How does the SQL Server Fulltext Index grow?

Question

I'm trying to get an idea of fulltext index growth and gauge its long-term memory needs.

Does it keep a cache of each search? (Knowing that the first search for a new keywords always takes slightly longer, and is subsequently faster) Will it grow indefinitely?

Or is its size pretty much finite after its creation?

Should I expect performance degradation, stagnation, or improvement over time?

Answer 1

As a general rule, a FT catalog will grow proportionally with the number of documents indexed. Caching of FT indexes falls under the general category of SQL Server buffer pool caching.

Have a look at SQL Server 2005 Full-Text Queries on Large Catalogs: Lessons Learned

Tuning full-text queries on very large catalogs requires some experimentation. We observed that full-text query performance is roughly proportional to the number of rows returned for a given set of search words. We found improvements in performance by using CONTAINSTABLE rather than the CONTAINS function, and by removing unnecessary joins.

Note though that there are significant changes in FT performance between SQL 2005 and SQL 2008.