Re: Issues with ON CONFLICT UPDATE and REINDEX CONCURRENTLY

Noah Misch <noah@leadboat.com>

From: Noah Misch <noah@leadboat.com>

To: Mihail Nikalayeu <mihailnikalayeu@gmail.com>

Cc: Michael Paquier <michael@paquier.xyz>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>

Date: 2025-11-02T23:21:05Z

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 →

Replace flaky CIC/RI isolation tests with a TAP test
- e1c971945d62 19 (unreleased) landed
Disable recently added CIC/RI isolation tests
- 77038d6d0b49 19 (unreleased) landed
Fix infer_arbiter_index for partitioned tables
- 81f72115cf18 19 (unreleased) landed
Stabilize tests some more
- a4a0fa0c7587 19 (unreleased) landed
Put back alternative-output expected files
- be25c7767728 19 (unreleased) landed
Remove doc and code comments about ON CONFLICT deficiencies
- 758479213d57 19 (unreleased) landed
Avoid use of NOTICE to wait for snapshot invalidation
- 5dee7a603f66 19 (unreleased) landed
Fix ON CONFLICT with REINDEX CONCURRENTLY and partitions
- 90eae926abbb 19 (unreleased) landed
Fix ON CONFLICT ON CONSTRAINT during REINDEX CONCURRENTLY
- 2bc7e886fc1b 19 (unreleased) landed
Fix new test for CATCACHE_FORCE_RELEASE builds
- 9e8fa05d3412 19 (unreleased) landed
Improve test case stability
- 417ac9c1eeeb 19 (unreleased) landed
Fix infer_arbiter_index during concurrent index operations
- bc32a12e0db2 19 (unreleased) landed
Doc: cover index CONCURRENTLY causing errors in INSERT ... ON CONFLICT.
- 438ccd33a37a 13.23 landed
- faba2595d619 14.20 landed
- e1dd1f924e19 15.15 landed
- 4c2895629f6f 16.11 landed
- 46524d519a2d 18.1 landed
- 27f714b5dad7 17.7 landed
- 8b18ed6dfbb8 19 (unreleased) landed
Fix infer_arbiter_indexes() to not assume resultRelation is 1.
- 915de706d28c 17.0 cited
Revert temporal primary keys and foreign keys
- 8aee330af55d 17.0 cited

Attachments

doc-concurrently-on-conflict-v2nm.patch (text/plain) patch

On Tue, Oct 28, 2025 at 02:19:00AM +0100, Mihail Nikalayeu wrote:
> On Mon, Oct 27, 2025 at 7:06 PM Noah Misch <noah@leadboat.com> wrote:
> > Yes, I'm happy to push a patch documenting it.  Would you like to propose the
> > specific doc patch?  I regret lacking the bandwidth to review the fix patches.
> 
> Of course!
> 
> First version in attachment, waiting for your comment.

Thanks.  Does "ON CONFLICT ON CONSTRAINT constraint_name" avoid the problem w/
concurrent REINDEX CONCURRENTLY?  A search of the thread found no mention of
"ON CONSTRAINT".  It seems safe to assume that clause would avoid problems w/
CREATE INDEX CONCURRENTLY, but that's less certain for REINDEX.

The attached version has these changes:

- Mention ON CONSTRAINT as a workaround.  Will remove if you find or suspect
  it's not effective.
- Limit the doc change to ON CONFLICT.  I think mentioning it at the INDEX
  commands is undue emphasis.
- Use term "unique violation", a term used earlier on the same page, instead
  of "duplicate key ...".
- Remove the internals-focused point about the brief window.
- Remove some detail I considered insufficiently surprising, e.g. the point
  about "compatible with the index being built".