... btw, having now looked more closely at get_xid_status(), I wonder how come there aren't more compilers bitching about it, because it is very very obviously broken. In particular, the case of requesting status for an xid that is BootstrapTransactionId or FrozenTransactionId *will* fall through to perform FullTransactionIdPrecedesOrEquals with an uninitialized fxid.
The fact that most compilers seem to fail to notice that is quite scary. I suppose it has something to do with FullTransactionId being a struct, which makes me wonder if that choice was quite as wise as we thought. Meanwhile, so far as this code goes, I wonder why you don't just change it to always set that value, ie XidBoundsViolation result; FullTransactionId fxid; FullTransactionId clog_horizon; + fxid = FullTransactionIdFromXidAndCtx(xid, ctx); + /* Quick check for special xids */ if (!TransactionIdIsValid(xid)) result = XID_INVALID; else if (xid == BootstrapTransactionId || xid == FrozenTransactionId) result = XID_BOUNDS_OK; else { /* Check if the xid is within bounds */ - fxid = FullTransactionIdFromXidAndCtx(xid, ctx); if (!fxid_in_cached_range(fxid, ctx)) { regards, tom lane