diff options
Diffstat (limited to 'src/backend/commands/sequence.c')
| -rw-r--r-- | src/backend/commands/sequence.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c index 9404efa379f..84ac3a0d0f7 100644 --- a/src/backend/commands/sequence.c +++ b/src/backend/commands/sequence.c @@ -950,6 +950,22 @@ read_info(SeqTable elm, Relation rel, Buffer *buf) Assert(ItemIdIsUsed(lp)); tuple.t_data = (HeapTupleHeader) PageGetItem((Page) page, lp); + /* + * Previous releases of Postgres neglected to prevent SELECT FOR UPDATE + * on a sequence, which would leave a non-frozen XID in the sequence + * tuple's xmax, which eventually leads to clog access failures or worse. + * If we see this has happened, clean up after it. We treat this like a + * hint bit update, ie, don't bother to WAL-log it, since we can certainly + * do this again if the update gets lost. + */ + if (HeapTupleHeaderGetXmax(tuple.t_data) != InvalidTransactionId) + { + HeapTupleHeaderSetXmax(tuple.t_data, InvalidTransactionId); + tuple.t_data->t_infomask &= ~HEAP_XMAX_COMMITTED; + tuple.t_data->t_infomask |= HEAP_XMAX_INVALID; + SetBufferCommitInfoNeedsSave(*buf); + } + seq = (Form_pg_sequence) GETSTRUCT(&tuple); elm->increment = seq->increment_by; |