v20240111-0006-add-comment-about-SNAPBUILD_FULL.patch
text/x-patch
Filename: v20240111-0006-add-comment-about-SNAPBUILD_FULL.patch
Type: text/x-patch
Part: 5
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Format: format-patch
Series: patch v20240111-0006
Subject: add comment about SNAPBUILD_FULL
| File | + | − |
|---|---|---|
| src/backend/replication/logical/decode.c | 16 | 1 |
From 2d96af7b89008d906ffc2a76ca906e0f7eac0a68 Mon Sep 17 00:00:00 2001 From: Tomas Vondra <tomas.vondra@postgresql.org> Date: Thu, 11 Jan 2024 14:35:29 +0100 Subject: [PATCH v20240111 6/7] add comment about SNAPBUILD_FULL --- src/backend/replication/logical/decode.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 3462c545bb7..95f224df4a7 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -1432,12 +1432,27 @@ seq_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * change as transactional and queue it. Otherwise it needs to be treated * as non-transactional, in which case we just send it to the plugin right * away. + * + * XXX This may incorrectly identify some changes as non-transactional, + * if the relfilenode was created before the snapshot switched to FULL + * (so that smgr_decode skipped it, and it's not in the hash table). + * But we still handle this correctly, because the snapshot can't be + * in CONSISTENT state yet, so the following check will skip the change + * too, and we won't try to apply it (which would fail due to unknown + * relfilenode). */ transactional = ReorderBufferSequenceIsTransactional(ctx->reorder, target_locator, NULL); - /* Skip the change if already processed (per the snapshot). */ + /* + * Skip the change if already processed (per the snapshot). + * + * XXX It's important to skip all non-transactional changes with snapshot + * that is not consistent yet. The sequence change may be incorrectly + * identified as non-transactional (see above), and we must not attempt + * to process it. + */ if (transactional && !SnapBuildProcessChange(builder, xid, buf->origptr)) return; -- 2.43.0