Support PostgreSQL array created using array internal type name

presto-postgresql/src/main/java/io/prestosql/plugin/postgresql/PostgreSqlClient.java

@@ -219,13 +219,14 @@ private Map<String, Integer> getArrayColumnDimensions(Connection connection, Jdb
             return ImmutableMap.of();
         }
         String sql = "" +
-                "SELECT att.attname, att.attndims " +
+                "SELECT att.attname, greatest(att.attndims, 1) AS attndims " +
                 "FROM pg_attribute att " +
+                "  JOIN pg_type attyp ON att.atttypid = attyp.oid" +
                 "  JOIN pg_class tbl ON tbl.oid = att.attrelid " +
                 "  JOIN pg_namespace ns ON tbl.relnamespace = ns.oid " +
                 "WHERE ns.nspname = ? " +
                 "AND tbl.relname = ? " +
-                "AND att.attndims > 0 ";
+                "AND attyp.typcategory = 'A' ";
         try (PreparedStatement statement = connection.prepareStatement(sql)) {
             statement.setString(1, tableHandle.getSchemaName());
             statement.setString(2, tableHandle.getTableName());

presto-postgresql/src/test/java/io/prestosql/plugin/postgresql/TestPostgreSqlTypeMapping.java

@@ -336,9 +336,10 @@ public void testArray()
     @Test
     public void testInternalArray()
     {
-        // One can declare column using internal type name for an array. Such a column is not recognized
-        // as array in Presto, because it does not have correct value in pg_attribute.attndims.
-        testUnsupportedDataType("_int4");
+        DataTypeTest.create()
+                .addRoundTrip(arrayDataType(integerDataType(), "_int4"), asList(1, 2, 3))
+                .addRoundTrip(arrayDataType(varcharDataType(), "_text"), asList("a", "b"))
+                .execute(getQueryRunner(), postgresCreateAndInsert("tpch.test_array_with_native_name"));
     }
 
     @Test