[#MDEV-7801] Unexpected syntax error in ALTER TABLE t1 ADD INDEX TYPE BTREE

USING and TYPE are supposed to be synonyms in the key algorithm type clause,
and both work fine in the following two scripts:

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a INT);

ALTER TABLE t1 ADD INDEX type USING BTREE (a);

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a INT);

ALTER TABLE t1 ADD INDEX type TYPE BTREE (a);

However, if I remove the index name (which is optional, according to the grammar), USING still works fine:

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a INT);

ALTER TABLE t1 ADD INDEX USING BTREE (a);

but TYPE fails:

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a INT);

ALTER TABLE t1 ADD INDEX TYPE BTREE (a);

It returns the following error:

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'BTREE (a)' at line 1

The problem is obviously in this piece of grammar in sql_yacc.yy:

key_def:

          normal_key_type opt_if_not_exists_opt_table_element_name

          key_alg '(' key_list ')'

          { Lex->option_list= NULL; }

          normal_key_options

            if (add_create_index (Lex, $1, $2, Lex->check_exists))

              MYSQL_YYABORT;

When it gets the word TYPE, it does no know if it is the index name, or the start of the key algorithm clause, such as "TYPE BTREE".

There are more parser related problems:

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a INT) ENGINE=HEAP;

CREATE INDEX i1 USING  HASH ON t1 (a) USING BTREE;

SHOW CREATE TABLE t1;

The above script ignores the first USING and returns:

+-------+---------------------------------------------------------------------------------------------------------------------+

| Table | Create Table                                                                                                        |

+-------+---------------------------------------------------------------------------------------------------------------------+

| t1    | CREATE TABLE `t1` (

  `a` int(11) DEFAULT NULL,

  KEY `i1` (`a`) USING BTREE

) ENGINE=MEMORY DEFAULT CHARSET=latin1 |

+-------+---------------------------------------------------------------------------------------------------------------------+

The expected behaviour would be to return an error telling about conflicting declarations.

[MDEV-7801] Unexpected syntax error in ALTER TABLE t1 ADD INDEX TYPE BTREE Created: 2015-03-18 Updated: 2019-10-04
Status:	Open
Project:	MariaDB Server
Component/s:	Data Definition - Alter Table
Affects Version/s:	5.1.67, 5.2.14, 5.3.12, 5.5, 10.0, 10.1, 10.3.4
Fix Version/s:	10.1

[MDEV-7801] Unexpected syntax error in ALTER TABLE t1 ADD INDEX TYPE BTREE Created: 2015-03-18 Updated: 2019-10-04