[#MDEV-10079] sql_yacc.yy: Remove non-parenthesized SELECT from table

The "table_ref" rule allows non-parenthesized SELECT query.
table_ref is used in derived_table_list and join_table.

Non-parenthesized SELECT query is OK in derived_table_list, which is used (among other things) to handle derived tables in FROM clause:

SELECT * FROM (SELECT * FROM t1);

But when table_ref is used in join_table, non-parenthesized SELECT should not be allowed:

join_table:

          table_ref normal_join table_ref

        | table_ref normal_join table_ref ON ...

        | table_ref normal_join table_ref USING ...

        | table_ref NATURAL inner_join table_factor

        | table_ref LEFT opt_outer JOIN_SYM table_ref ON ...

        | table_ref LEFT opt_outer JOIN_SYM table_factor USING

        | table_ref NATURAL LEFT opt_outer JOIN_SYM table_factor

        | table_ref RIGHT opt_outer JOIN_SYM table_ref ON ...

        | table_ref RIGHT opt_outer JOIN_SYM table_factor USING ...

        | table_ref NATURAL RIGHT opt_outer JOIN_SYM table_factor

Examples of bad queries:

SELECT * FROM (SELECT 1 NATURAL JOIN t2);  -- SELECT 1 on the left side of JOIN is incorrect

SELECT * FROM t1 NATURAL JOIN SELECT 1; -- SELECT on the right side of JOIN is incorrect

Currently bad queries are caught by extra code:

  MYSQL_YYABORT_UNLESS($1 && ($$=$4));

  $4->straight=$3;

  add_join_natural($1,$4,NULL,Select);

if (!sel->embedding || sel->end_nested_join(lex->thd))

  /* we are not in parentheses */

  my_parse_error(thd, ER_SYNTAX_ERROR);

    MYSQL_YYABORT;

Under terms of this task we'll disallow such queries syntactically, by moving non-parenthesized SELECT from table_ref to derived_table_list.
Unfortunately, it's not possible to remove the extra code at this stage, because it's used for some other purposes as well.

[MDEV-10079] sql_yacc.yy: Remove non-parenthesized SELECT from table_ref Created: 2016-05-17 Updated: 2016-05-17 Resolved: 2016-05-17
Status:	Closed
Project:	MariaDB Server
Component/s:	Parser
Fix Version/s:	10.2.1

[MDEV-10079] sql_yacc.yy: Remove non-parenthesized SELECT from table_ref Created: 2016-05-17 Updated: 2016-05-17 Resolved: 2016-05-17