Introducing pg_clickhouse: A Postgres extension for querying ClickHouse

ClickHouse released pg_clickhouse v0.1.0, an Apache 2-licensed PostgreSQL extension that enables transparent execution of analytics queries on ClickHouse directly from PostgreSQL. Built on the foundation of clickhouse_fdw, the extension addresses the challenge of migrating analytical queries when moving workloads from PostgreSQL to ClickHouse. Key features include advanced query pushdown capabilities, support for ordered-set aggregates like percentile_cont(), SEMI JOIN pushdown, and transparent conversion of PostgreSQL aggregate FILTER expressions to ClickHouse combinators. Testing with TPC-H benchmarks shows 21 of 22 queries execute efficiently with 12 achieving full pushdown. The roadmap includes completing pushdown coverage for all analytic workloads, supporting all ClickHouse data types, and adding DML features.