BTW, while I'm looking at this: it seems like the "index" arrays in
struct TrigDesc are really a lot more complication than they are worth.
It'd be far easier to dispense with them and instead iterate through
the main trigger array, skipping any triggers whose tgtype doesn't match
what we need. If you had a really huge number of triggers on a table,
it's possible that could be marginally slower, but I'm having a hard
time envisioning practical situations where anybody could tell the
difference.
regards, tom lane