 8)")
-	tk.MustQuery("show warnings").CheckContain("Pipelined DML can not be used with Binlog: BinlogClient != nil. Fallback to standard mode")
+	// explain is read-only, so it doesn't warn.
+	tk.MustQuery("show warnings").Check(testkit.Rows())
 	tk.MustExec("explain analyze insert into t values(9, 9)")
 	tk.MustQuery("show warnings").CheckContain("Pipelined DML can not be used with Binlog: BinlogClient != nil. Fallback to standard mode")
 	tk.Session().GetSessionVars().BinlogClient = nil