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From: Alvaro Herrera <[email protected]>
Subject: [PATCH v3] decode XACT_ASSIGNMENT while building snapshot
Date: Fri, 26 Jul 2019 18:38:44 -0400

---
 src/backend/replication/logical/decode.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index 151c3ef882..a6f7dc2723 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -215,14 +215,19 @@ DecodeXactOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 	ReorderBuffer *reorder = ctx->reorder;
 	XLogReaderState *r = buf->record;
 	uint8		info = XLogRecGetInfo(r) & XLOG_XACT_OPMASK;
+	SnapBuildState state;
 
 	/*
-	 * No point in doing anything yet, data could not be decoded anyway. It's
-	 * ok not to call ReorderBufferProcessXid() in that case, except in the
-	 * assignment case there'll not be any later records with the same xid;
-	 * and in the assignment case we'll not decode those xacts.
+	 * If the snapshot isn't yet fully built, we cannot decode anything, so
+	 * bail out.
+	 *
+	 * However, it's critical to process XLOG_XACT_ASSIGNMENT records even
+	 * when the snapshot is being built: it is possible to get later records
+	 * that require subxids to be properly assigned.
 	 */
-	if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT)
+	state = SnapBuildCurrentState(builder);
+	if (state < SNAPBUILD_FULL_SNAPSHOT ||
+		(info == XLOG_XACT_ASSIGNMENT && state < SNAPBUILD_BUILDING_SNAPSHOT))
 		return;
 
 	switch (info)
-- 
2.17.1


--3MwIy2ne0vdjdPXF--





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