planner: fix panic when the join key is scalarFunction

executor/explain_test.go

@@ -365,3 +365,24 @@ func (s *testSuite) TestExplainStatementsSummary(c *C) {
 	tk.MustQuery("desc select * from information_schema.statements_summary where digest in ('a','b','c')").Check(testutil.RowsWithSep(" ",
 		`MemTableScan_5 10000.00 root table:STATEMENTS_SUMMARY digests: ["a","b","c"]`))
 }
+
+func (s *testSuite) TestFix29401(c *C) {
+	tk := testkit.NewTestKitWithInit(c, s.store)
+	tk.MustExec("drop table if exists tt123;")
+	tk.MustExec(`CREATE TABLE tt123 (
+  id int(11) NOT NULL,
+  a bigint(20) DEFAULT NULL,
+  b char(20) DEFAULT NULL,
+  c datetime DEFAULT NULL,
+  d double DEFAULT NULL,
+  e json DEFAULT NULL,
+  f decimal(40,6) DEFAULT NULL,
+  PRIMARY KEY (id) /*T![clustered_index] CLUSTERED */,
+  KEY a (a),
+  KEY b (b),
+  KEY c (c),
+  KEY d (d),
+  KEY f (f)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;`)
+	tk.MustExec(" explain select /*+ inl_hash_join(t1) */ * from tt123 t1 join tt123 t2 on t1.b=t2.e;")
+}

planner/core/rule_predicate_push_down.go

@@ -292,6 +292,10 @@ func (p *LogicalProjection) appendExpr(expr expression.Expression) *expression.C
 	}
 	col.SetCoercibility(expr.Coercibility())
 	p.schema.Append(col)
+	// reset ParseToJSONFlag in order to keep the flag away from json column
+	if col.GetType().Tp == mysql.TypeJSON {
+		col.GetType().Flag &= ^mysql.ParseToJSONFlag
+	}
 	return col
 }