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Avoid repeating loads of frozen ID values.

Browse Source 
Repeating loads of inplace-updated fields tends to cause bugs like the
one from the previous commit.  While there's no bug to fix in these code
sites, adopt the load-once style.  This improves the chance of future
copy/paste finding the safe style.

Discussion: https://postgr.es/m/20240423003956.e7.nmisch@google.com
This commit is contained in:
Noah Misch
2024-04-29 10:25:33 -07:00
parent f65ab862e3
commit dd0183469b
4 changed files with 34 additions and 21 deletions
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22
src/backend/commands/cluster.c
View File

@@ -919,18 +919,24 @@ copy_table_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex, bool verbose,
* FreezeXid will become the table's new relfrozenxid, and that mustn't go
* backwards, so take the max.
*/
if (TransactionIdIsValid(OldHeap->rd_rel->relfrozenxid) &&
TransactionIdPrecedes(cutoffs.FreezeLimit,
OldHeap->rd_rel->relfrozenxid))
cutoffs.FreezeLimit = OldHeap->rd_rel->relfrozenxid;
{
TransactionId relfrozenxid = OldHeap->rd_rel->relfrozenxid;
if (TransactionIdIsValid(relfrozenxid) &&
TransactionIdPrecedes(cutoffs.FreezeLimit, relfrozenxid))
cutoffs.FreezeLimit = relfrozenxid;
}
/*
* MultiXactCutoff, similarly, shouldn't go backwards either.
*/
if (MultiXactIdIsValid(OldHeap->rd_rel->relminmxid) &&
MultiXactIdPrecedes(cutoffs.MultiXactCutoff,
OldHeap->rd_rel->relminmxid))
cutoffs.MultiXactCutoff = OldHeap->rd_rel->relminmxid;
{
MultiXactId relminmxid = OldHeap->rd_rel->relminmxid;
if (MultiXactIdIsValid(relminmxid) &&
MultiXactIdPrecedes(cutoffs.MultiXactCutoff, relminmxid))
cutoffs.MultiXactCutoff = relminmxid;
}
/*
* Decide whether to use an indexscan or seqscan-and-optional-sort to scan

4
src/backend/commands/vacuum.c
View File

@@ -1200,7 +1200,7 @@ vacuum_get_cutoffs(Relation rel, const VacuumParams *params,
aggressiveXIDCutoff = nextXID - freeze_table_age;
if (!TransactionIdIsNormal(aggressiveXIDCutoff))
aggressiveXIDCutoff = FirstNormalTransactionId;
if (TransactionIdPrecedesOrEquals(rel->rd_rel->relfrozenxid,
if (TransactionIdPrecedesOrEquals(cutoffs->relfrozenxid,
aggressiveXIDCutoff))
return true;
@@ -1221,7 +1221,7 @@ vacuum_get_cutoffs(Relation rel, const VacuumParams *params,
aggressiveMXIDCutoff = nextMXID - multixact_freeze_table_age;
if (aggressiveMXIDCutoff < FirstMultiXactId)
aggressiveMXIDCutoff = FirstMultiXactId;
if (MultiXactIdPrecedesOrEquals(rel->rd_rel->relminmxid,
if (MultiXactIdPrecedesOrEquals(cutoffs->relminmxid,
aggressiveMXIDCutoff))
return true;