Re: [BUGS] BUG #14825: enum type: unsafe use?

Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com> writes:
> OK, I think I'm convinced. Here's is the WIP code I put together for the
> blacklist. I'm was looking for a place to put the init call, but since
> it's possibly not going anywhere I stopped :-) . My initial thought
> about substransactions was that we should ignore them for this purpose
> (That's why I used TopTransactionContext for the table).

For the blacklist, I agree we could just ignore subtransactions: all
subtransaction levels are equally uncommitted for this purpose, and
leaving entries from failed subtransactions in place seems like a
non-issue, since they'd never be referenced again. (Well, barring OID
wraparound and an enum-value-OID collision while the transaction runs,
but I think we can ignore that as having probability epsilon.)

But you need to actually put the table in TopTransactionContext, not
CurTransactionContext ;-). Also, I don't think you need an init call
so much as an end-of-transaction cleanup call. Maybe call it
AtEOXactEnum(), for consistency with other functions called in the
same area.

> w.r.t. table size - how large? I confess I haven't seen any systems with
> more than a few hundred enum types. But even a million or two shouldn't
> consume a huge amount of memory, should it?

Dynahash tables are self-expanding, so I don't see a need to stress about
that too much. Anything in 10-100 seems reasonable for initial size.

regards, tom lane