Changing pg_trgm.similarity_threshold in RDS

Hello AWS Customer,

As you know, the parameters for the 'pgtrgm' extension are non-standard i.e. they are not part of a standard postgresq.conf file. In RDS, we provide parameter group to enable PostgreSQL parameters, however, at present, 'pg_trgm' extension GUC parameters (given below), are not part of default parameter group of RDS PostgreSQL instance: pg_trgm.similarity_threshold, pg_trgm.word_similarity_threshold, pg_trgm.strict_word_similarity_threshold

So, you will not be able to change the values of these parameters at global level for the RDS instance.

But workaround here would be to set this parameter value at the database session level using the below set command:

"set pg_trgm.similarity_threshold=0.1;
"

However, the changed parameter value is valid only for the session executing the query. When a new session connects to the DB, the "pg_trgm.similarity_threshold" parameter value is set to "0.3" by default.

The internal team is already working towards incorporating this feature in RDS PostgreSQL but I don't have any ETA on its availability. Please follow the AWS blog for new feature announcements

Hope the information helps.