From 949ac32e12674d9c0bcd3d95ea5e56338a567a18 Mon Sep 17 00:00:00 2001 From: Tomas Vondra Date: Wed, 22 Feb 2023 15:24:09 +0100 Subject: Fix snapshot handling in logicalmsg_decode Whe decoding a transactional logical message, logicalmsg_decode called SnapBuildGetOrBuildSnapshot. But we may not have a consistent snapshot yet at that point. We don't actually need the snapshot in this case (during replay we'll have the snapshot from the transaction), so in practice this is harmless. But in assert-enabled build this crashes. Fixed by requesting the snapshot only in non-transactional case, where we are guaranteed to have SNAPBUILD_CONSISTENT. Backpatch to 11. The issue exists since 9.6. Backpatch-through: 11 Reviewed-by: Andres Freund Discussion: https://postgr.es/m/84d60912-6eab-9b84-5de3-41765a5449e8@enterprisedb.com --- src/backend/replication/logical/reorderbuffer.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'src/backend/replication/logical/reorderbuffer.c') diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c index e3b67e4447a..b1882ae5ecf 100644 --- a/src/backend/replication/logical/reorderbuffer.c +++ b/src/backend/replication/logical/reorderbuffer.c @@ -828,6 +828,13 @@ ReorderBufferQueueMessage(ReorderBuffer *rb, TransactionId xid, Assert(xid != InvalidTransactionId); + /* + * We don't expect snapshots for transactional changes - we'll use the + * snapshot derived later during apply (unless the change gets + * skipped). + */ + Assert(!snapshot); + oldcontext = MemoryContextSwitchTo(rb->context); change = ReorderBufferGetChange(rb); @@ -846,6 +853,9 @@ ReorderBufferQueueMessage(ReorderBuffer *rb, TransactionId xid, ReorderBufferTXN *txn = NULL; volatile Snapshot snapshot_now = snapshot; + /* Non-transactional changes require a valid snapshot. */ + Assert(snapshot_now); + if (xid != InvalidTransactionId) txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true); -- cgit v1.2.3