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Set ReorderBufferTXN->final_lsn more eagerly

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... specifically, set it incrementally as each individual change is
spilled down to disk.  This way, it is set correctly when the
transaction disappears without trace, ie. without leaving an XACT_ABORT
wal record.  (This happens when the server crashes midway through a
transaction.)

Failing to have final_lsn prevents ReorderBufferRestoreCleanup() from
working, since it needs the final_lsn in order to know the endpoint of
its iteration through spilled files.

Commit df9f682c7bf8 already tried to fix the problem, but it didn't set
the final_lsn in all cases.  Revert that, since it's no longer needed.

Author: Vignesh C
Reviewed-by: Amit Kapila, Dilip Kumar
Discussion: https://postgr.es/m/CALDaNm2CLk+K9JDwjYST0sPbGg5AQdvhUt0jbKyX_HdAE0jk3A@mail.gmail.com
This commit is contained in:
Alvaro Herrera 2020-01-17 18:00:39 -03:00
parent 543852fd8b
commit 15cac3a523
2 changed files with 16 additions and 20 deletions
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29
src/backend/replication/logical/reorderbuffer.c
View File

@ -1974,21 +1974,6 @@ ReorderBufferAbortOld(ReorderBuffer *rb, TransactionId oldestRunningXid)
if (TransactionIdPrecedes(txn->xid, oldestRunningXid)) if (TransactionIdPrecedes(txn->xid, oldestRunningXid))
{ {
/*
* We set final_lsn on a transaction when we decode its commit or
* abort record, but we never see those records for crashed
* transactions. To ensure cleanup of these transactions, set
* final_lsn to that of their last change; this causes
* ReorderBufferRestoreCleanup to do the right thing.
*/
if (rbtxn_is_serialized(txn) && txn->final_lsn == 0)
{
ReorderBufferChange *last =
dlist_tail_element(ReorderBufferChange, node, &txn->changes);
txn->final_lsn = last->lsn;
}
elog(DEBUG2, "aborting old transaction %u", txn->xid); elog(DEBUG2, "aborting old transaction %u", txn->xid);
/* remove potential on-disk data, and deallocate this tx */ /* remove potential on-disk data, and deallocate this tx */
@ -2623,8 +2608,7 @@ ReorderBufferSerializeChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
sz += sizeof(SnapshotData) + sz += sizeof(SnapshotData) +
sizeof(TransactionId) * snap->xcnt + sizeof(TransactionId) * snap->xcnt +
sizeof(TransactionId) * snap->subxcnt sizeof(TransactionId) * snap->subxcnt;
;
/* make sure we have enough space */ /* make sure we have enough space */
ReorderBufferSerializeReserve(rb, sz); ReorderBufferSerializeReserve(rb, sz);
@ -2697,6 +2681,17 @@ ReorderBufferSerializeChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
} }
pgstat_report_wait_end(); pgstat_report_wait_end();
/*
* Keep the transaction's final_lsn up to date with each change we send to
* disk, so that ReorderBufferRestoreCleanup works correctly. (We used to
* only do this on commit and abort records, but that doesn't work if a
* system crash leaves a transaction without its abort record).
*
* Make sure not to move it backwards.
*/
if (txn->final_lsn < change->lsn)
txn->final_lsn = change->lsn;
Assert(ondisk->change.action == change->action); Assert(ondisk->change.action == change->action);
} }

7
src/include/replication/reorderbuffer.h
View File

@ -207,9 +207,10 @@ typedef struct ReorderBufferTXN
* * prepared transaction commit * * prepared transaction commit
* * plain abort record * * plain abort record
* * prepared transaction abort * * prepared transaction abort
* * error during decoding *
* * for a crashed transaction, the LSN of the last change, regardless of * This can also become set to earlier values than transaction end when
* what it was. * a transaction is spilled to disk; specifically it's set to the LSN of
* the latest change written to disk so far.
* ---- * ----
*/ */
XLogRecPtr final_lsn; XLogRecPtr final_lsn;