Commit 61c2e1a9 allowed parallel
query to be used in more places, revealing via buildfarm member
mandrill that several functions intended to be called from triggers
were incorrectly marked parallel-safe rather than parallel-restricted.

Report by Tom Lane.  Patch by Rafia Sabih.  Reviewed by me.

Discussion: http://postgr.es/m/16061.1490479253@sss.pgh.pa.us