Re: patch: prevent user from setting wal_buffers over 2GB bytes

Takashi Horikawa <t-horikawa(at)aj(dot)jp(dot)nec(dot)com> writes:
>>>> Why does this cause a core dump? We could consider fixing whatever
>>>> the problem is rather than capping the value.

> As far as I experiment with my own evaluation environment using
> PostgreSQL-9.4.4 on a x86_64 Linux, this problem can be fixed with the patch
> attached.

I'm unsure whether this represents a complete fix ... but even if it does,
it would be awfully easy to re-introduce similar bugs in future code
changes, and who would notice? Josh's approach of restricting the buffer
size seems a lot more robust.

If there were any practical use-case for such large WAL buffers then it
might be worth spending some effort/risk here. But AFAICS, there is not.
Indeed, capping wal_buffers might be argued to be a good thing in itself
because it would prevent users from wasting shared memory foolishly.

So my vote is for the original approach. (I've not read Josh's patch,
so there might be something wrong with it in detail, but I like the
basic approach.)

regards, tom lane