Thread

1. Review observations for partial REFRESH MATERIALIZED VIEW patc

   vellaipandiyan sm <vellaipandiyan.sm@gmail.com> — 2026-05-19T05:42:51Z

   Hello hackers,
   
   I reviewed the REFRESH MATERIALIZED VIEW ... WHERE patch and had a few
   questions around concurrency semantics.
   
      - The original DELETE -> INSERT approach exposing a consistency gap
      makes sense, especially once tuple locks disappear after DELETE. The newer
      FOR UPDATE + single-CTE approach seems safer, though I wonder whether
      overlapping refreshes could still encounter deadlock scenarios around
      UPSERT conflicts.
      - The CONCURRENTLY behavior also feels somewhat unintuitive here. With
      WHERE refreshes, the non-CONCURRENT path appears more permissive for
      writers than CONCURRENTLY WHERE, which seems opposite to the expectation
      established by normal REFRESH MATERIALIZED VIEW semantics.
      - It may also help to document the intended guarantees around
      overlapping partial refreshes and concurrent DML on base tables.
   
   Overall, the use case seems quite valuable for selective high-churn refresh
   workloads.
   
   Thanks for working on this patch.
   
   Regards,
   
   Vellaipandiyan
   

2. Re: Review observations for partial REFRESH MATERIALIZED VIEW patc

   Andreas Karlsson <andreas@proxel.se> — 2026-05-19T09:59:54Z

   On 5/19/26 7:42 AM, vellaipandiyan sm wrote:
   > I reviewed the REFRESH MATERIALIZED VIEW ... WHERE patch and had a few 
   > questions around concurrency semantics.
   > 
   >   * The original DELETE -> INSERT approach exposing a consistency gap
   >     makes sense, especially once tuple locks disappear after DELETE. The
   >     newer FOR UPDATE + single-CTE approach seems safer, though I wonder
   >     whether overlapping refreshes could still encounter deadlock
   >     scenarios around UPSERT conflicts.
   >   * The CONCURRENTLY behavior also feels somewhat unintuitive here. With
   >     WHERE refreshes, the non-CONCURRENT path appears more permissive for
   >     writers than CONCURRENTLY WHERE, which seems opposite to the
   >     expectation established by normal REFRESH MATERIALIZED VIEW semantics.
   >   * It may also help to document the intended guarantees around
   >     overlapping partial refreshes and concurrent DML on base tables.
   
   Hi,
   
   Thanks for the review, but please reply-all to the original thread when 
   you review a patch so the original author and previous reviewers can see 
   your review.
   
   If you do not have the original email thread you can go into the archive 
   and request it to be sent to you so you can reply to it.
   
   You can click the "Resend email" link at 
   https://www.postgresql.org/message-id/CAA4eK1KSEL%2Bb81L47MpdVCY79n0QgboxF6XTEjSc0ZcLkDzyWQ%40mail.gmail.com
   
   -- 
   Andreas Karlsson
   Percona
   
   
   
   
   

3. Re: Review observations for partial REFRESH MATERIALIZED VIEW patc

   Andreas Karlsson <andreas@proxel.se> — 2026-05-19T10:04:39Z

   On 5/19/26 11:59 AM, Andreas Karlsson wrote:
   > You can click the "Resend email" link at https://www.postgresql.org/ 
   > message-id/ 
   > CAA4eK1KSEL%2Bb81L47MpdVCY79n0QgboxF6XTEjSc0ZcLkDzyWQ%40mail.gmail.com
   
   Sorry, somehow pasted the wrong link.
   
   https://www.postgresql.org/message-id/CAMjNa7d8f3sj-1ZsmsqiUPLzjXFtjOgeM7GFKvU_1EugyzJ5jw%40mail.gmail.com
   
   -- 
   Andreas Karlsson
   Percona