From 9aa16b072951d2563c5f0a990dab571551fe6e64 Mon Sep 17 00:00:00 2001
From: Nils Schneider <nils.schneider@posteo.de>
Date: Sun, 30 Nov 2025 23:50:38 +0100
Subject: [PATCH] feat: implement hybrid document search combining Quickwit
 results with PostgreSQL `pg_trgm` title search, supported by a new index.

---
 .../down.sql                                  |  1 +
 .../202511300100_add_title_trgm_index/up.sql  |  6 ++++
 backend/src/services/documents.rs             | 32 +++++++++++++++----
 3 files changed, 33 insertions(+), 6 deletions(-)
 create mode 100644 backend/migrations/202511300100_add_title_trgm_index/down.sql
 create mode 100644 backend/migrations/202511300100_add_title_trgm_index/up.sql

diff --git a/backend/migrations/202511300100_add_title_trgm_index/down.sql b/backend/migrations/202511300100_add_title_trgm_index/down.sql
new file mode 100644
index 0000000..ab856cb
--- /dev/null
+++ b/backend/migrations/202511300100_add_title_trgm_index/down.sql
@@ -0,0 +1 @@
+DROP INDEX IF EXISTS tenant.idx_documents_title_trgm;
diff --git a/backend/migrations/202511300100_add_title_trgm_index/up.sql b/backend/migrations/202511300100_add_title_trgm_index/up.sql
new file mode 100644
index 0000000..ff1f0a6
--- /dev/null
+++ b/backend/migrations/202511300100_add_title_trgm_index/up.sql
@@ -0,0 +1,6 @@
+CREATE EXTENSION IF NOT EXISTS pg_trgm;
+
+CREATE INDEX idx_documents_title_trgm
+    ON tenant.documents
+    USING gin (title gin_trgm_ops)
+    WHERE deleted_at IS NULL;
diff --git a/backend/src/services/documents.rs b/backend/src/services/documents.rs
index 646beb6..dcee033 100644
--- a/backend/src/services/documents.rs
+++ b/backend/src/services/documents.rs
@@ -476,7 +476,9 @@ impl<'a> DocumentsService<'a> {
         let mut quickwit_order: Option<Vec<Uuid>> = None;
 
         if let Some(query_str) = search_text.as_ref() {
-            debug!(query = %query_str, "performing quickwit document search");
+            debug!(query = %query_str, "performing hybrid document search");
+            
+            // 1. Quickwit Search
             let endpoint = self
                 .state
                 .config
@@ -489,19 +491,37 @@ impl<'a> DocumentsService<'a> {
                 .as_ref()
                 .ok_or_else(|| AppError::internal("quickwit index not configured for tenant"))?;
 
-            let ids = quickwit_search(endpoint, index, tenant_id, query_str)
+            let quickwit_ids = quickwit_search(endpoint, index, tenant_id, query_str)
                 .await
                 .map_err(|err| {
                     error!(error = ?err, "quickwit search failed");
                     AppError::internal("quickwit search failed")
                 })?;
 
-            if ids.is_empty() {
+            // 2. Postgres Title Search
+            let postgres_ids: Vec<Uuid> = documents::table
+                .filter(documents::tenant_id.eq(tenant_id))
+                .filter(documents::deleted_at.is_null())
+                .filter(documents::title.ilike(format!("%{}%", query_str)))
+                .select(documents::id)
+                .load(conn)?;
+
+            // 3. Combine Results
+            let mut combined_ids = quickwit_ids.clone();
+            let quickwit_set: HashSet<Uuid> = quickwit_ids.iter().cloned().collect();
+            
+            for id in postgres_ids {
+                if !quickwit_set.contains(&id) {
+                    combined_ids.push(id);
+                }
+            }
+
+            if combined_ids.is_empty() {
                 return Ok(Vec::new());
             }
 
-            quickwit_order = Some(ids.clone());
-            let set: HashSet<Uuid> = ids.into_iter().collect();
+            quickwit_order = Some(combined_ids.clone());
+            let set: HashSet<Uuid> = combined_ids.into_iter().collect();
             filter_ids = intersect_option_sets(filter_ids, set);
         }
 
@@ -593,7 +613,7 @@ impl<'a> DocumentsService<'a> {
         let mut responses = self.hydrate_documents(conn, tenant_id, user_id, docs)?;
 
         if let Some(order) = quickwit_order {
-            let order_map: HashMap<Uuid, usize> = order
+             let order_map: HashMap<Uuid, usize> = order
                 .into_iter()
                 .enumerate()
                 .map(|(idx, id)| (id, idx))