parser: compatibility enhancement for SELECT ... INTO syntax

[bb7133]

Enhancement

Now TiDB does not support the following SELECT ... INTO syntax:

tidb> select * into outfile 'abc' from test.t;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your TiDB version for the right syntax to use line 1 column 32 near "from test.t"

In which INTO clause appears before FROM clause, as described in MySQL manual:

SELECT
[ALL | DISTINCT | DISTINCTROW ]
[HIGH_PRIORITY]
[STRAIGHT_JOIN]
[SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT]
[SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS]
select_expr [, select_expr] ...
[into_option]
[FROM table_references
[PARTITION partition_list]]
[WHERE where_condition]
[GROUP BY {col_name | expr | position}
[ASC | DESC], ... [WITH ROLLUP]]
[HAVING where_condition]
[ORDER BY {col_name | expr | position}
[ASC | DESC], ...]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]
[PROCEDURE procedure_name(argument_list)]
[into_option]
[FOR UPDATE | LOCK IN SHARE MODE]

into_option: {
INTO OUTFILE 'file_name'
[CHARACTER SET charset_name]
export_options
| INTO DUMPFILE 'file_name'
| INTO var_name [, var_name] ...
}

...

The INTO clause, if present, can appear in any position indicated by the syntax description, but within a given statement can appear only once, not in multiple positions...

To improve the compatibility, we need to update parser.y file and try to update the declaration of SelectStmt:

tidb/parser/parser.y

Line 8646 in fdf335e

SelectStmt:

Some tips:

• Please notice that the change might be trivial or non-trivial because the parsing code of TiDB is not the same as MySQL.
• In MySQL 8.0, the INTO clause is allowed to appear after FOR UPDATE clause, we could also consider supporting it as well(nice to have).

[mjonss]

@bb7133 do you only mean that the parser should correctly parse this, and then we can fail with a better error message?Since I don't think we should fully support into outfile since TiDB is a cluster and you may not be aware of which TiDB SQL node you were using.

[bb7133]

@mjonss I think we should support INTO in different positions(just like MySQL) without any other funcational enhancement, since some 3rd-party tools use it in this way.

Since I don't think we should fully support into outfile

Yes, I agree with it.