Improve subscriber's error message for wrong publication relkind.

Pre-v13 versions only support logical replication from plain tables,
while v13 and later also allow partitioned tables to be published.
If you tried to subscribe an older server to such a publication,
you got "table XXX not found on publisher", which is pretty
unhelpful/confusing.  Arrange to deliver a more on-point error
message.  As commit c314c147c did in v13, remove the relkind check
from the query WHERE clause altogether, so that "not there"
is distinguishable from "wrong relkind".

Per report from Radoslav Nedyalkov.  Patch v10-v12.

Discussion: https://postgr.es/m/2952568.1644876730@sss.pgh.pa.us

1 files changed, 17 insertions, 4 deletions

diff --git a/src/backend/replication/logical/tablesync.c b/src/backend/replication/logical/tablesync.c
index 14f69a6338e..b9fea15739e 100644
--- a/src/backend/replication/logical/tablesync.c
+++ b/src/backend/replication/logical/tablesync.c
@@ -659,9 +659,10 @@ fetch_remote_table_info(char *nspname, char *relname,
 	WalRcvExecResult *res;
 	StringInfoData cmd;
 	TupleTableSlot *slot;
-	Oid			tableRow[2] = {OIDOID, CHAROID};
+	Oid			tableRow[3] = {OIDOID, CHAROID, CHAROID};
 	Oid			attrRow[4] = {TEXTOID, OIDOID, INT4OID, BOOLOID};
 	bool		isnull;
+	char		relkind;
 	int			natt;
 
 	lrel->nspname = nspname;
@@ -669,13 +670,12 @@ fetch_remote_table_info(char *nspname, char *relname,
 
 	/* First fetch Oid and replica identity. */
 	initStringInfo(&cmd);
-	appendStringInfo(&cmd, "SELECT c.oid, c.relreplident"
+	appendStringInfo(&cmd, "SELECT c.oid, c.relreplident, c.relkind"
 					 "  FROM pg_catalog.pg_class c"
 					 "  INNER JOIN pg_catalog.pg_namespace n"
 					 "        ON (c.relnamespace = n.oid)"
 					 " WHERE n.nspname = %s"
-					 "   AND c.relname = %s"
-					 "   AND c.relkind = 'r'",
+					 "   AND c.relname = %s",
 					 quote_literal_cstr(nspname),
 					 quote_literal_cstr(relname));
 	res = walrcv_exec(LogRepWorkerWalRcvConn, cmd.data,
@@ -696,6 +696,19 @@ fetch_remote_table_info(char *nspname, char *relname,
 	Assert(!isnull);
 	lrel->replident = DatumGetChar(slot_getattr(slot, 2, &isnull));
 	Assert(!isnull);
+	relkind = DatumGetChar(slot_getattr(slot, 3, &isnull));
+	Assert(!isnull);
+
+	/*
+	 * Newer PG versions allow things that aren't plain tables to appear in
+	 * publications.  We don't handle that in this version, but try to provide
+	 * a useful error message.
+	 */
+	if (relkind != RELKIND_RELATION)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("logical replication source relation \"%s.%s\" is not a table",
+						nspname, relname)));
 
 	ExecDropSingleTupleTableSlot(slot);
 	walrcv_clear_result(res);