> On Apr 16, 2026, at 14:13, SATYANARAYANA NARLAPURAM
> <[email protected]> wrote:
>
> Hi hackers,
>
> restore_tuple() in repack.c uses SET_VARSIZE() to reconstruct the varlena
> header when
> reading back external attributes from the spill file. In this process, looks
> like the flag
> SET_VARSIZE_COMPRESSED is silently lost. Because of this, when REPACK
> CONCURRENTLY
> run any concurrently updated column whose value was TOAST-compressed ends up
> with raw
> compressed bytes behind an "uncompressed" header returning garbled data on
> subsequent reads.
> It appears that existing tests are using random chars which are
> uncompressable.
>
> Please find the attached
> 0001-Fix-restore_tuple-losing-varlena-compression-flag.patch to fix this.
> Additionally I updated the existing repack_toast test to include the scenario
> I was talking about.
>
> Thanks,
> Satya
> <0001-Fix-restore_tuple-losing-varlena-compression-flag.patch><0002-Add-compressed-TOAST-test-to-repack_toast.patch>
I managed to reproduce the bug manually, and confirmed your fix to work for me.
The repro is not simple, so I won’t put it here. If somebody is interested in
it, then I can provide.
I didn’t review the test in 0002, I guess we don’t have to add the test because
once fixed, the bug won’t be there anymore, thus it’s not worthy extending the
test time.
Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/
