executor: fix bad null error handling for insert statement when disab…

…ling the strict SQL mode (#10161)

executor/executor.go

@@ -1333,8 +1333,11 @@ func ResetContextOfStmt(ctx sessionctx.Context, s ast.StmtNode) (err error) {
 		sc.Priority = stmt.Priority
 	case *ast.InsertStmt:
 		sc.InInsertStmt = true
+		// For insert statement (not for update statement), disabling the StrictSQLMode
+		// should make TruncateAsWarning and DividedByZeroAsWarning,
+		// but should not make DupKeyAsWarning or BadNullAsWarning,
 		sc.DupKeyAsWarning = stmt.IgnoreErr
-		sc.BadNullAsWarning = !vars.StrictSQLMode || stmt.IgnoreErr
+		sc.BadNullAsWarning = stmt.IgnoreErr
 		sc.TruncateAsWarning = !vars.StrictSQLMode || stmt.IgnoreErr
 		sc.DividedByZeroAsWarning = !vars.StrictSQLMode || stmt.IgnoreErr
 		sc.AllowInvalidDate = vars.SQLMode.HasAllowInvalidDatesMode()

executor/executor_test.go

@@ -1767,8 +1767,15 @@ func (s *testSuite) TestSQLMode(c *C) {
 
 	tk.MustExec("set sql_mode = ''")
 	tk.MustExec("insert t values ()")
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1364 Field 'a' doesn't have a default value"))
+	_, err = tk.Exec("insert t values (null)")
+	c.Check(err, NotNil)
+	tk.MustExec("insert ignore t values (null)")
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1048 Column 'a' cannot be null"))
+	tk.MustExec("insert t select null")
+	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1048 Column 'a' cannot be null"))
 	tk.MustExec("insert t values (1000)")
-	tk.MustQuery("select * from t").Check(testkit.Rows("0", "127"))
+	tk.MustQuery("select * from t order by a").Check(testkit.Rows("0", "0", "0", "127"))
 
 	tk.MustExec("insert tdouble values (10.23)")
 	tk.MustQuery("select * from tdouble").Check(testkit.Rows("9.99"))

executor/insert_common.go

@@ -301,6 +301,10 @@ func (e *InsertValues) insertRowsFromSelect(ctx context.Context, exec func(ctx c
 	rows := make([][]types.Datum, 0, chk.Capacity())
 
 	sessVars := e.ctx.GetSessionVars()
+	if !sessVars.StrictSQLMode {
+		// If StrictSQLMode is disabled and it is a insert-select statement, it also handle BadNullAsWarning.
+		sessVars.StmtCtx.BadNullAsWarning = true
+	}
 	batchInsert := sessVars.BatchInsert && !sessVars.InTxn()
 	batchSize := sessVars.DMLBatchSize
 

executor/write_test.go

@@ -719,6 +719,11 @@ commit;`
 	tk.CheckLastMessage("")
 	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1048 Column 'f2' cannot be null"))
 	tk.MustQuery(`SELECT * FROM t1 order by f1;`).Check(testkit.Rows("1 0", "2 2"))
+
+	tk.MustExec(`SET sql_mode='';`)
+	_, err = tk.Exec(`INSERT t1 VALUES (1, 1) ON DUPLICATE KEY UPDATE f2 = null;`)
+	c.Assert(err, NotNil)
+	tk.MustQuery(`SELECT * FROM t1 order by f1;`).Check(testkit.Rows("1 0", "2 2"))
 }
 
 func (s *testSuite2) TestInsertIgnoreOnDup(c *C) {

table/column.go

@@ -426,11 +426,16 @@ func getColDefaultValueFromNil(ctx sessionctx.Context, col *model.ColumnInfo) (t
 	if col.IsGenerated() {
 		return types.Datum{}, nil
 	}
-	sc := ctx.GetSessionVars().StmtCtx
+	vars := ctx.GetSessionVars()
+	sc := vars.StmtCtx
 	if sc.BadNullAsWarning {
 		sc.AppendWarning(ErrColumnCantNull.GenWithStackByArgs(col.Name))
 		return GetZeroValue(col), nil
 	}
+	if !vars.StrictSQLMode {
+		sc.AppendWarning(ErrNoDefaultValue.GenWithStackByArgs(col.Name))
+		return GetZeroValue(col), nil
+	}
 	return types.Datum{}, ErrNoDefaultValue.GenWithStackByArgs(col.Name)
 }