From 91c20ecb45a8627a9252ed589fe6b85927be8b45 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Thu, 25 Mar 2021 11:59:13 +0100
Subject: [PATCH 2/6] fixup! Row filter for logical replication

Allow replication from older PostgreSQL versions without prqual.
---
 src/backend/replication/logical/tablesync.c | 70 +++++++++++----------
 1 file changed, 37 insertions(+), 33 deletions(-)

diff --git a/src/backend/replication/logical/tablesync.c b/src/backend/replication/logical/tablesync.c
index 40d84dadb5..246510c82e 100644
--- a/src/backend/replication/logical/tablesync.c
+++ b/src/backend/replication/logical/tablesync.c
@@ -796,49 +796,53 @@ fetch_remote_table_info(char *nspname, char *relname,
 	walrcv_clear_result(res);
 
 	/* Get relation qual */
-	resetStringInfo(&cmd);
-	appendStringInfo(&cmd,
-					 "SELECT pg_get_expr(prqual, prrelid) "
-					 "  FROM pg_publication p "
-					 "  INNER JOIN pg_publication_rel pr "
-					 "       ON (p.oid = pr.prpubid) "
-					 " WHERE pr.prrelid = %u "
-					 "   AND p.pubname IN (", lrel->remoteid);
-
-	first = true;
-	foreach(lc, MySubscription->publications)
+	if (walrcv_server_version(wrconn) >= 140000)
 	{
-		char	   *pubname = strVal(lfirst(lc));
+		resetStringInfo(&cmd);
+		appendStringInfo(&cmd,
+						 "SELECT pg_get_expr(prqual, prrelid) "
+						 "  FROM pg_publication p "
+						 "  INNER JOIN pg_publication_rel pr "
+						 "       ON (p.oid = pr.prpubid) "
+						 " WHERE pr.prrelid = %u "
+						 "   AND p.pubname IN (", lrel->remoteid);
+
+		first = true;
+		foreach(lc, MySubscription->publications)
+		{
+			char	   *pubname = strVal(lfirst(lc));
 
-		if (first)
-			first = false;
-		else
-			appendStringInfoString(&cmd, ", ");
+			if (first)
+				first = false;
+			else
+				appendStringInfoString(&cmd, ", ");
 
-		appendStringInfoString(&cmd, quote_literal_cstr(pubname));
-	}
-	appendStringInfoChar(&cmd, ')');
+			appendStringInfoString(&cmd, quote_literal_cstr(pubname));
+		}
+		appendStringInfoChar(&cmd, ')');
 
-	res = walrcv_exec(wrconn, cmd.data, 1, qualRow);
+		res = walrcv_exec(wrconn, cmd.data, 1, qualRow);
 
-	if (res->status != WALRCV_OK_TUPLES)
-		ereport(ERROR,
-				(errmsg("could not fetch relation qualifications for table \"%s.%s\" from publisher: %s",
-						nspname, relname, res->err)));
+		if (res->status != WALRCV_OK_TUPLES)
+			ereport(ERROR,
+					(errmsg("could not fetch relation qualifications for table \"%s.%s\" from publisher: %s",
+							nspname, relname, res->err)));
 
-	slot = MakeSingleTupleTableSlot(res->tupledesc, &TTSOpsMinimalTuple);
-	while (tuplestore_gettupleslot(res->tuplestore, true, false, slot))
-	{
-		Datum		rf = slot_getattr(slot, 1, &isnull);
+		slot = MakeSingleTupleTableSlot(res->tupledesc, &TTSOpsMinimalTuple);
+		while (tuplestore_gettupleslot(res->tuplestore, true, false, slot))
+		{
+			Datum		rf = slot_getattr(slot, 1, &isnull);
 
-		if (!isnull)
-			*qual = lappend(*qual, makeString(TextDatumGetCString(rf)));
+			if (!isnull)
+				*qual = lappend(*qual, makeString(TextDatumGetCString(rf)));
 
-		ExecClearTuple(slot);
+			ExecClearTuple(slot);
+		}
+		ExecDropSingleTupleTableSlot(slot);
+
+		walrcv_clear_result(res);
 	}
-	ExecDropSingleTupleTableSlot(slot);
 
-	walrcv_clear_result(res);
 	pfree(cmd.data);
 }
 
-- 
2.30.2