Custom Dialect 관련 질문있습니다.

안녕하세요.

저는 기본문법에서 Custom Dialect로 세팅 뒤 group_concat을 사용하는 부분을 듣고있는데요.

아래와 같은 에러가 발생해서 질문드립니다.

현재 세팅에서는 Gradle과 Postgresql 을 사용중인데요.

호출한 query는 아래와 같고,

String query = "select group_concat(m.username) From Member m";

Custom Dialect 구현체는 다음과 같습니다.

public MyPostDialect() {
    super();
    this.registerFunction("group_concat", new StandardSQLFunction("group_concat", new StringType()));
}

ERROR: ERROR: function group_concat(character varying) does not exist

  Hint: No function matches the given name and argument types. You might need to add explicit type casts.

  Position: 60

javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: could not extract ResultSet

at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:154)

at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1613)

at org.hibernate.query.Query.getResultList(Query.java:165)

at jpql.JpaMain.main(JpaMain.java:41)

Caused by: org.hibernate.exception.SQLGrammarException: could not extract ResultSet

at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:103)

at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)

at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:113)

at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:99)

at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:67)

at org.hibernate.loader.Loader.getResultSet(Loader.java:2297)

at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:2050)

at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:2012)

at org.hibernate.loader.Loader.doQuery(Loader.java:948)

at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:349)

at org.hibernate.loader.Loader.doList(Loader.java:2843)

at org.hibernate.loader.Loader.doList(Loader.java:2825)

at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2657)

at org.hibernate.loader.Loader.list(Loader.java:2652)

at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:506)

at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:400)

at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:219)

at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1414)

at org.hibernate.query.internal.AbstractProducedQuery.doList(AbstractProducedQuery.java:1636)

at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1604)

... 2 more

Caused by: org.postgresql.util.PSQLException: ERROR: function group_concat(character varying) does not exist

  Hint: No function matches the given name and argument types. You might need to add explicit type casts.

  Position: 60

혹시 어느 부분을 수정해야되는지 알 수 있을까요 ?