tracking: sql variable features

[sundy-li]

Summary

• basic SQL variable support in session level feat(query): add sql variable support #16134
• IDENTIFIER function support SQL variable IDENTIFIER($my_table_name), replace ident in NameResolutionContext feat(query): add identifier function from session variable #16264
• support serde/deserde variables to HTTP response and apply variables changes during session start (work like settings)
• show variables #16274
• drivers support SQL variables (databend-go, bendsql, databend-jdbc)
• docs

[TCeason]

Got it

[TCeason]

Add config or setting about variable quota.

Personally, I'm more biased towards setting.

Now we has user role quota config. But user and role is a global tenant level object. But var just a session level object.

[sundy-li]

Add config or setting about variable quota.

Personally, I'm more biased towards setting.

Now we has user role quota config. But user and role is a global tenant level object. But var just a session level object.

No need now.

[sundy-li]

cc @soyeric128 Let's add documents about sql variables.