fix(prqlc): allow prqlc compile | duckdb

[eitsupi]

Fix comments displayed in interactive mode and make interactive mode output valid SQL output.
(It also fixes #2569)

This PR allows PRQL to be executed interactively by piping prqlc compile to duckdb, sqlite3, etc.

I have also added a note to the prqlc README on how to use the prqlc compile command, which I believe is the minimum required to try prqlc.
And this README also has been changed to appear in the book.

[eitsupi]

(By the way, I think a combination of prqlc and the DuckDB CLI seems more Unix-like and a better path than using the prql-query CLI with DuckDB built in......) (Related to PRQL/prql-query#22)

prqlc compile --target sql.duckdb | duckdb --json >output.json

[max-sixty]

Excellent, thanks a lot!

I added a couple of comments & suggestions, but otherwise good to go

[max-sixty]

Hmmm, this doesn't work so well on mine — does it for you?

I think maybe we write the Ctrl-d to stdout?

prqlc compile | duckdb
from `penguins.csv`
take 3
Error: near line 1: Parser Error: syntax error at or near "Enter"
LINE 1: Enter PRQL, then ctrl-d:
        ^

(Is there a way of retaining the query? I worry this approach is OK but loses the query on each run. But it's still reasonable to show the example)

[eitsupi]

It seems that the prqlc you are using was not built from this PR. (the prompt message is different)

[eitsupi]

Is there a way of retaining the query?

I believe the query will remain visible in the terminal as shown in this README, and I have verified that it works with bash and fish on Linux and PowerShell on Windows.

[max-sixty]

It seems that the prqlc you are using was not built from this PR. (the prompt message is different)

Sorry, you're correct, apologies

[max-sixty]

I believe the query will remain visible in the terminal as shown in this README, and I have verified that it works with bash and fish on Linux and PowerShell on Windows.

Yes!

A total aside — something @snth and I discussed on the dev call was building a TUI, similar to the playground, where typing a query would pipe through to duckdb on each keystroke, could be a good way of exploring a dataset from the terminal

[max-sixty]

Suggested change

	println!("# Enter PRQL, then press ctrl-d or ctrl-z (windows) to compile:\n");
	eprintln!("# Enter PRQL, then press ctrl-d or ctrl-z (windows) to compile:\n");

...I think this will solve the issue above

[max-sixty]

FYI we could use this approach to print the correct string:

prql/prql-compiler/prqlc/src/cli.rs

Line 508 in e32c586

#[cfg(not(unix))]

[max-sixty]

(By the way, I think a combination of prqlc and the DuckDB CLI seems more Unix-like and a better path than using the prql-query CLI with DuckDB built in......)

I do think this is a great pattern, agree.

[aljazerzen]

Looks good.

[eitsupi]

Thanks for your reviews!

I think I have addressed most of the comments, so I will merge this.
If additional updates are needed, I will open another PR.