Horton

Re: Use WALReadFromBuffers in more places

Jingtang Zhang <mrdrivingduck@gmail.com>

View thread
From: Jingtang Zhang <mrdrivingduck@gmail.com>
To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, pgsql-hackers@lists.postgresql.org
Cc: Nitin Jadhav <nitinjadhavpostgres@gmail.com>
Date: 2024-10-15T08:22:32Z
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 →

  1. Read WAL directly from WAL buffers.

Hi all.

I've been back to this patch for a while recently. I witness that if a WAL
writer works fast, the already flushed WAL buffers will be zeroed out and
re-initialized for future use by AdvanceXLInsertBuffer in
XLogBackgroundFlush, so that WALReadFromBuffers will miss even though the
space of WAL buffer is enough. It is much more unfriendly for logical
walsenders than physical walsenders, because logical ones consume WAL
slower than physical ones due to the extra decoding phase. Seems that the
aim
of AdvanceXLInsertBuffer in WAL writer contradicts with our reading from
WAL buffer. Any thoughts?