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Diffstat (limited to 'src/backend/access/transam/subtrans.c')
| -rw-r--r-- | src/backend/access/transam/subtrans.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c index 4bc24d9bbcb..6b709823227 100644 --- a/src/backend/access/transam/subtrans.c +++ b/src/backend/access/transam/subtrans.c @@ -340,8 +340,13 @@ TruncateSUBTRANS(TransactionId oldestXact) /* * The cutoff point is the start of the segment containing oldestXact. We - * pass the *page* containing oldestXact to SimpleLruTruncate. + * pass the *page* containing oldestXact to SimpleLruTruncate. We step + * back one transaction to avoid passing a cutoff page that hasn't been + * created yet in the rare case that oldestXact would be the first item on + * a page and oldestXact == next XID. In that case, if we didn't subtract + * one, we'd trigger SimpleLruTruncate's wraparound detection. */ + TransactionIdRetreat(oldestXact); cutoffPage = TransactionIdToPage(oldestXact); SimpleLruTruncate(SubTransCtl, cutoffPage); |