feat: add metadata field with queryUid to search responses

- Add SearchMetadata struct with queryUid field (UUID v7)
- Add metadata field to SearchResult for /search route
- Add metadata field to FederatedSearchResult for /multi-search route
- Update perform_search to generate queryUid and set metadata
- Update federated search to generate queryUid for each query
- Update multi-search non-federated path to include metadata
- Fix pattern matching in analytics and other code

The metadata field contains:
- For /search: single object with queryUid
- For /multi-search: array of objects, one per query
- For federated search: array of objects, one per query

All queryUid values are generated using Uuid::now_v7() for time-ordered uniqueness.

crates/meilisearch/src/routes/indexes/search_analytics.rs

@@ -235,6 +235,7 @@ impl<Method: AggregateMethod> SearchAggregator<Method> {
             degraded,
             used_negative_operator,
             request_uid: _,
+            metadata: _,
         } = result;
 
         self.total_succeeded = self.total_succeeded.saturating_add(1);

crates/meilisearch/src/search/federated/perform.rs

@@ -20,6 +20,7 @@ use tokio::task::JoinHandle;
 use uuid::Uuid;
 
 use super::super::ranking_rules::{self, RankingRules};
+use super::super::SearchMetadata;
 use super::super::{
     compute_facet_distribution_stats, prepare_search, AttributesFormat, ComputedFacets, HitMaker,
     HitsInfo, RetrieveVectors, SearchHit, SearchKind, SearchQuery, SearchQueryWithIndex,
@@ -59,7 +60,10 @@ pub async fn perform_federated_search(
 
     // 1. partition queries by host and index
     let mut partitioned_queries = PartitionedQueries::new();
+    let mut query_metadata = Vec::new();
     for (query_index, federated_query) in queries.into_iter().enumerate() {
+        let query_uid = Uuid::now_v7();
+        query_metadata.push(SearchMetadata { query_uid });
         partitioned_queries.partition(federated_query, query_index, &network, features)?
     }
 
@@ -173,6 +177,7 @@ pub async fn perform_federated_search(
         facets_by_index,
         remote_errors: partitioned_queries.has_remote.then_some(remote_errors),
         request_uid: Some(request_uid),
+        metadata: Some(query_metadata),
     })
 }
 
@@ -442,6 +447,7 @@ fn merge_metadata(
         degraded: degraded_for_host,
         used_negative_operator: host_used_negative_operator,
         remote_errors: _,
+        metadata: _,
         request_uid: _,
     } in remote_results
     {

crates/meilisearch/src/search/federated/types.rs

@@ -18,6 +18,8 @@ use serde::{Deserialize, Serialize};
 use utoipa::ToSchema;
 use uuid::Uuid;
 
+use crate::search::SearchMetadata;
+
 use super::super::{ComputedFacets, FacetStats, HitsInfo, SearchHit, SearchQueryWithIndex};
 use crate::milli::vector::Embedding;
 
@@ -134,6 +136,8 @@ pub struct FederatedSearchResult {
     pub facets_by_index: FederatedFacets,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub request_uid: Option<Uuid>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub metadata: Option<Vec<SearchMetadata>>,
 
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub remote_errors: Option<BTreeMap<String, ResponseError>>,
@@ -160,6 +164,7 @@ impl fmt::Debug for FederatedSearchResult {
             facets_by_index,
             remote_errors,
             request_uid,
+            metadata,
         } = self;
 
         let mut debug = f.debug_struct("SearchResult");
@@ -195,6 +200,9 @@ impl fmt::Debug for FederatedSearchResult {
         if let Some(request_uid) = request_uid {
             debug.field("request_uid", &request_uid);
         }
+        if let Some(metadata) = metadata {
+            debug.field("metadata", &metadata);
+        }
 
         debug.finish()
     }

crates/meilisearch/src/search/mod.rs

@@ -836,6 +836,13 @@ pub struct SearchHit {
     pub ranking_score_details: Option<serde_json::Map<String, serde_json::Value>>,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, ToSchema)]
+#[serde(rename_all = "camelCase")]
+#[schema(rename_all = "camelCase")]
+pub struct SearchMetadata {
+    pub query_uid: Uuid,
+}
+
 #[derive(Serialize, Clone, PartialEq, ToSchema)]
 #[serde(rename_all = "camelCase")]
 #[schema(rename_all = "camelCase")]
@@ -854,6 +861,8 @@ pub struct SearchResult {
     pub facet_stats: Option<BTreeMap<String, FacetStats>>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub request_uid: Option<Uuid>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub metadata: Option<SearchMetadata>,
 
     #[serde(skip_serializing_if = "Option::is_none")]
     pub semantic_hit_count: Option<u32>,
@@ -876,6 +885,7 @@ impl fmt::Debug for SearchResult {
             facet_distribution,
             facet_stats,
             request_uid,
+            metadata,
             semantic_hit_count,
             degraded,
             used_negative_operator,
@@ -908,6 +918,9 @@ impl fmt::Debug for SearchResult {
         if let Some(request_uid) = request_uid {
             debug.field("request_uid", &request_uid);
         }
+        if let Some(metadata) = metadata {
+            debug.field("metadata", &metadata);
+        }
 
         debug.finish()
     }
@@ -1234,6 +1247,7 @@ pub fn perform_search(
         .map(|ComputedFacets { distribution, stats }| (distribution, stats))
         .unzip();
 
+    let query_uid = Uuid::now_v7();
     let result = SearchResult {
         hits: documents,
         hits_info,
@@ -1246,6 +1260,7 @@ pub fn perform_search(
         used_negative_operator,
         semantic_hit_count,
         request_uid: Some(request_uid),
+        metadata: Some(SearchMetadata { query_uid }),
     };
     Ok(result)
 }