parser: set `UnionStmt` and `ShowStmt` as readonly (pingcap#755) (pin…

…gcap#756)

* add UnionStmt and ShowStmt as readonly

* fix UnionStmt

refine table optimizer hint and make it more generic (pingcap#747)

* refine table optimizer hint and make it more generic

Signed-off-by: Lonng <heng@lonng.org>

* implement the restore

Signed-off-by: Lonng <heng@lonng.org>

* address comment

Signed-off-by: Lonng <heng@lonng.org>

* address comment

Signed-off-by: Lonng <heng@lonng.org>

* fix typo

Signed-off-by: Lonng <heng@lonng.org>

parser: add Reload and File privileges (pingcap#708)

parser : add invalid auto increment and offset error (pingcap#707) (p…

…ingcap#712)

parser : add invalid auto increment and offset error (pingcap#707) (p…

…ingcap#712)

merge release 3.0 to release 3.1 (pingcap#710)

support require clauses in `grant` stmt (pingcap#666) (pingcap#698)

add auto_random error definitions (pingcap#696)

mysql: add foreign key error (pingcap#675) (pingcap#695)

Fix compatibility for `OnUpdate`, `OnDelete` and other clauses (pingc…

…ap#331, pingcap#392, pingcap#393) (pingcap#642) (pingcap#647)