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Diffstat (limited to 'src/backend/access/transam/varsup.c')
| -rw-r--r-- | src/backend/access/transam/varsup.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c index 2d2b05be36c..a4944faa32e 100644 --- a/src/backend/access/transam/varsup.c +++ b/src/backend/access/transam/varsup.c @@ -367,12 +367,13 @@ SetTransactionIdLimit(TransactionId oldest_datfrozenxid, Oid oldest_datoid) * We'll refuse to continue assigning XIDs in interactive mode once we get * within 3M transactions of data loss. This leaves lots of room for the * DBA to fool around fixing things in a standalone backend, while not - * being significant compared to total XID space. (Note that since - * vacuuming requires one transaction per table cleaned, we had better be - * sure there's lots of XIDs left...) Also, at default BLCKSZ, this - * leaves two completely-idle segments. In the event of edge-case bugs - * involving page or segment arithmetic, idle segments render the bugs - * unreachable outside of single-user mode. + * being significant compared to total XID space. (VACUUM requires an XID + * if it truncates at wal_level!=minimal. "VACUUM (ANALYZE)", which a DBA + * might do by reflex, assigns an XID. Hence, we had better be sure + * there's lots of XIDs left...) Also, at default BLCKSZ, this leaves two + * completely-idle segments. In the event of edge-case bugs involving + * page or segment arithmetic, idle segments render the bugs unreachable + * outside of single-user mode. */ xidStopLimit = xidWrapLimit - 3000000; if (xidStopLimit < FirstNormalTransactionId) |