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base repository: postgresql-cfbot/postgresql
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compare: cf/6319
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  • 2 commits
  • 2 files changed
  • 2 contributors

Commits on Dec 25, 2025

  1. Fix 'unexpected data beyond EOF' on replica restart 

    On restart, a replica can fail with an 'unexpected data beyond EOF in
block 200 of relation T/D/R' error. This can happen under the following
circumstances:

- A relation has a size of 400 blocks.
  - Blocks 201 to 400 are empty.
  - Block 200 has two rows.
  - Blocks 100 to 199 are empty.
- A restartpoint is done
- Vacuum truncates the relation to 200 blocks
- A FPW deletes a row in block 200
- A checkpoint is done
- A FPW deletes the last row in block 200
- Vacuum truncates the relation to 100 blocks
- The replica restarts

When the replica restarts:
- The relation on disk is reduced to 100 blocks due to having applied
  the truncate before restart.
- The first truncate to 200 blocks is replayed. It silently fails, but
  it will still update the cache size to 200 blocks
- The first FPW on block 200 is applied, XLogReadBufferForRead will rely
  on the cached size and incorrectly assume the page exists in file,
  and thus won't extend the relation.
- The Checkpoint Online is replayed, calling smgrdestroyall which will
  discard the cached size.
- The second FPW on block 200 is applied. This time, the detected size
  is 100 blocks, an extend is attempted. However, the block 200 is
  already present in the buffer table due to the first FPW. This
  triggers the 'unexpected data beyond EOF' since the page isn't new.

This patch fixes the issue by only updating smgr_cached_nblocks when
the truncated size is smaller. When the truncated size is higher, the
file isn't modified and we restore the old cached value.
    @bonnefoa
    bonnefoa authored and Commitfest Bot committed Dec 25, 2025
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  2. [CF 6319] v4 - Fix possible 'unexpected data beyond EOF' on replica r… 

    …estart

This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/6319

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
on the master branch.

Patch(es): https://www.postgresql.org/message-id/CAO6_XqrK-rpYnSfXP+sf=DdQR6ugO_p2W6Sw6XetmtqokeK3uA@mail.gmail.com
Author(s): Anthonin Bonnefoy
    Commitfest Bot committed Dec 25, 2025
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    9412996 View commit details
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