From 6daeeb1f9196e5d59aa7d5c9ef7ed67b3f3ac4b5 Mon Sep 17 00:00:00 2001 From: Peter Geoghegan Date: Mon, 2 Jan 2023 10:16:51 -0800 Subject: [PATCH] Avoid special XID snapshotConflictHorizon values. Don't allow VACUUM to WAL-log the value FrozenTransactionId as the snapshotConflictHorizon of freezing or visibility map related WAL records. The only special XID value that's an allowable snapshotConflictHorizon is InvalidTransactionId, which is interpreted as "record definitely doesn't require a recovery conflict". Author: Peter Geoghegan Discussion: https://postgr.es/m/CAH2-WznuNGSzF8v6OsgjaC5aYsb3cZ6HW6MLm30X0d65cmSH6A@mail.gmail.com --- src/backend/access/heap/vacuumlazy.c | 8 +++++--- src/backend/storage/ipc/standby.c | 1 + 2 files changed, 6 insertions(+), 3 deletions(-) diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c index 9923994b50..5d8fd2fb72 100644 --- a/src/backend/access/heap/vacuumlazy.c +++ b/src/backend/access/heap/vacuumlazy.c @@ -1698,7 +1698,8 @@ retry: } /* Track newest xmin on page. */ - if (TransactionIdFollows(xmin, prunestate->visibility_cutoff_xid)) + if (TransactionIdFollows(xmin, prunestate->visibility_cutoff_xid) && + TransactionIdIsNormal(xmin)) prunestate->visibility_cutoff_xid = xmin; } break; @@ -1863,7 +1864,7 @@ retry: * because visibility_cutoff_xid will be logged by our caller in a * moment. */ - Assert(cutoff == FrozenTransactionId || + Assert(!TransactionIdIsValid(cutoff) || cutoff == prunestate->visibility_cutoff_xid); } #endif @@ -3293,7 +3294,8 @@ heap_page_is_all_visible(LVRelState *vacrel, Buffer buf, } /* Track newest xmin on page. */ - if (TransactionIdFollows(xmin, *visibility_cutoff_xid)) + if (TransactionIdFollows(xmin, *visibility_cutoff_xid) && + TransactionIdIsNormal(xmin)) *visibility_cutoff_xid = xmin; /* Check whether this tuple is already frozen or not */ diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index f43229dfda..ede00fee93 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -493,6 +493,7 @@ ResolveRecoveryConflictWithSnapshot(TransactionId snapshotConflictHorizon, if (!TransactionIdIsValid(snapshotConflictHorizon)) return; + Assert(TransactionIdIsNormal(snapshotConflictHorizon)); backends = GetConflictingVirtualXIDs(snapshotConflictHorizon, locator.dbOid); ResolveRecoveryConflictWithVirtualXIDs(backends,