Re: Change the bool member of the Query structure to bits

From: Quan Zongliang <quanzongliang(at)yeah(dot)net>
To: Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Change the bool member of the Query structure to bits
Date: 2024-02-20 23:46:53
Message-ID: 954eace7-8fca-4a0e-b05c-2f907e2d081a@yeah.net
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On 2024/2/20 19:18, Tomas Vondra wrote:
> On 2/20/24 11:11, Quan Zongliang wrote:
>>
>> Sorry. I forgot to save a file. This is the latest.
>>
>> On 2024/2/20 18:07, Quan Zongliang wrote:
>>>
>>> The Query structure has an increasing number of bool attributes. This
>>> is likely to increase in the future. And they have the same
>>> properties. Wouldn't it be better to store them in bits? Common
>>> statements don't use them, so they have little impact. This also saves
>>> memory space.
>>>
>
> Hi,
>
> Are we really adding bools to Query that often? A bit of git-blame says
> it's usually multiple years to add a single new flag, which is what I'd
> expect. I doubt that'll change.
>
> As for the memory savings, can you quantify how much memory this would save?
>
> I highly doubt that's actually true (or at least measurable). The Query
> struct has ~256B, the patch cuts that to ~232B. But we allocate stuff in
> power-of-2, so we'll allocate 256B chunk anyway. And we allocate very
> few of those objects anyway ...
>
> regards
>
That makes sense. Withdraw.

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