add safeRead

server/db/pg/index.ts

@@ -1,4 +1,5 @@
 export * from "./driver";
+export * from "./safeRead";
 export * from "./schema/schema";
 export * from "./schema/privateSchema";
 export * from "./migrate";

server/db/pg/safeRead.ts

@@ -0,0 +1,24 @@
+import { db, primaryDb } from "./driver";
+
+/**
+ * Runs a read query with replica fallback for Postgres.
+ * Executes the query against the replica first (when replicas exist).
+ * If the query throws or returns no data (null, undefined, or empty array),
+ * runs the same query against the primary.
+ */
+export async function safeRead<T>(
+    query: (d: typeof db | typeof primaryDb) => Promise<T>
+): Promise<T> {
+    try {
+        const result = await query(db);
+        if (result === undefined || result === null) {
+            return query(primaryDb);
+        }
+        if (Array.isArray(result) && result.length === 0) {
+            return query(primaryDb);
+        }
+        return result;
+    } catch {
+        return query(primaryDb);
+    }
+}

server/db/sqlite/index.ts

@@ -1,4 +1,5 @@
 export * from "./driver";
+export * from "./safeRead";
 export * from "./schema/schema";
 export * from "./schema/privateSchema";
 export * from "./migrate";

server/db/sqlite/safeRead.ts

@@ -0,0 +1,11 @@
+import { db } from "./driver";
+
+/**
+ * Runs a read query. For SQLite there is no replica/primary distinction,
+ * so the query is executed once against the database.
+ */
+export async function safeRead<T>(
+    query: (d: typeof db) => Promise<T>
+): Promise<T> {
+    return query(db);
+}