diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index c5de2040f7..1acf75be6f 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -134,12 +134,12 @@
    to replica identity <literal>FULL</literal>, which means the entire row becomes
    the key.  When replica identity <literal>FULL</literal> is specified,
    indexes can be used on the subscriber side for searching the rows.  Candidate
-   indexes must be btree, non-partial, and have at least one column reference
-   (i.e. cannot consist of only expressions).  These restrictions
-   on the non-unique index properties adhere to some of the restrictions that
-   are enforced for primary keys.  If there are no such suitable indexes,
-   the search on the subscriber side can be very inefficient, therefore
-   replica identity <literal>FULL</literal> should only be used as a
+   indexes must be btree, non-partial, and have at least one column reference to
+   the published table column at the leftmost column (i.e. cannot consist of only
+   expressions).  These restrictions on the non-unique index properties adhere to
+   some of the restrictions that are enforced for primary keys.  If there are no
+   such suitable indexes, the search on the subscriber side can be very inefficient,
+   therefore replica identity <literal>FULL</literal> should only be used as a
    fallback if no other solution is possible.  If a replica identity other
    than <literal>FULL</literal> is set on the publisher side, a replica identity
    comprising the same or fewer columns must also be set on the subscriber
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index 9dd7168461..6f2a465133 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -47,9 +47,9 @@ static bool tuples_equal(TupleTableSlot *slot1, TupleTableSlot *slot2,
  *
  * Returns how many columns to use for the index scan.
  *
- * This is not generic routine, it expects the idxrel to be a btree, non-partial
- * and have at least one column reference (i.e. cannot consist of only
- * expressions).
+ * This is not generic routine, idxrel must be PK, RI, or an index that can be
+ * used for REPLICA IDENTITY FULL table (see FindUsableIndexForReplicaIdentityFull()
+ * for details).
  *
  * By definition, replication identity of a rel meets all limitations associated
  * with that. Note that any other index could also meet these limitations.
diff --git a/src/backend/replication/logical/relation.c b/src/backend/replication/logical/relation.c
index 57ad22b48a..ce66149b5e 100644
--- a/src/backend/replication/logical/relation.c
+++ b/src/backend/replication/logical/relation.c
@@ -780,8 +780,9 @@ RemoteRelContainsLeftMostColumnOnIdx(IndexInfo *indexInfo, AttrMap *attrmap)
 /*
  * Returns the oid of an index that can be used by the apply worker to scan
  * the relation. The index must be btree, non-partial, and have at least
- * one column reference (i.e. cannot consist of only expressions). These
- * limitations help to keep the index scan similar to PK/RI index scans.
+ * one column reference to the remote relation's column at the leftmost column
+ * (i.e. cannot consist of only expressions). These limitations help to keep the
+ * index scan similar to PK/RI index scans.
  *
  * Note that the limitations of index scans for replica identity full only
  * adheres to a subset of the limitations of PK/RI. For example, we support