PostgreSQL-ZetaSketch brings Google BigQuery HLL++ compatible functions to PostgreSQL.
Run in Docker
docker run --name some-postgres -e POSTGRES_PASSWORD=mysecretpassword -d study/postgresql-zetasketchdocker run --name some-postgres -e POSTGRES_PASSWORD=mysecretpassword -d study/postgresql-zetasketch docker exec -it some-postgres psql -U postgres postgres=# SELECT HLL_COUNT.MERGE(respondents_hll) AS num_respondents, flavor FROM ( SELECT HLL_COUNT.INIT(respondent) AS respondents_hll, flavor, country FROM ( SELECT * FROM ( VALUES (1, 'Vanilla', 'CH'), (1, 'Chocolate', 'CH'), (2, 'Chocolate', 'US'), (2, 'Strawberry', 'US')) AS t(respondent, flavor, country)) as foo GROUP BY flavor, country) as bar GROUP BY flavor; num_respondents | flavor -----------------+------------ 1 | Strawberry 1 | Vanilla 2 | Chocolate (3 rows) $ git clone https://github.com/tada/pljava.git $ cd pljava $ git checkout tags/V1_5_5 $ mvn -Pwnosign clean install $ cd ..$ git clone https://github.com/phstudy/postgresql-zetasketch.git $ mvn -f postgresql-zetasketch/pom.xml clean package