On Wed, Mar 11, 2015 at 8:00 PM, Kevin Grittner <kgrittn@ymail.com> wrote:
If there are no false positives, turning it on is zero impact (except for any performance impact involved in detecting the condition) for those who have no problems.
Think of this as a bug fix. Hopefully nobody was using the syntax before because it didn't work right and if it did they were depending on the broken behaviour. But once it's fixed it would be frustrating to have it be fixed but have a warning saying "WARNING this query works fine now but didn't work in previous versions". Especially since warnings in DML are effectively fatal errors due to the frequency that they'll fire.
The warning can be useful for people testing code written in old versions or writing code intended to be multi-version compatible. But it's not something someone would want if they're writing code for 9.5.