In 8.3.0, I'm seeing some oddities with SQL functions which I thought were immune to the planner data restrictions of plpgsql functions and the sort. Basically I have a query which executes in 5ms but when wrapped in a SQL function, takes 500ms. I've checked all the types passed in to make sure they match so there is no type conversions taking place in execution.
I'm curious about the validity of my expectation that functions created with SQL as the language should be as fast as the straight SQL counterpart. I've previously not run into such an order of magnitude difference in using SQL functions. Is this a change of behavior in 8.3 from 8.2? Without specific examples, are there any recommendations on how to speed up these functions?