For those of you who have worked with previous version of Documentum Content Server (5.2.x and below) and are using 5.3.x, you should already know that with the release of 5.3, Documentum has switched their full text engine from Verity to FAST. Given that FAST engine is entirely different from Verity engine, Documentum has tried to document some of the inner workings for FAST. Most of the information I am describing can be found in Ed Bueché‘s Tuning Webtop: Advanced Search FTDQL Behavior.
Fascinating Fact #1:
Since FAST is no longer directly tied to the installation of Content Server, you have the option of not installing FAST. If you do not install the full text search engine, simple search will perform a database search (case sensitive) against object_name, title, and subject attribute against all dm_sysobjects.
Fascinating Fact #2:
One of the key features with FAST engine is that by default, all attribute values are indexed along with the content. In Verity, we had to explicitly define which attributes to include as part of the index. The reasoning behind this is that Documentum determined that in most cases the full text engine would perform significantly better searching on attribute information than using database engine. This performance improvement is evident in the following two scenarios:
- Searching for both attribute value(s) along with full text search
- Case insensitive search for attribute value(s)
Fascinating Fact #3:
The price of the performance improvement comes at a cost. In the following scenarios, the actual search performance declines:
- ID based searches
- Date ranges
- Queries using the FOLDER(DESCEND) predicate.
If your users are mainly performing attribute value searches using some ID value (eg invoice number) and are not concerned with full text search, then the default configuration for advanced search to use full text search should be changed.