Re: [HACKERS] GSoC 2017: Foreign Key Arrays

Indeed, this is right.

But look how that works for regular FK.  When you declare a FK, you necessary need unique index on referenced column(s).  However, index on referencing columns(s) is not required.  Without index on referencing column(s), row delete in referenced table and update of referenced column are expensive because requires sequential scan of referencing table.  Users are encouraged to index referencing column(s) to accelerate queries produced by RI triggers. [1]