Re: Improve WALRead() to suck data directly from WAL buffers when possible

Jeff Davis <pgsql@j-davis.com>

From: Jeff Davis <pgsql@j-davis.com>

To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Andres Freund <andres@anarazel.de>

Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Dilip Kumar <dilipbalaut@gmail.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, pgsql-hackers@lists.postgresql.org, Nathan Bossart <nathandbossart@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>

Date: 2024-02-14T01:32:30Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Add XLogCtl->logInsertResult
- f3ff7bf83bce 17.0 cited
Add assert to WALReadFromBuffers().
- 9ecbf54075a9 17.0 landed
Read WAL directly from WAL buffers.
- 91f2cae7a4e6 17.0 landed
Additional write barrier in AdvanceXLInsertBuffer().
- 766571be1659 17.0 landed
Use 64-bit atomics for xlblocks array elements.
- c3a8e2a7cb16 17.0 landed
Don't trust unvalidated xl_tot_len.
- bae868caf222 17.0 cited

On Tue, 2024-02-13 at 22:47 +0530, Bharath Rupireddy wrote:
> c) If planning to replicate unflushed data, then ensure all the
> WALRead() callers wait until startptr+count is past the current
> insert
> position with WaitXLogInsertionsToFinish().

WALRead() can't read past the Write pointer, so there's no point in
calling WaitXLogInsertionsToFinish(), right?


Regards,
	Jeff Davis