SOLR-18197: Add root document query shortcut support to NestPathField

[abumarjikar]

https://issues.apache.org/jira/browse/SOLR-18197

Description

This pull request introduces a quick and intuitive shortcut to query root documents within hierarchical/nested data structures using the NestPathField. Currently, finding root-level documents (which do not have a nested path defined) requires a more verbose or explicit query syntax. This change provides a cleaner "ease of use" developer experience when dealing with nested child documents.

Solution

When a query is made against this field with an empty value, a null value, or a root slash ("/"), it automatically constructs and returns a BooleanQuery that targets only top-level root documents. It accomplishes this by matching all documents and explicitly excluding any documents where the nested path field exists:

MUST: MatchAllDocsQuery

MUST_NOT: ExistenceQuery (for the NestPathField)

For all other standard path inputs, it safely falls back to the default super.getFieldQuery(...) behavior.

Tests

Please describe the tests you've developed or run to confirm this patch implements the feature or solves the problem.

Checklist

Please review the following and check all that apply:

• I have reviewed the guidelines for How to Contribute and my code conforms to the standards described there to the best of my ability.
• I have created a Jira issue and added the issue ID to my pull request title.
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• I have developed this patch against the main branch.
• I have run ./gradlew check.
• I have added tests for my changes.
• I have added documentation for the Reference Guide
• I have added a changelog entry for my change

[dsmiley]

Thanks. Looking to see this used widespread in code & docs. The goal is to ensure no user sees that ugly/confusing syntax that was previously necessary.

[dsmiley]

still definitely looking for the application of this in the codebase + doc updates

[dsmiley]

That change has a different underlying query & semantic effect. Formerly it found all docs separate from that parent path, thus matched not only the root doc but also /aa and /ff if that exists, say. You changed it to only match documents at /aa exactly.

[dsmiley]

again, these are not equivalent

[dsmiley]

more to do... not ready for my re-review

[dsmiley]

Audit usages of org.apache.solr.schema.IndexSchema#NEST_PATH_FIELD_NAME and you will find code that can be updated.

[abumarjikar]

@dsmiley I audited the usage of IndexSchema#NEST_PATH_FIELD_NAME as suggested, and here is where I updated the logic (and where I intentionally left it out):

1. Updated buildAllParentsFilterFromPath: > I replaced the manual, verbose BooleanQuery builder block for the root path (/ or empty) by directly delegating to my new nestPathField.getType().getFieldQuery(this, nestPathField, "/") logic. This completely removes the redundant manual construction of the "match all minus existence" pattern and unifies it under the new shortcut.

2. Left wrapWithParentPathConstraint mostly as-is: > I evaluated using the new getFieldQuery here, but for the non-MatchAllDocsQuery path, forcing the new method would have required nesting a structured BooleanQuery ([+MatchAllDocsQuery, -ExistenceQuery]) inside a FILTER or MUST clause. This would have introduced an unnecessary extra layer to Lucene's internal query tree structure. Keeping the flat .add(newNestPathExistsQuery(), Occur.MUST_NOT) here keeps the execution path flat and fast, matching Lucene's design patterns perfectly.