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From: Ranier Vilela <[email protected]>
To: Richard Guo <[email protected]>
Cc: Pg Hackers <[email protected]>
Subject: Re: Avoid unncessary always true test (src/backend/storage/buffer/bufmgr.c)
Date: Mon, 5 Jun 2023 08:24:13 -0300
Message-ID: <CAEudQArzX-q7FuvHxcEQKP9RuM7eFw4CnvU_xQtkiu4+tnaA4A@mail.gmail.com> (raw)
In-Reply-To: <CAEudQArD04043ahRO_9mXiYSfhvsac4SSyskUVk5PTm73Ab24A@mail.gmail.com>
References: <CAEudQAoSA7saBF7RaoYbRjE+Zojojin0Qc9A4hebPKB8o1J+EQ@mail.gmail.com>
	<CAMbWs4_Jv4p_ib2ZZvUYhgoeSpOABjAW_4chkAhrSU=iW8CRGA@mail.gmail.com>
	<CAEudQArD04043ahRO_9mXiYSfhvsac4SSyskUVk5PTm73Ab24A@mail.gmail.com>

Em seg., 5 de jun. de 2023 às 08:06, Ranier Vilela <[email protected]>
escreveu:

> Em dom., 4 de jun. de 2023 às 23:37, Richard Guo <[email protected]>
> escreveu:
>
>>
>> On Sun, Jun 4, 2023 at 8:42 PM Ranier Vilela <[email protected]> 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;
> }
>
Sorry Richard, nevermind.

My fault, I withdraw this patch.

regards,
Ranier Vilela

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