Fix MVCC bug with prepared xact with subxacts on standby #8152
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1a69cc2 at 2024-06-25T12:08:31.507Z :recycle: |
We did not recover the subtransaction IDs of prepared transactions when starting a hot standby from a shutdown checkpoint. As a result, such subtransactions were considered as aborted, rather than in-progress. That would lead to hint bits being set incorrectly, and the subtransactions suddenly becoming visible to old snapshots when the prepared transaction was committed. To fix, update pg_subtrans with prepared transactions's subxids when starting hot standby from a shutdown checkpoint. The snapshots taken from that state need to be marked as "suboverflowed", so that we also check the pg_subtrans. Discussion: https://www.postgresql.org/message-id/6b852e98-2d49-4ca1-9e95-db419a2696e0%40iki.fi NEON: cherry-picked from the upstream thread ahead of time, to unblock #7288. I expect this to be committed to upstream in the next few days, superseding this. NOTE: I did not include the new regression test on v15 and v14 branches, because the test would need some adapting, and we don't run the perl tests on Neon anyway.
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This was referenced Jun 25, 2024
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Corresponding PRs in the postgres repo: |
knizhnik
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Jun 25, 2024
Changed base for #449 and approved all Postgres PRs |
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@hlinnaka |
Ah, thanks. I think I used the "Rebase and merge" button on the postgres branches, which changed the commit SHAs. |
jcsp
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We did not recover the subtransaction IDs of prepared transactions when starting a hot standby from a shutdown checkpoint. As a result, such subtransactions were considered as aborted, rather than in-progress. That would lead to hint bits being set incorrectly, and the subtransactions suddenly becoming visible to old snapshots when the prepared transaction was committed. To fix, update pg_subtrans with prepared transactions's subxids when starting hot standby from a shutdown checkpoint. The snapshots taken from that state need to be marked as "suboverflowed", so that we also check the pg_subtrans. Discussion: https://www.postgresql.org/message-id/6b852e98-2d49-4ca1-9e95-db419a2696e0%40iki.fi NEON: cherry-picked from the upstream thread ahead of time, to unblock #7288. I expect this to be committed to upstream in the next few days, superseding this. NOTE: I did not include the new regression test on v15 and v14 branches, because the test would need some adapting, and we don't run the perl tests on Neon anyway.
conradludgate
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We did not recover the subtransaction IDs of prepared transactions when starting a hot standby from a shutdown checkpoint. As a result, such subtransactions were considered as aborted, rather than in-progress. That would lead to hint bits being set incorrectly, and the subtransactions suddenly becoming visible to old snapshots when the prepared transaction was committed. To fix, update pg_subtrans with prepared transactions's subxids when starting hot standby from a shutdown checkpoint. The snapshots taken from that state need to be marked as "suboverflowed", so that we also check the pg_subtrans. Discussion: https://www.postgresql.org/message-id/6b852e98-2d49-4ca1-9e95-db419a2696e0%40iki.fi NEON: cherry-picked from the upstream thread ahead of time, to unblock #7288. I expect this to be committed to upstream in the next few days, superseding this. NOTE: I did not include the new regression test on v15 and v14 branches, because the test would need some adapting, and we don't run the perl tests on Neon anyway.
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We did not recover the subtransaction IDs of prepared transactions when starting a hot standby from a shutdown checkpoint. As a result, such subtransactions were considered as aborted, rather than in-progress. That would lead to hint bits being set incorrectly, and the subtransactions suddenly becoming visible to old snapshots when the prepared transaction was committed.
To fix, update pg_subtrans with prepared transactions's subxids when starting hot standby from a shutdown checkpoint. The snapshots taken from that state need to be marked as "suboverflowed", so that we also check the pg_subtrans.
Discussion: https://www.postgresql.org/message-id/6b852e98-2d49-4ca1-9e95-db419a2696e0%40iki.fi
NEON: cherry-picked from the upstream thread ahead of time, to unblock #7288. I expect this to be committed to upstream in the next few days, superseding this. NOTE: I did not include the new regression test on v15 and v14 branches, because the test would need some adapting, and we don't run the perl tests on Neon anyway.