Add fuzzer based on honggfuzz

[PsiACE]

Also see: #211

[BohuTANG]

Hi, @Dandandan @andygrove

With this patch, we can easily to run the fuzz tool for sqlparser-rs and find more fuzz issues, great for robustness.
In the future we can make a CI to run it (limited time, i.e 10 minutes).

[coveralls]

Pull Request Test Coverage Report for Build 901777498

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 21 unchanged lines in 6 files lost coverage.
• Overall coverage increased (+0.1%) to 90.17%

---

Files with Coverage Reduction	New Missed Lines	%
src/ast/data_type.rs	1	75.0%
src/ast/ddl.rs	2	80.18%
src/ast/query.rs	2	86.6%
src/parser.rs	4	85.89%
src/tokenizer.rs	4	91.18%
src/ast/mod.rs	8	70.6%

Totals
Change from base Build 676410191:	0.1%
Covered Lines:	5467
Relevant Lines:	6063

---

💛 - Coveralls

[alamb]

Sorry for the delay in review. I am trying to pitch in and help out now to clear the backlog.

This is very cool @PsiACE and @BohuTANG -- thank you. It is cool that it seems you have found a bug with this fuzzer already.

My biggest question is about the input -- does the fuzzer simply check against random inputs or does it somehow know how to randomly make sql statements?

[alamb]

Is it correct that this is a real bug that was found/fixed with the fuzzer?

[PsiACE]

no, just make clippy happy

[alamb]

This is pretty cool. Where does the data come from? Is it just random strings? Or does this somehow know how to make valid sql statements?

[alamb]

I see some related comments here: #211 (comment)

[PsiACE]

For now it is some random bytes, but can be used to find bugs. Optimization can be continued later, refer to: https://www.cockroachlabs.com/blog/sqlsmith-randomized-sql-testing/

[alamb]

In a past project, we had a harness that could generate random SQL queries and it found many bugs -- such tests are a wonderful way to help database software mature

[alamb]

Filed apache/datafusion#913 for DataFusion. Thanks for the pointer @PsiACE

[alamb]

I think it is cool and having initial fuzzing, even if just random strings to start, is a good first step.

[houqp]

This is pretty cool. Looking forward to the day when we could have sql syntax specific fuzzer :)