Re: [HACKERS] Ye olde "relation doesn't quite exist" problem

Added to TODO:

* elog() flushes cache, try invalidating just entries from current xact


> Bruce Momjian <maillist@candle.pha.pa.us> writes:
> > OK, let me give two ideas here.  First, we could create a linked list of
> > all cache additions that happen inside a transaction.  If the
> > transaction aborts, we can invalidate all the cache entries in the list.
> > Second, we could just invalidate the entire cache on a transaction
> > abort.  Third, we could somehow invalidate the cache on transaction
> > abort "only" if there was some system table modification in the
> > transaction.  The third one seems a little harder.
> 
> Yes, the second one was the quick-and-dirty answer that occurred to me.
> That would favor apps that seldom incur errors (no extra overhead to
> keep track of cache changes), but would be bad news for those that
> often incur errors (unnecessary cache reloads).
> 
> Is there room in the SysCaches for the transaction ID of the last
> transaction to modify each entry?  That would provide an easy and
> inexpensive way of finding the ones to zap when the current xact is
> aborted, I would think: abort would just scan all the caches looking
> for entries with the current xact ID, and invalidate only those entries.
> The cost in the no-error case would just be storing an additional
> field whenever an entry is modified; seems cheap enough.  However,
> if there are a lot of different places in the code that can create/
> modify a cache entry, this could be a fair amount of work (and it'd
> carry the risk of missing some places...).
> 
> > Seems like this not something for 6.5.
> 
> I think we really ought to do *something*.  I'd settle for the
> brute-force blow-away-all-the-caches answer for now, though.
> 
>             regards, tom lane
> 
> 


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