*** a/src/backend/commands/matview.c
--- b/src/backend/commands/matview.c
***************
*** 217,222 **** ExecRefreshMatView(RefreshMatViewStmt *stmt, const char *queryString,
--- 217,267 ----
  			 RelationGetRelationName(matviewRel));
  
  	/*
+ 	 * Check that there is a unique index with no WHERE clause on
+ 	 * one or more columns of the materialized view if CONCURRENTLY
+ 	 * is specified.
+ 	 */
+ 	if (concurrent)
+ 	{
+ 		List		*indexoidlist = RelationGetIndexList(matviewRel);
+ 		ListCell 	*indexoidscan;
+ 		bool		hasUniqueIndex = false;
+ 
+ 		foreach(indexoidscan, indexoidlist)
+ 		{
+ 			Oid			indexoid = lfirst_oid(indexoidscan);
+ 			Relation	indexRel;
+ 			Form_pg_index	indexStruct;
+ 
+ 			indexRel = index_open(indexoid, AccessShareLock);
+ 			indexStruct = indexRel->rd_index;
+ 
+ 			if (indexStruct->indisunique &&
+ 				IndexIsValid(indexStruct) &&
+ 				RelationGetIndexExpressions(indexRel) == NIL &&
+ 				RelationGetIndexPredicate(indexRel) == NIL &&
+ 				indexStruct->indnatts > 0)
+ 			{
+ 				hasUniqueIndex = true;
+ 				index_close(indexRel, AccessShareLock);
+ 				break;
+ 			}
+ 
+ 			index_close(indexRel, AccessShareLock);
+ 		}
+ 
+ 		list_free(indexoidlist);
+ 
+ 		if (!hasUniqueIndex)
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ 					 errmsg("cannot refresh materialized view \"%s\" concurrently",
+ 							quote_qualified_identifier(get_namespace_name(RelationGetNamespace(matviewRel)),
+ 													   RelationGetRelationName(matviewRel))),
+ 					 errhint("Create a unique index with no WHERE clause on one or more columns of the materialized view.")));
+ 	}
+ 
+ 	/*
  	 * The stored query was rewritten at the time of the MV definition, but
  	 * has not been scribbled on by the planner.
  	 */