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Remove misleading hint for "unexpected data beyond EOF" error.

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Commit ffae5cc5a6 added this hint in 2006,
but it's now obsolete and doesn't reflect what users should really check
in this situation. We were not able to agree on a new hint, so just delete
the existing one and update the comments to mention one possibility that
is known to cause problems of this kind: something other than PostgreSQL
is modifying files in the PostgreSQL data directory.

Author: Jakub Wartak <jakub.wartak@enterprisedb.com>
Reviewed-by: Robert Haas <rhaas@postgresql.org>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Christoph Berg <myon@debian.org>
Discussion: https://postgr.es/m/CAKZiRmxNbcaL76x=09Sxf7aUmrRQJBf8drzDdUHo+j9_eM+VMg@mail.gmail.com
This commit is contained in:
Robert Haas
2025-07-28 11:15:47 -04:00
parent dcc9820a35
commit d5b9b2d402
1 changed files with 4 additions and 7 deletions
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11
src/backend/storage/buffer/bufmgr.c
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@ -2743,11 +2743,9 @@ ExtendBufferedRelShared(BufferManagerRelation bmr,
* because mdread doesn't complain about reads beyond EOF (when
* zero_damaged_pages is ON) and so a previous attempt to read a block
* beyond EOF could have left a "valid" zero-filled buffer.
* Unfortunately, we have also seen this case occurring because of
* buggy Linux kernels that sometimes return an lseek(SEEK_END) result
* that doesn't account for a recent write. In that situation, the
* pre-existing buffer would contain valid data that we don't want to
* overwrite. Since the legitimate cases should always have left a
*
* This has also been observed when relation was overwritten by external
* process. Since the legitimate cases should always have left a
* zero-filled buffer, complain if not PageIsNew.
*/
if (existing_id >= 0)
@ -2778,8 +2776,7 @@ ExtendBufferedRelShared(BufferManagerRelation bmr,
ereport(ERROR,
(errmsg("unexpected data beyond EOF in block %u of relation %s",
existing_hdr->tag.blockNum,
relpath(bmr.smgr->smgr_rlocator, fork).str),
errhint("This has been seen to occur with buggy kernels; consider updating your system.")));
relpath(bmr.smgr->smgr_rlocator, fork).str)));
/*
* We *must* do smgr[zero]extend before succeeding, else the page