I have seen two different designs for incremental index updates. 1) Have two copies of indexes A and B. The incremental updates happens on A index while B index is being used for search. Then, hot swap the two indexes. Bring B index up to date and perform incremental updates thereafter. In this scenario, searches are performed on index A or B alternatively.
2) Have a master index where the incremental updates are applied. Then, the slave indexes got synced up with the master index. Searches are performed only on the slave indexes. So, I want to know what are the trade offs between the two approaches? For scalability, what's the best approach? Thanks, Jian