Re: Avoid unncessary always true test (src/backend/storage/buffer/bufmgr.c)

Em dom., 4 de jun. de 2023 às 23:37, Richard Guo <guofenglinux(at)gmail(dot)com>
escreveu:

>
> On Sun, Jun 4, 2023 at 8:42 PM Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> wrote:
>
>> Hi,
>>
>> Per Coverity.
>>
>> At function ExtendBufferedRelShared, has a always true test.
>> eb.rel was dereferenced one line above, so in
>> if (eb.rel) is always true.
>>
>> I think it's worth removing the test, because Coverity raises dozens of
>> alerts thinking eb.rel might be NULL.
>> Besides, one less test is one less branch.
>>
>
> This also happens in ExtendBufferedRelTo, and the comment there explains
> that the eb.rel 'could have been closed while waiting for lock'.
>
Well, RelationGetSmgr also dereferences eb.rel.
If eb.rel could be closed while waiting for lock,
anyone who references eb.rel below takes a risk?

static inline SMgrRelation
RelationGetSmgr(Relation rel)
{
if (unlikely(rel->rd_smgr == NULL))
smgrsetowner(&(rel->rd_smgr), smgropen(rel->rd_locator, rel->rd_backend));
return rel->rd_smgr;
}

regards,
Ranier Vilela