Let empty queries export everything

[dominiklohmann]

📔 Description

This changes the empty query, i.e., either a non-provided query argument or an empty string as the query argument, to export everything. Under the hood this is implemented by transforming empty queries into a query that parses everything, namely #type != "this expression matches everything".

📝 Checklist

• All user-facing changes have changelog entries.
• The changes are reflected on docs.tenzir.com/vast, if necessary.
• The PR description contains instructions for the reviewer, if necessary.

🎯 Review Instructions

Try it out.

[mavam]

Why do you modify the expression parser for this? If the calling context provides the empty string, you can still fill in the somewhat arbitrary expression.

[dominiklohmann]

Why do you modify the expression parser for this? If the calling context provides the empty string, you can still fill in the somewhat arbitrary expression.

Because that requires touching four pieces of code instead of one, which is much less maintainable. Actually disregard that, I can just do the transformation in read_query. Particularly bad case of the Mondays.

[lava]

Looks simple enough, and I've tested locally that it works as expected.

It does a bit more than what was discussed in the story; we may want to reconsider if we want to restrict this feature to export since for expose and pivot it is a bit unintuitive, and for vast count a user may expect a more performant implementation for the operation of counting the number of items in the database.