On Thu, Sep 21, 2017 at 5:48 AM, Peter Koukoulis <pkoukou...@gmail.com> wrote:
> Hi > > I have a query where a filter would always be negative, how many steps, > out these: > > - parsing and syntax check > - semantic analysis > - transformation process (query rewrite based on system or > user-defined rules) > - query optimization > - execution > > would be performed or not? Also, where in the documentation can I found > out which of the above phases would be performed? > > For example, for a query such as the following: > > select x,y from test1 where 1=0; > > I'm inferring behavior here but... All of them. You are still going to get a result set with zero records and the correct column structure. i.e., "Execution". None of the other stuff can be skipped in getting to engine to that point. With a "always false" predicate and that simple of a query structure most of the other stuff, including execution, is probably performed is seemingly zero time but it still has to work through that step of the process - if nothing else than to move through an if-branch to decide that nothing material needs to be done. David J.
