Add Clickhouse support

[bojdell]

What do you want to change?

I've enjoyed using sqlc with postgres. However, I'm starting to do more work with Clickhouse and it would be great to also use sqlc there. I imagine this is a similar ask to #161 for sqlite and the core work required is integrating a query parser for ClickHouse. I don't have much experience in this area, but here is some potentially related content that may be helpful:

• ClickHouse SQL formal grammar or parser implementation ClickHouse/ClickHouse#7595
• ANTLR4 Grammar for ClickHouse and new parser ClickHouse/ClickHouse#11298

What database engines need to be changed?

No response

What programming language backends need to be changed?

No response

[bojdell]

@kyleconroy was there an outcome of the triaging?

[bojdell]

An alternate solution that's likely easier to implement is to add an argument to bypass schema validation - aka allow query generation without statically checking the queries against the schema and let the user rely on test codepaths to ensure correctness of the logic. Obviously using the argument would sacrifice safety but gain flexibility, enabling support for any ANSI SQL driver. Thoughts?

[cqhung1412]

Hi, @kyleconroy I'd like to ask if there is any progress on this.

[nexovec]

Are you guys considering this?

[matthewshirley]

I was also curious, but I don't think it is possible with the provided ANTLR4, as the output for Go is unusable:

• antlr golang generation error ClickHouse/ClickHouse#31650
  • Go visitor pattern antlr/antlr4#3299

Support was also dropped for the ANTLR4 files:

• Remove experimental ANTLR parser ClickHouse/ClickHouse#25942

Seems that a similar pattern to Postgres could be used with this clickhouse-sql-parser (https://github.com/AfterShip/clickhouse-sql-parser).

[w0rp]

I'm very much interested in having this as a feature, as I'd like to use this library to build tools that use ClickHouse as the only SQL-like database.

[1saifj]

Sqlc supporting Clickhouse is a big addition!.