Re: Why to index a "Recently DEAD" tuple when creating index

Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com> writes:
>> 2. If we only support "Read Committed" isolation level, is there a safe way to not index such data?

> I can't think of a case where the RECENTLY_DELETED tuple needs to be
> indexed in "Read Committed" case.

I think you're making dangerously optimistic assumptions about how
long a query snapshot might survive in READ COMMITTED mode.

In particular, I suspect you're reasoning that the new index couldn't
be used except by a freshly-created query plan, which is possibly
true, and that such a plan must be used with a freshly-created
snapshot, which is simply wrong. A counterexample could be built
using a SQL or PL function that's marked STABLE, because such a
function is defined to be executed using the calling query's
snapshot. But it'll make query plans using current reality.

regards, tom lane