SOLR-18314: update both DisMax and eDisMax parsers to skip phrase ana…

[ispringer]

…lysis entirely for single-term queries, since a one-word phrase is semantically meaningless

https://issues.apache.org/jira/browse/SOLR-18314

Description

Both DisMax and eDisMax parsers should skip phrase analysis entirely for single-term queries, since a one-word phrase is semantically meaningless.

Solution

(coded by Claude Sonnet 4.6)

DisMax (DisMaxQParser.java:230-232): Added an early return null when the stripped query is blank or contains no whitespace (single term). This avoids wrapping a lone token in quotes and running it through the phrase parser for no benefit.

eDisMax (ExtendedDismaxQParser.java:633): Added if (shingleSize < 2) return; after the pf shingle size is resolved from 0 to clauses.size(). This short-circuits before constructing a query string, instantiating a parser, and parsing — all of which was previously done only to be discarded by minClauseSize=2 downstream.

Tests

Ran the tests for both query parsers:

  ./gradlew :solr:core:test --tests "org.apache.solr.search.TestExtendedDismaxParser" --tests
  "org.apache.solr.DisMaxRequestHandlerTest"

Result: 41 tests passed (38 from TestExtendedDismaxParser, 3 from DisMaxRequestHandlerTest)

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