feat(analytics): add personalization tracking to segment analytics

- Add total_personalized field to SearchAggregator to track personalization usage
- Track when search requests include personalization parameters
- Include personalization data in analytics JSON output
- Maintain clean personalization service interface

crates/meilisearch/src/personalization/mod.rs

@@ -23,15 +23,14 @@ impl CohereService {
         query: Option<&str>,
     ) -> Result<SearchResult, ResponseError> {
         // Extract user context from personalization
-        let Some(personalize) = personalize else { return Ok(search_result) };
-        let user_context = personalize.user_context.as_deref();
+        let Some(user_context) = personalize.and_then(|p| p.user_context.as_deref()) else {
+            return Ok(search_result);
+        };
 
         // Build the prompt by merging query and user context
-        let prompt = match (query, user_context) {
-            (Some(q), Some(uc)) => format!("User Context: {}\nQuery: {}", uc, q),
-            (Some(q), None) => q.to_string(),
-            (None, Some(uc)) => format!("User Context: {}", uc),
-            (None, None) => return Ok(search_result),
+        let prompt = match query {
+            Some(q) => format!("User Context: {user_context}\nQuery: {q}"),
+            None => format!("User Context: {user_context}"),
         };
 
         // Extract documents for reranking
@@ -65,7 +64,6 @@ impl CohereService {
                 // Create a mapping from original index to new rank
                 let reranked_indices: Vec<usize> =
                     rerank_response.iter().map(|result| result.index as usize).collect();
-                debug!("Reranked indices: {:?}", reranked_indices);
 
                 // Reorder the hits based on Cohere's reranking
                 let mut reranked_hits = Vec::new();

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

@@ -94,6 +94,9 @@ pub struct SearchAggregator<Method: AggregateMethod> {
     show_ranking_score_details: bool,
     ranking_score_threshold: bool,
 
+    // personalization
+    total_personalized: usize,
+
     marker: std::marker::PhantomData<Method>,
 }
 
@@ -128,7 +131,7 @@ impl<Method: AggregateMethod> SearchAggregator<Method> {
             hybrid,
             ranking_score_threshold,
             locales,
-            personalize: _,
+            personalize,
         } = query;
 
         let mut ret = Self::default();
@@ -203,6 +206,11 @@ impl<Method: AggregateMethod> SearchAggregator<Method> {
             ret.locales = locales.iter().copied().collect();
         }
 
+        // personalization
+        if personalize.is_some() {
+            ret.total_personalized = 1;
+        }
+
         ret.highlight_pre_tag = *highlight_pre_tag != DEFAULT_HIGHLIGHT_PRE_TAG();
         ret.highlight_post_tag = *highlight_post_tag != DEFAULT_HIGHLIGHT_POST_TAG();
         ret.crop_marker = *crop_marker != DEFAULT_CROP_MARKER();
@@ -291,6 +299,7 @@ impl<Method: AggregateMethod> Aggregate for SearchAggregator<Method> {
             total_used_negative_operator,
             ranking_score_threshold,
             mut locales,
+            total_personalized,
             marker: _,
         } = *new;
 
@@ -375,6 +384,9 @@ impl<Method: AggregateMethod> Aggregate for SearchAggregator<Method> {
         // locales
         self.locales.append(&mut locales);
 
+        // personalization
+        self.total_personalized = self.total_personalized.saturating_add(total_personalized);
+
         self
     }
 
@@ -419,6 +431,7 @@ impl<Method: AggregateMethod> Aggregate for SearchAggregator<Method> {
             total_used_negative_operator,
             ranking_score_threshold,
             locales,
+            total_personalized,
             marker: _,
         } = *self;
 
@@ -491,6 +504,9 @@ impl<Method: AggregateMethod> Aggregate for SearchAggregator<Method> {
                 "show_ranking_score_details": show_ranking_score_details,
                 "ranking_score_threshold": ranking_score_threshold,
             },
+            "personalization": {
+                "total_personalized": total_personalized,
+            },
         })
     }
 }