One of the queries in ri_triggers.c has be a little baffled. For (relatively) obvious reasons, a FK insert triggers a SELECT 1 FROM pk_rel ... FOR KEY SHARE. For not-so-obvious reasons, a PK delete triggers a SELECT 1 FROM fk_rel ... FOR KEY SHARE.
I can't see what the lock on fk_rel achieves. Both operations are already contending for the lock on the PK row, which seems like enough to cover every eventuality. And even if the lock serves a purpose, KEY SHARE is an odd choice, since the referencing field is, in general, not a "key" in this sense. Can anyone provide an explanation / counterexample?
