diff options
Diffstat (limited to 'src/backend/commands/vacuum.c')
| -rw-r--r-- | src/backend/commands/vacuum.c | 28 |
1 files changed, 16 insertions, 12 deletions
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c index 69ac276..68dce6a 100644 --- a/src/backend/commands/vacuum.c +++ b/src/backend/commands/vacuum.c @@ -1633,6 +1633,8 @@ vac_update_datfrozenxid(void) /* * We must seqscan pg_class to find the minimum Xid, because there is no * index that can help us here. + * + * See vac_truncate_clog() for the race condition to prevent. */ relation = table_open(RelationRelationId, AccessShareLock); @@ -1641,7 +1643,9 @@ vac_update_datfrozenxid(void) while ((classTup = systable_getnext(scan)) != NULL) { - Form_pg_class classForm = (Form_pg_class) GETSTRUCT(classTup); + volatile FormData_pg_class *classForm = (Form_pg_class) GETSTRUCT(classTup); + TransactionId relfrozenxid = classForm->relfrozenxid; + TransactionId relminmxid = classForm->relminmxid; /* * Only consider relations able to hold unfrozen XIDs (anything else @@ -1651,8 +1655,8 @@ vac_update_datfrozenxid(void) classForm->relkind != RELKIND_MATVIEW && classForm->relkind != RELKIND_TOASTVALUE) { - Assert(!TransactionIdIsValid(classForm->relfrozenxid)); - Assert(!MultiXactIdIsValid(classForm->relminmxid)); + Assert(!TransactionIdIsValid(relfrozenxid)); + Assert(!MultiXactIdIsValid(relminmxid)); continue; } @@ -1671,34 +1675,34 @@ vac_update_datfrozenxid(void) * before those relations have been scanned and cleaned up. */ - if (TransactionIdIsValid(classForm->relfrozenxid)) + if (TransactionIdIsValid(relfrozenxid)) { - Assert(TransactionIdIsNormal(classForm->relfrozenxid)); + Assert(TransactionIdIsNormal(relfrozenxid)); /* check for values in the future */ - if (TransactionIdPrecedes(lastSaneFrozenXid, classForm->relfrozenxid)) + if (TransactionIdPrecedes(lastSaneFrozenXid, relfrozenxid)) { bogus = true; break; } /* determine new horizon */ - if (TransactionIdPrecedes(classForm->relfrozenxid, newFrozenXid)) - newFrozenXid = classForm->relfrozenxid; + if (TransactionIdPrecedes(relfrozenxid, newFrozenXid)) + newFrozenXid = relfrozenxid; } - if (MultiXactIdIsValid(classForm->relminmxid)) + if (MultiXactIdIsValid(relminmxid)) { /* check for values in the future */ - if (MultiXactIdPrecedes(lastSaneMinMulti, classForm->relminmxid)) + if (MultiXactIdPrecedes(lastSaneMinMulti, relminmxid)) { bogus = true; break; } /* determine new horizon */ - if (MultiXactIdPrecedes(classForm->relminmxid, newMinMulti)) - newMinMulti = classForm->relminmxid; + if (MultiXactIdPrecedes(relminmxid, newMinMulti)) + newMinMulti = relminmxid; } } |