1. A network switch to support scalable and flexible table search, comprising: a packet processing pipeline including a plurality of packet processing clusters configured to process a received packet through multiple packet processing stages based on table search/lookup results; a plurality of search logic units each corresponding one of the plurality of packet processing clusters, wherein each of the search logic units is configured to: convert a unified table search request from its corresponding packet processing cluster to a plurality table search commands specific to one or more memory clusters that maintain a plurality of tables; provide the plurality table search commands specific to the memory clusters in parallel; collect and provide the table search results from the memory clusters to the corresponding packet processing cluster; said one or more memory clusters configured to: maintain the tables to be searched; search the tables in parallel according to the plurality table search commands from the search logic unit; process and provide the table search results to the search logic unit.