Introduce a lot of search parameters and make Deserr happy

crates/milli/src/index.rs

@@ -1695,7 +1695,7 @@ impl Index {
 
     pub fn chat_config(&self, txn: &RoTxn<'_>) -> heed::Result<ChatConfig> {
         self.main
-            .remap_types::<Str, SerdeBincode<_>>()
+            .remap_types::<Str, SerdeJson<_>>()
             .get(txn, main_key::CHAT)
             .map(|o| o.unwrap_or_default())
     }
@@ -1705,7 +1705,7 @@ impl Index {
         txn: &mut RwTxn<'_>,
         val: &ChatConfig,
     ) -> heed::Result<()> {
-        self.main.remap_types::<Str, SerdeBincode<_>>().put(txn, main_key::CHAT, &val)
+        self.main.remap_types::<Str, SerdeJson<_>>().put(txn, main_key::CHAT, &val)
     }
 
     pub(crate) fn delete_chat_config(&self, txn: &mut RwTxn<'_>) -> heed::Result<bool> {
@@ -1943,15 +1943,54 @@ pub struct ChatConfig {
     pub description: String,
     /// Contains the document template and max template length.
     pub prompt: PromptData,
+    pub search_parameters: SearchParameters,
+}
+
+#[derive(Debug, Default, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SearchParameters {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub hybrid: Option<HybridQuery>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub limit: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub sort: Option<Vec<String>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub distinct: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub matching_strategy: Option<MatchingStrategy>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub attributes_to_search_on: Option<Vec<String>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub ranking_score_threshold: Option<f64>,
+}
+
+#[derive(Debug, Default, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct HybridQuery {
+    pub semantic_ratio: f32,
+    pub embedder: String,
 }
 
 #[derive(Debug, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
 pub struct PrefixSettings {
     pub prefix_count_threshold: usize,
     pub max_prefix_length: usize,
     pub compute_prefixes: PrefixSearch,
 }
 
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub enum MatchingStrategy {
+    /// Remove query words from last to first
+    Last,
+    /// All query words are mandatory
+    All,
+    /// Remove query words from the most frequent to the least
+    Frequency,
+}
+
 #[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Default)]
 #[serde(rename_all = "camelCase")]
 pub enum PrefixSearch {