pg_clickhouse

Introduction

pg_clickhouse, an open-source PostgreSQL extension, runs analytics queries on ClickHouse right from PostgreSQL without rewriting any SQL. It supports PostgreSQL 13 and later and ClickHouse v23 and later.

Once ClickPipes starts syncing data ClickHouse, use pg_clickhouse to quickly and easily import foreign tables into a PostgreSQL schema. Then run your existing PostgreSQL queries to against those tables, preserving your existing code base while pushing execution down to ClickHouse.

Getting Started

The simplest way to try pg_clickhouse is the Docker image, which contains the standard PostgreSQL Docker image with the pg_clickhouse extension:

docker run --name pg_clickhouse -e POSTGRES_PASSWORD=my_pass \
       -d ghcr.io/clickhouse/pg_clickhouse:18
docker exec -it pg_clickhouse psql -U postgres -c 'CREATE EXTENSION pg_clickhouse'

See the tutorial to get started importing ClickHouse tables and pushing down queries.

Test Case: TPC-H

This table compares TPC-H query performance between regular PostgreSQL tables and pg_clickhouse connected to ClickHouse, both loaded at scaling factor 1; ✅ indicates full pushdown, while a dash indicates a query cancellation after 1m. All tests run on a MacBook Pro M4 Max with 36 GB of memory.

Query	Pushdown	pg_clickhouse	PostgreSQL
Query 1	✅	73ms	4478ms
Query 2		-	560ms
Query 3	✅	74ms	1454ms
Query 4	✅	67ms	650ms
Query 5	✅	104ms	452ms
Query 6	✅	42ms	740ms
Query 7	✅	83ms	633ms
Query 8	✅	114ms	320ms
Query 9	✅	136ms	3028ms
Query 10	✅	10ms	6ms
Query 11	✅	78ms	213ms
Query 12	✅	37ms	1101ms
Query 13		1242ms	967ms
Query 14	✅	51ms	193ms
Query 15		522ms	1095ms
Query 16		1797ms	492ms
Query 17		9ms	1802ms
Query 18		10ms	6185ms
Query 19		532ms	64ms
Query 20		4595ms	473ms
Query 21		1702ms	1334ms
Query 22		268ms	257ms

Compile From Source

General Unix

The PostgreSQL and curl development packages include pg_config and curl-config in the path, so you should be able to just run make (or gmake), then make install, then in your database CREATE EXTENSION http.

Debian / Ubuntu / APT

See PostgreSQL Apt for details on pulling from the PostgreSQL Apt repository.

sudo apt install \
  postgresql-server-18 \
  libcurl4-openssl-dev \
  uuid-dev \
  libssl-dev \
  make \
  cmake \
  g++

RedHat / CentOS / Yum

sudo yum install \
  postgresql-server \
  libcurl-devel \
  libuuid-devel \
  openssl-libs \
  automake \
  cmake \
  gcc

See PostgreSQL Yum for details on pulling from the PostgreSQL Yum repository.

Install From PGXN

With the above dependencies satisfied use the PGXN client (available as Homebrew, Apt and Yum packages named pgxnclient) to download, compile, and install pg_clickhouse:

pgxn install pg_clickhouse

Compile and Install

To build and install the ClickHouse library and pg_clickhouse, run:

make
sudo make install

If your host has several PostgreSQL installations, you might need to specify the appropriate version of pg_config:

export PG_CONFIG=/usr/lib/postgresql/18/bin/pg_config
make
sudo make install

If curl-config is not in the path on you host, you can specify the path explicitly:

export CURL_CONFIG=/opt/homebrew/opt/curl/bin/curl-config
make
sudo make install

If you encounter an error such as:

"Makefile", line 8: Need an operator

You need to use GNU make, which may well be installed on your system as gmake:

gmake
gmake install
gmake installcheck

If you encounter an error such as:

make: pg_config: Command not found

Be sure that you have pg_config installed and in your path. If you used a package management system such as RPM to install PostgreSQL, be sure that the -devel package is also installed. If necessary tell the build process where to find it:

export PG_CONFIG=/path/to/pg_config
make
sudo make install

To install the extension in a custom prefix on PostgreSQL 18 or later, pass the prefix argument to install (but no other make targets):

sudo make install prefix=/usr/local/extras

Then ensure that the prefix is included in the following postgresql.conf parameters:

extension_control_path = '/usr/local/extras/postgresql/share:$system'
dynamic_library_path   = '/usr/local/extras/postgresql/lib:$libdir'

Testing

To run the test suite, once the extension has been installed, run

make installcheck

If you encounter an error such as:

ERROR:  must be owner of database regression

You need to run the test suite using a super user, such as the default "postgres" super user:

make installcheck PGUSER=postgres

Loading

Once pg_clickhouse is installed, you can add it to a database by connecting as a super user and running:

CREATE EXTENSION pg_clickhouse;

If you want to install pg_clickhouse and all of its supporting objects into a specific schema, use the SCHEMA clause to specify the schema, like so:

CREATE SCHEMA env;
CREATE EXTENSION pg_clickhouse SCHEMA env;

Dependencies

The pg_clickhouse extension requires PostgreSQL 13 or higher, libcurl, libuuid. Building the extension requires a C and C++ compiler, libSSL, GNU make, and CMake.

Road Map

Our top focus is finishing pushdown coverage for analytic workloads before adding DML features. Our road map:

• Get the remaining 10 un-pushed-down TPC-H queries optimally planned
• Test and fix pushdown for the ClickBench queries
• Support transparent pushdown of all PostgreSQL aggregate functions
• Support transparent pushdown of all PostgreSQL functions
• Allow server-level and session-level ClickHouse settings via CREATE SERVER and GUCs
• Support all ClickHouse data types
• Support lightweight DELETEs and UPDATEs
• Support batch insertion via COPY
• Add a function to execute an arbitrary ClickHouse query and return its results as a tables
• Add support for pushdown of UNION queries when they all query the remote database

Authors

• David E. Wheeler
• Ildus Kurbangaliev
• Ibrar Ahmed

Copyright

• Copyright (c) 2025, ClickHouse
• Portions Copyright (c) 2023-2025, Ildus Kurbangaliev
• Portions Copyright (c) 2019-2023, Adjust GmbH
• Portions Copyright (c) 2012-2019, PostgreSQL Global Development Group