Fix CREATE INDEX .. VISIBLE/INVISIBLE syntax

[zhenghaoz]

What problem does this PR solve?

Fix CREATE INDEX .. VISIBLE/INVISIBLE syntax

Issue: #478

MySQL Syntax:

CREATE [UNIQUE | FULLTEXT | SPATIAL] INDEX index_name
...
index_option:
....
   | {VISIBLE | INVISIBLE}

Bad SQL Case:

CREATE INDEX idx ON t ( a ) VISIBLE
CREATE INDEX idx ON t ( a ) INVISIBLE
CREATE INDEX idx ON t ( a ) USING HASH VISIBLE
CREATE INDEX idx ON t ( a ) USING HASH INVISIBLE
CREATE INDEX idx ON t ( a ) INVISIBLE VISIBLE
CREATE INDEX idx ON t ( a ) VISIBLE INVISIBLE

Check List

Tests

• Unit test

PS:

Since the default option is visible, VISIBLE won't be restored.

• VISIBLE, INVISIBLE

Specify index visibility. Indexes are visible by default. An invisible index is not used by the optimizer. Specification of index visibility applies to indexes other than primary keys (either explicit or implicit). For more information, see Section 8.3.12, “Invisible Indexes”.

[codecov]

Codecov Report

Merging #518 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #518      +/-   ##
==========================================
+ Coverage   71.67%   71.68%   +0.01%     
==========================================
  Files          32       32              
  Lines        7752     7756       +4     
==========================================
+ Hits         5556     5560       +4     
  Misses       1671     1671              
  Partials      525      525

Impacted Files	Coverage Δ
parser.go	70.58% <ø> (ø)	⬆️
misc.go	96.49% <ø> (ø)	⬆️
ast/ddl.go	80.27% <100%> (+0.04%)	⬆️

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[kennytm]

LGTM

[zier-one]

LGTM

[zier-one]

resolve conflicts please