Add support for distinct in multi search federation

[aznszn]

Pull Request

Related issue

Fixes #777

What does this PR do?

• Added distinct as a federation parameter

PR checklist

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• Did you use any AI tool while implementing this PR (code, tests, docs, etc.)? If yes, disclose it in the PR description and describe what it was used for. AI usage is allowed when it is disclosed.

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Summary by CodeRabbit

Release Notes

• New Features

  • Federated multi-search operations now support distinct parameters, enabling advanced deduplication and result filtering across multiple indexes. Users can specify distinct field values to optimize and control their result sets.

• Tests

  • Added integration test for federated multi-search with distinct parameter support, validating correct behavior and result aggregation across multiple indexes.

[coderabbitai]

📝 Walkthrough

Walkthrough

Added an optional distinct field to FederationOptions struct to support distinct value computation in federated multi-search requests. Includes an integration test validating the distinct parameter reduces hits to expected count.

Changes

Cohort / File(s)	Summary
Federated Search Distinct Support src/search.rs	Extended FederationOptions with optional distinct: Option<String> field; added integration test test_federated_multi_search_with_distinct to validate distinct filtering behavior in federated multi-search context.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A whisper through the federated streams,
Distinct at last—no more scattered dreams!
With Option<String> so clean and bright,
The search results merge just right. ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately and concisely summarizes the main change: adding distinct support for federated multi-search operations.
Linked Issues check	✅ Passed	The pull request successfully implements both objectives from issue #777: adds optional distinct field to FederationOptions and includes test coverage for federated search with distinct.
Out of Scope Changes check	✅ Passed	All changes are directly related to the linked issue #777 requirements; no out-of-scope modifications detected.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

🧹 Nitpick comments (1)

src/search.rs (1)

2406-2424: Strengthen this test to validate global distinct across merged queries.

At Line 2411-Line 2415, the test uses a single query, so it doesn’t really prove deduplication across federated merged results. Consider adding two queries and asserting uniqueness of kind in the merged hits.

Proposed test hardening

 #[meilisearch_test]
 async fn test_federated_multi_search_with_distinct(
     client: Client,
     index: Index,
 ) -> Result<(), Error> {
     setup_test_index(&client, &index).await?;
-    let search_query = SearchQuery::new(&index).build();
+    let search_query_text = SearchQuery::new(&index).with_query("Lorem").build();
+    let search_query_title = SearchQuery::new(&index).with_query("Harry").build();

     let mut multi_search = client.multi_search();
-    multi_search.with_search_query(search_query);
+    multi_search.with_search_query(search_query_text);
+    multi_search.with_search_query(search_query_title);

     let federated_multi_search = multi_search.with_federation(FederationOptions {
         distinct: Some("kind".to_string()),
         ..Default::default()
     });

     let response = federated_multi_search.execute::<Document>().await.unwrap();

     assert_eq!(response.hits.len(), 2);
+    let distinct_kinds = response
+        .hits
+        .iter()
+        .map(|hit| hit.result.kind.as_str())
+        .collect::<std::collections::HashSet<_>>();
+    assert_eq!(distinct_kinds.len(), response.hits.len());

     Ok(())
 }

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@src/search.rs` around lines 2406 - 2424, The test function
test_federated_multi_search_with_distinct currently only adds one SearchQuery,
so it doesn't validate global deduplication across merged federated results;
update the test to add two different SearchQuery instances to the multi_search
(e.g., call multi_search.with_search_query(...) twice or use
multi_search.with_search_queries([...]) so the federation actually merges
multiple queries), execute federated_multi_search.execute::<Document>(), and
then assert that the merged response.hits contain unique values for the "kind"
field (e.g., assert the number of hits equals the number of distinct kinds and
that no duplicate kind values appear) to prove global distinct behavior when
using FederationOptions { distinct: Some("kind".to_string()), ... }.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@src/search.rs`:
- Around line 2406-2424: The test function
test_federated_multi_search_with_distinct currently only adds one SearchQuery,
so it doesn't validate global deduplication across merged federated results;
update the test to add two different SearchQuery instances to the multi_search
(e.g., call multi_search.with_search_query(...) twice or use
multi_search.with_search_queries([...]) so the federation actually merges
multiple queries), execute federated_multi_search.execute::<Document>(), and
then assert that the merged response.hits contain unique values for the "kind"
field (e.g., assert the number of hits equals the number of distinct kinds and
that no duplicate kind values appear) to prove global distinct behavior when
using FederationOptions { distinct: Some("kind".to_string()), ... }.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: d16a40d8-eff4-4b5d-abb1-130cabb77bfd

📥 Commits

Reviewing files that changed from the base of the PR and between 82fe194 and b53fe61.

📒 Files selected for processing (1)

• src/search.rs