I have implemented sphinx to search the words and it's working fine. Currently i am creating indexes of all records present in table using
$ sudo /usr/local/bin/searchd --config /usr/local/etc/sphinx.conf
But, now i want to create partial indexes i.e indexing should happen only for newly added records in table and old indexes should also persist.
It is not possible to add new entries into plain indexes in Sphinx. You can only update attributes on them or use so-called delta indexing scheme.
Another approach is using real-time indexes which can be updated using SphinxQL queries.