Optimize ContentPath#pathAsText

[dorukguner]

This pr optimizes calls to ContentPath#pathAsText through the following changes:

• When at the root we return the provided string directly
• When called on a sibling or child field the previously built path is maintained to prevent appending the same top-level fields again

The case in which fields that have been previously added to the path are removed is handled in ContentPath#remove by clearing the existing StringBuilder.

Tests for ContentPath#pathAsText have been added in a separate commit to the optimization to allow for easy validation that the tests are correct.

Addresses #94544

[cla-checker-service]

💚 CLA has been signed

[elasticsearchmachine]

Pinging @elastic/es-search (Team:Search)

[cbuescher]

Hi @dorukguner, sorry for the delay in getting to this and thanks for picking it up.
I like the solution and the tests are great. Since we have tests now I would like to go a step further and optimize your solution even a bit more. I left a few suggestions for that, let me know what you think.

[dorukguner]

Hi @cbuescher, thanks for the feedback.

I've merged the extra test cases I had into the new main test class and I've also optimised ContentPath a little further.

I realised we didn't need both an array of strings for the path and a string builder. We can have just a string builder while keeping track of the indexes in which the delimiters were added, and using the add and remove methods to modify the string builder directly. This has removed the need for any loops and any extra indexes.

Please let me know what you think about the new optimisations, I'm open to any other suggestions you may have.

[cbuescher]

@dorukguner thanks a lot, I think the idea of just keeping one datastructure for the whole path and keeping around the pointers to the parts is great and the tests are also covering this nicely. I left two small comments but will prepare this PR for testing and merging while you address those.

[cbuescher]

Just running a check before the final changes to see if this breaks anything else.

@elasticsmachine test this please

[cbuescher]

@dorukguner could you also run ./gradlew :server:spotlessApply to apply our formatting rules to the modified classes?

[cbuescher]

Thanks for the update, LGTM. Will need to run full test suite before merging.

[cbuescher]

@elasticmachine test this please

[cbuescher]

@elasticmachine test this please

[cbuescher]

@elasticmachine update branch

[cbuescher]

@elasticmachine test this please

[cbuescher]

@dorukguner huzzah, all passed. Thanks for the change and the iterations, merged to main branch now. I think this is a great change that makes using this class a lot less wasteful.