fix: search index restore when index names start with ‘:’ (e.g. :Order:index) (#5755)

* fix: load save search index fix

* fix: review comments

Author: vyavdoshenko

src/server/rdb_load.cc

@@ -2812,6 +2812,8 @@ void RdbLoader::LoadSearchIndexDefFromAux(string&& def) {
   facade::RespVec resp_vec;
   facade::RedisParser parser;
 
+  // Prepend a whitespace so names starting with ':' are treated as names, not RESP tokens.
+  def.insert(def.begin(), ' ');
   def += "\r\n";  // RESP terminator
   io::MutableBytes buffer{reinterpret_cast<uint8_t*>(def.data()), def.size()};
   auto res = parser.Parse(buffer, &consumed, &resp_vec);

src/server/rdb_test.cc

@@ -670,6 +670,26 @@ TEST_F(RdbTest, SBF) {
   EXPECT_THAT(Run({"BF.EXISTS", "k", "1"}), IntArg(1));
 }
 
+TEST_F(RdbTest, RestoreSearchIndexNameStartingWithColon) {
+  // Create an index with a name that starts with ':' and add a sample document
+  EXPECT_EQ(Run({"FT.CREATE", ":Order:index", "ON", "HASH", "PREFIX", "1", ":Order:", "SCHEMA",
+                 "customer_name", "AS", "customer_name", "TEXT", "status", "AS", "status", "TAG"}),
+            "OK");
+
+  EXPECT_THAT(Run({"HSET", ":Order:1", "customer_name", "John", "status", "new"}), IntArg(2));
+
+  // Save and reload to ensure the index definition is persisted and restored
+  EXPECT_EQ(Run({"save", "df"}), "OK");
+  EXPECT_EQ(Run({"debug", "reload"}), "OK");
+
+  // Verify a basic search works on the restored index
+  auto search = Run({"FT.SEARCH", ":Order:index", "John"});
+  ASSERT_THAT(search, ArgType(RespExpr::ARRAY));
+  const auto& v = search.GetVec();
+  ASSERT_FALSE(v.empty());
+  EXPECT_THAT(v.front(), IntArg(1));
+}
+
 TEST_F(RdbTest, DflyLoadAppend) {
   // Create an RDB with (k1,1) value in it saved as `filename`
   EXPECT_EQ(Run({"set", "k1", "1"}), "OK");