load: fix load data with non-utf8 will succeed (#26054) (#26142)

executor/executor.go

@@ -1701,7 +1701,10 @@ func ResetContextOfStmt(ctx sessionctx.Context, s ast.StmtNode) (err error) {
 	case *ast.LoadDataStmt:
 		sc.DupKeyAsWarning = true
 		sc.BadNullAsWarning = true
-		sc.TruncateAsWarning = !vars.StrictSQLMode
+		// With IGNORE or LOCAL, data-interpretation errors become warnings and the load operation continues,
+		// even if the SQL mode is restrictive. For details: https://dev.mysql.com/doc/refman/8.0/en/load-data.html
+		// TODO: since TiDB only support the LOCAL by now, so the TruncateAsWarning are always true here.
+		sc.TruncateAsWarning = true
 		sc.InLoadDataStmt = true
 	case *ast.SelectStmt:
 		sc.InSelectStmt = true