add support for field exclusion/inclusion lists in queries
#1 Updated by Eric Faulhaber over 11 years ago
This feature supports a performance optimization in which -- for read-only usage of a table -- the query's results only return the list of IDs or a minimum set of data (i.e., minimum set of columns) rather than the entire record. The wider (more columns) a table, the more likely we are to see a performance gain from this approach.
This optimization presumes we can determine with confidence that the usage of the query is read-only; the NO-LOCK option is a good indicator, but it is not foolproof: a follow-on EXCLUSIVE-LOCK query can invalidate any performance gained with this approach.