Add a version() UDF

[samuelcolvin]

Which issue does this PR close?

Closes #12424

Rationale for this change

Pretty self explanatory — it's use to know what version of a database you're using.

What changes are included in this PR?

Adds a version() UDF.

Usage:

cargo run --manifest-path datafusion-cli/Cargo.toml

select version();
+--------------------------------------------+
| version()                                  |
+--------------------------------------------+
| Apache DataFusion 41.0.0, aarch64 on macos |
+--------------------------------------------+
1 row(s) fetched. 
Elapsed 0.018 seconds.

I'd like to add:

• Rustc version, but that would require a build script or another dependency
• Arrow-rs version, but would require a new export from arrow-rs, equivalent to datafusion::DATAFUSION_VERSION

Are these changes tested?

yes

Are there any user-facing changes?

Just one new UDF.

[alamb]

Thank you @samuelcolvin -- this looks very useful.

Can we please also add an entry in the documentation about this function: https://datafusion.apache.org/user-guide/sql/scalar_functions.html#other-functions

It would be nice if we could auto generate this documentation so we don't have to remember to add this type of documentation each time. I will write up a ticket explaining this

[alamb]

It would be nice if we could auto generate this documentation so we don't have to remember to add this type of documentation each time. I will write up a ticket explaining this

I filed #12432 to track this idea

[alamb]

I also think we should add a basic test to https://github.com/apache/datafusion/blob/main/datafusion/sqllogictest/test_files/information_schema.slt

(this file has to be updated on every version bump anyways so adding a test there will not increase the release burden)

[samuelcolvin]

Thank you @samuelcolvin -- this looks very useful.

Can we please also add an entry in the documentation about this function: https://datafusion.apache.org/user-guide/sql/scalar_functions.html#other-functions

It would be nice if we could auto generate this documentation so we don't have to remember to add this type of documentation each time. I will write up a ticket explaining this

done

[samuelcolvin]

note! this will go out of date very quickly, do we care?

[alamb]

I don't think it matters if the doc example doesn't reflect the current version

[Weijun-H]

Very useful feature! Thanks @samuelcolvin 👍

[alamb]

I also think we should add a basic test to https://github.com/apache/datafusion/blob/main/datafusion/sqllogictest/test_files/information_schema.slt

(this file has to be updated on every version bump anyways so adding a test there will not increase the release burden)

Since the function has the architecture in its output too, I don't think there is a way to cover it with tests in slt that wouldn't fail on some platforms. We would have to do it via rust tests where we could #cfg( on the target os.

I think it is ok to merge as is and I will make a PR shortly to add a test.

[alamb]

Thanks again @samuelcolvin and @Weijun-H

[alamb]

Test PR: #12441