fix(search): use LOWER()+LIKE instead of ILIKE for pg_bigm index compat

ILIKE bypasses pg_bigm GIN indexes. Instead, lowercase the query in Go
and use LOWER(column) LIKE in SQL. Rebuild bigram indexes on LOWER()
expressions to match.

server/internal/handler/issue.go

@@ -203,7 +203,7 @@ func (h *Handler) SearchIssues(w http.ResponseWriter, r *http.Request) {
 	includeClosed := r.URL.Query().Get("include_closed") == "true"
 
 	wsUUID := parseUUID(workspaceID)
-	queryText := strToText(escapeLike(q))
+	queryText := strToText(strings.ToLower(escapeLike(q)))
 
 	rows, err := h.Queries.SearchIssues(ctx, db.SearchIssuesParams{
 		WorkspaceID:   wsUUID,

server/migrations/036_search_case_insensitive.down.sql

@@ -0,0 +1,20 @@
+-- Revert to original (non-LOWER) bigram indexes.
+DO $$
+BEGIN
+  DROP INDEX IF EXISTS idx_issue_title_bigm;
+  DROP INDEX IF EXISTS idx_issue_description_bigm;
+  CREATE INDEX idx_issue_title_bigm ON issue USING gin (title gin_bigm_ops);
+  CREATE INDEX idx_issue_description_bigm ON issue USING gin (COALESCE(description, '') gin_bigm_ops);
+EXCEPTION WHEN OTHERS THEN
+  RAISE NOTICE 'skipping bigram index rebuild (pg_bigm not installed)';
+END
+$$;
+
+DO $$
+BEGIN
+  DROP INDEX IF EXISTS idx_comment_content_bigm;
+  CREATE INDEX idx_comment_content_bigm ON comment USING gin (content gin_bigm_ops);
+EXCEPTION WHEN OTHERS THEN
+  RAISE NOTICE 'skipping bigram index rebuild on comment (pg_bigm not installed)';
+END
+$$;

server/migrations/036_search_case_insensitive.up.sql

@@ -0,0 +1,21 @@
+-- Replace bigram indexes with LOWER() versions for case-insensitive search.
+-- Only created when pg_bigm is installed.
+DO $$
+BEGIN
+  DROP INDEX IF EXISTS idx_issue_title_bigm;
+  DROP INDEX IF EXISTS idx_issue_description_bigm;
+  CREATE INDEX idx_issue_title_bigm ON issue USING gin (LOWER(title) gin_bigm_ops);
+  CREATE INDEX idx_issue_description_bigm ON issue USING gin (LOWER(COALESCE(description, '')) gin_bigm_ops);
+EXCEPTION WHEN OTHERS THEN
+  RAISE NOTICE 'skipping bigram index rebuild (pg_bigm not installed)';
+END
+$$;
+
+DO $$
+BEGIN
+  DROP INDEX IF EXISTS idx_comment_content_bigm;
+  CREATE INDEX idx_comment_content_bigm ON comment USING gin (LOWER(content) gin_bigm_ops);
+EXCEPTION WHEN OTHERS THEN
+  RAISE NOTICE 'skipping bigram index rebuild on comment (pg_bigm not installed)';
+END
+$$;

server/pkg/db/generated/issue.sql.go

@@ -431,16 +431,16 @@ const searchIssues = `-- name: SearchIssues :many
 SELECT i.id, i.workspace_id, i.title, i.description, i.status, i.priority, i.assignee_type, i.assignee_id, i.creator_type, i.creator_id, i.parent_issue_id, i.acceptance_criteria, i.context_refs, i.position, i.due_date, i.created_at, i.updated_at, i.number, i.project_id,
   COUNT(*) OVER() AS total_count,
   CASE
-    WHEN i.title LIKE '%' || $1 || '%' THEN 'title'
-    WHEN COALESCE(i.description, '') LIKE '%' || $1 || '%' THEN 'description'
+    WHEN LOWER(i.title) LIKE '%' || $1 || '%' THEN 'title'
+    WHEN LOWER(COALESCE(i.description, '')) LIKE '%' || $1 || '%' THEN 'description'
     ELSE 'comment'
   END AS match_source,
   CASE
-    WHEN i.title LIKE '%' || $1 || '%' THEN ''
-    WHEN COALESCE(i.description, '') LIKE '%' || $1 || '%' THEN ''
+    WHEN LOWER(i.title) LIKE '%' || $1 || '%' THEN ''
+    WHEN LOWER(COALESCE(i.description, '')) LIKE '%' || $1 || '%' THEN ''
     ELSE COALESCE(
       (SELECT c.content FROM comment c
-       WHERE c.issue_id = i.id AND c.content LIKE '%' || $1 || '%'
+       WHERE c.issue_id = i.id AND LOWER(c.content) LIKE '%' || $1 || '%'
        ORDER BY c.created_at DESC LIMIT 1),
       ''
     )
@@ -448,18 +448,18 @@ SELECT i.id, i.workspace_id, i.title, i.description, i.status, i.priority, i.ass
 FROM issue i
 WHERE i.workspace_id = $2
   AND (
-    i.title LIKE '%' || $1 || '%'
-    OR COALESCE(i.description, '') LIKE '%' || $1 || '%'
+    LOWER(i.title) LIKE '%' || $1 || '%'
+    OR LOWER(COALESCE(i.description, '')) LIKE '%' || $1 || '%'
     OR EXISTS (
       SELECT 1 FROM comment c
-      WHERE c.issue_id = i.id AND c.content LIKE '%' || $1 || '%'
+      WHERE c.issue_id = i.id AND LOWER(c.content) LIKE '%' || $1 || '%'
     )
   )
   AND ($3::boolean OR i.status NOT IN ('done', 'cancelled'))
 ORDER BY
   CASE
-    WHEN i.title LIKE '%' || $1 || '%' THEN 0
-    WHEN COALESCE(i.description, '') LIKE '%' || $1 || '%' THEN 1
+    WHEN LOWER(i.title) LIKE '%' || $1 || '%' THEN 0
+    WHEN LOWER(COALESCE(i.description, '')) LIKE '%' || $1 || '%' THEN 1
     ELSE 2
   END,
   i.updated_at DESC
@@ -499,6 +499,7 @@ type SearchIssuesRow struct {
 	MatchedCommentContent interface{}        `json:"matched_comment_content"`
 }
 
+// @query is expected to be pre-lowercased by the caller.
 func (q *Queries) SearchIssues(ctx context.Context, arg SearchIssuesParams) ([]SearchIssuesRow, error) {
 	rows, err := q.db.Query(ctx, searchIssues,
 		arg.Query,

server/pkg/db/queries/issue.sql

@@ -81,19 +81,20 @@ WHERE parent_issue_id = $1
 ORDER BY position ASC, created_at DESC;
 
 -- name: SearchIssues :many
+-- @query is expected to be pre-lowercased by the caller.
 SELECT i.*,
   COUNT(*) OVER() AS total_count,
   CASE
-    WHEN i.title LIKE '%' || @query || '%' THEN 'title'
-    WHEN COALESCE(i.description, '') LIKE '%' || @query || '%' THEN 'description'
+    WHEN LOWER(i.title) LIKE '%' || @query || '%' THEN 'title'
+    WHEN LOWER(COALESCE(i.description, '')) LIKE '%' || @query || '%' THEN 'description'
     ELSE 'comment'
   END AS match_source,
   CASE
-    WHEN i.title LIKE '%' || @query || '%' THEN ''
-    WHEN COALESCE(i.description, '') LIKE '%' || @query || '%' THEN ''
+    WHEN LOWER(i.title) LIKE '%' || @query || '%' THEN ''
+    WHEN LOWER(COALESCE(i.description, '')) LIKE '%' || @query || '%' THEN ''
     ELSE COALESCE(
       (SELECT c.content FROM comment c
-       WHERE c.issue_id = i.id AND c.content LIKE '%' || @query || '%'
+       WHERE c.issue_id = i.id AND LOWER(c.content) LIKE '%' || @query || '%'
        ORDER BY c.created_at DESC LIMIT 1),
       ''
     )
@@ -101,18 +102,18 @@ SELECT i.*,
 FROM issue i
 WHERE i.workspace_id = @workspace_id
   AND (
-    i.title LIKE '%' || @query || '%'
-    OR COALESCE(i.description, '') LIKE '%' || @query || '%'
+    LOWER(i.title) LIKE '%' || @query || '%'
+    OR LOWER(COALESCE(i.description, '')) LIKE '%' || @query || '%'
     OR EXISTS (
       SELECT 1 FROM comment c
-      WHERE c.issue_id = i.id AND c.content LIKE '%' || @query || '%'
+      WHERE c.issue_id = i.id AND LOWER(c.content) LIKE '%' || @query || '%'
     )
   )
   AND (@include_closed::boolean OR i.status NOT IN ('done', 'cancelled'))
 ORDER BY
   CASE
-    WHEN i.title LIKE '%' || @query || '%' THEN 0
-    WHEN COALESCE(i.description, '') LIKE '%' || @query || '%' THEN 1
+    WHEN LOWER(i.title) LIKE '%' || @query || '%' THEN 0
+    WHEN LOWER(COALESCE(i.description, '')) LIKE '%' || @query || '%' THEN 1
     ELSE 2
   END,
   i.updated_at DESC