[Sqlalchemy-tickets] Issue #3867: MySQL table definition parser warns about valid key definition (zzzeek/sqlalchemy)

[Lele L. <iss...@bi...>]

New issue 3867: MySQL table definition parser warns about valid key definition
https://bitbucket.org/zzzeek/sqlalchemy/issues/3867/mysql-table-definition-parser-warns-about

Lele Long:

I am using mysql  5.6.16-log, and SA warns as following:
```
/local/lib/python2.7/site-packages/sqlalchemy/dialects/mysql/reflection.py:56: SAWarning: Unknown schema content: u"  KEY `tbl_idx_pk` (`zip_code`,`shop_code`) USING BTREE COMMENT '(null)',"
  util.warn("Unknown schema content: %r" % line)

```
Code below demonstrates the problem, I have also found no such test case in mysql/test_reflection.py RawReflectionTest test_key_reflection
```
>>> from sqlalchemy.dialects.mysql import reflection
>>> from sqlalchemy.dialects.mysql import base as mysql
>>> dialect = mysql.dialect()
>>> parser = reflection.MySQLTableDefinitionParser(dialect, dialect.identifier_preparer)
>>> regex = parser._re_key
>>> assert regex.match("  PRIMARY KEY (`id`) USING BTREE KEY_BLOCK_SIZE 16,")
>>> assert regex.match("  PRIMARY KEY (`id`) USING BTREE COMMENT '(null)',")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AssertionError
>>> 
```

I would suggest adding comment to the regexp for key definition(_re_key) .