| From: | Mihail Nikalayeu <mihailnikalayeu(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, Melanie Plageman <melanieplageman(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Noah Misch <noah(at)leadboat(dot)com> |
| Subject: | Re: Buffer locking is special (hints, checksums, AIO writes) |
| Date: | 2025-08-23 10:31:53 |
| Message-ID: | CADzfLwV65qEO1z02Spse47pNP-vGLhaBZpDXfftb2w-28UMf5A@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hello, Andres!
Andres Freund <andres(at)anarazel(dot)de>:
>
> As part of that introduce a new lock level in-between share and exclusive
> locks (provisionally called share-exclusive, but I hate it). The new lock
> level allows other share lockers, but can only be held by one backend.
>
> This allows to change the rules so that:
>
> 1) Share lockers are not allowed to modify buffers anymore
> 2) Hint bits need the new lock mode (conditionally upgrading the lock in SetHintBits())
> 3) Write IO needs to the new lock level
IIUC, it may be mapped to existing locking system:
BUFFER_LOCK_SHARE ----> AccessShareLock
new lock mode ----> ExclusiveLock
BUFFER_LOCK_EXCLUSIVE ----> AccessExclusiveLock
So, it all may be named:
BUFFER_LOCK_ACCESS_SHARE
BUFFER_LOCK_EXCLUSIVE
BUFFER_LOCK_ACCESS_EXCLUSIVE
being more consistent with table-level locking system.
Greetings,
Mikhail.
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