feat(planner): support settings set sql_dialect

[b41sh]

I hereby agree to the terms of the CLA available at: https://databend.rs/dev/policies/cla/

Summary

Support settings set sql_dialect

Fixes #7131

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Updated
databend	✅ Ready (Inspect)	Visit Preview	Aug 18, 2022 at 4:01PM (UTC)

[sundy-li]

Need a test file in logictest.

For example:

set sql_dialect = 'xxxx';

select "33";

[leiysky]

@b41sh

We should provide a default SQL dialect for databend.

Before persisting any of the SQL query, the SQL text must be normalized into default dialect. Otherwise we will encounter bugs if user is creating a view with MySQL dialect but query with default dialect.

For example, user is creating a view with create view v as select "A" from t in MySQL dialect, then the token "A" is ambigious, which is impossible to be fixed.

[b41sh]

@b41sh

We should provide a default SQL dialect for databend.

Before persisting any of the SQL query, the SQL text must be normalized into default dialect. Otherwise we will encounter bugs if user is creating a view with MySQL dialect but query with default dialect.

For example, user is creating a view with create view v as select "A" from t in MySQL dialect, then the token "A" is ambigious, which is impossible to be fixed.

the default SQL dialect is PostgreSQL, can we rewrite the view query to PostgreSQL?

[b41sh]

@leiysky the subquery of view is formatted as PostgreSQL dialect. When querying, whether it is MySQL or PostgreSQL dialect, we can get the correct results.