# 66.7. Examples

The core PostgreSQL distribution includes the GIN operator classes previously shown in [Table 64.1](https://www.postgresql.org/docs/10/static/gin-builtin-opclasses.html#GIN-BUILTIN-OPCLASSES-TABLE). The following `contrib` modules also contain GIN operator classes:

`btree_gin`

B-tree equivalent functionality for several data types

`hstore`

Module for storing (key, value) pairs

`intarray`

Enhanced support for `int[]`

`pg_trgm`

Text similarity using trigram matching