* optimize merge strategy
Signed-off-by: Nyhmo <yihua.mo@zilliz.com>

* #2365
Signed-off-by: Ngroot <yihua.mo@zilliz.com>

* fix typo
Signed-off-by: Ngroot <yihua.mo@zilliz.com>

* optimize search
Signed-off-by: Ngroot <yihua.mo@zilliz.com>

* code format
Signed-off-by: Ngroot <yihua.mo@zilliz.com>