Improve error messages for some callers of XLogReadRecord()

A couple of code paths related to logical decoding (WAL sender, slot
advancing, etc.) use XLogReadRecord(), feeding on error messages
generated by walreader.c on a failure.  All those messages have no
context, making it harder to spot from where an error could come even if
these should not happen.  All the other callers of XLogReadRecord() do
that already.

Reviewed-by: Kyotaro Horiguchi
Discussion: https://postgr.es/m/[email protected]

4 files changed, 7 insertions, 5 deletions

diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index aae0ae5b8a..b7d9521576 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -605,9 +605,9 @@ DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
 		/* the read_page callback waits for new WAL */
 		record = XLogReadRecord(ctx->reader, &err);
 		if (err)
-			elog(ERROR, "%s", err);
+			elog(ERROR, "could not find logical decoding starting point: %s", err);
 		if (!record)
-			elog(ERROR, "no record found"); /* shouldn't happen */
+			elog(ERROR, "could not find logical decoding starting point");
 
 		LogicalDecodingProcessRecord(ctx, ctx->reader);
 
diff --git a/src/backend/replication/logical/logicalfuncs.c b/src/backend/replication/logical/logicalfuncs.c
index 2609a0a710..6cd2279a2e 100644
--- a/src/backend/replication/logical/logicalfuncs.c
+++ b/src/backend/replication/logical/logicalfuncs.c
@@ -276,7 +276,7 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
 
 			record = XLogReadRecord(ctx->reader, &errm);
 			if (errm)
-				elog(ERROR, "%s", errm);
+				elog(ERROR, "could not find record for logical decoding: %s", errm);
 
 			/*
 			 * The {begin_txn,change,commit_txn}_wrapper callbacks above will
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index a80298ba53..46175b7007 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -529,7 +529,8 @@ pg_logical_replication_slot_advance(XLogRecPtr moveto)
 			 */
 			record = XLogReadRecord(ctx->reader, &errm);
 			if (errm)
-				elog(ERROR, "%s", errm);
+				elog(ERROR, "could not find record while advancing replication slot: %s",
+					 errm);
 
 			/*
 			 * Process the record.  Storage-level changes are ignored in
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index fff7dfc640..7950afb173 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -2979,7 +2979,8 @@ XLogSendLogical(void)
 
 	/* xlog record was invalid */
 	if (errm != NULL)
-		elog(ERROR, "%s", errm);
+		elog(ERROR, "could not find record while sending logically-decoded data: %s",
+			 errm);
 
 	if (record != NULL)
 	{