PL/PRQL is a PostgreSQL extension that lets you write functions with PRQL. The extension supports PostgreSQL v12-16 on Linux and macOS.
PRQL (Pipelined Relational Query Language) is an open source query language for data manipulation and analysis that compiles to SQL. PRQL introduces a pipeline concept (similar to Unix pipes) that transforms data line-by-line. The sequential series of transformations reduces the complexity often encountered with nested SQL queries and makes your data manipulation logic easier to read and write.
- Write functions with PRQL - Useful for large analytical queries
- PRQL compiler - Useful for development and debugging
- Inline execution - Useful for prototyping and custom queries in ORMs
PRQL shines when your SQL queries becomes very long and complex. You can manage this complexity by porting your most impressive SQL incantations to PRQL functions, which can then be used in dashboards, business logic or other database code. For example:
create function match_stats(int) returns table(player text, kd_ratio float) as $$
from matches
filter match_id == $1
group player (
aggregate {
total_kills = sum kills,
total_deaths = sum deaths
}
)
filter total_deaths > 0
derive kd_ratio = total_kills / total_deaths
select { player, kd_ratio }
$$ language plprql;
select * from match_stats(1001)
player | kd_ratio
---------+----------
Player1 | 0.625
Player2 | 1.6
(2 rows)
This is similar to how PL/Python, PL/Javascript, and PL/Rust are implemented.
You can use prql_to_sql()
to see the SQL statements that PostgreSQL executes under the hood. This function invokes the PRQL compiler and shows you the resulting SQL code. Using the example above:
select prql_to_sql('...'); -- statements above omitted for brevity
prql_to_sql
-------------
WITH table_0 AS (
SELECT player, COALESCE(SUM(kills), 0) AS _expr_0, COALESCE(SUM(deaths), 0) AS _expr_1
FROM matches
WHERE match_id = $1
GROUP BY player
)
SELECT player, _expr_0 / _expr_1 AS kd_ratio
FROM table_0
WHERE _expr_1 > 0
-- Generated by PRQL compiler version:0.11.1 (https://prql-lang.org)
(1 row)
You can run PRQL code directly with the prql
function. This is useful for e.g. custom queries in ORMs:
select prql('from matches | filter player == ''Player1''')
as (id int, match_id int, round int, player text, kills int, deaths int)
limit 2;
id | match_id | round | player | kills | deaths
----+----------+-------+---------+-------+--------
1 | 1001 | 1 | Player1 | 4 | 1
3 | 1001 | 2 | Player1 | 1 | 7
(2 rows)
-- Same as above, but returns cursor
select prql('from matches | filter player == ''Player1''', 'player1_cursor');
fetch 2 from player1_cursor;
For more information on the design of the extension, see the design document.
For more information on PRQL, visit the PRQL website, playground or repository.
Note
PRQL supports select
statements only. insert
, update
, and delete
statements, and your other database code, will continue to live in vanilla SQL, ORMs, or other database frameworks.
The following installation guides work on Ubuntu and Debian.
Follow these steps to install PL/PRQL from one of the released deb files:
-
Download the deb file that matches your operating system from the Releases page.
-
Open a terminal and change to the directory where the
.deb
file was downloaded. Install the package with dpkg, e.g.:sudo dpkg -i plprql-0.1.0-postgresql-16-debian-bookworm-amd64.deb
-
If dpkg reports missing dependencies, run the following command to fix them:
sudo apt-get install -f
This only requires that you have PostgreSQL installed on beforehand. Replace the major version of PostgreSQL in the deb's filename if needed. Supported versions are 12, 13, 14, 15, and 16.
Make sure you have the following prerequisites installed (apt package names in parentheses):
- PostgreSQL (
postgresql-16
) - PostgreSQL server headers (
postgresql-server-dev-16
) - A C compiler (
clang
) - Utilities for the shell script (
curl
,wget
,gnupg
,lsb-release
,git
,jq
) - Cargo and pgrx:
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y source ~/.bashrc cargo install --locked --version=0.11.3 cargo-pgrx
Run the following command to download and execute the shell script in scripts/install.sh:
curl --proto '=https' --tlsv1.2 -sSf https://raw.githubusercontent.com/kaspermarstal/plprql/main/scripts/install.sh | bash
This will install the tip of the main branch using pg_config
on your path.
You can customize the PostgreSQL installation and/or the PL/PRQL version using the --pg-config
and --revision
flags:
curl --proto '=https' --tlsv1.2 -sSf https://raw.githubusercontent.com/kaspermarstal/plprql/main/scripts/install.sh > install.sh
chmod +x ./install.sh
./install.sh --pg-version /usr/bin/pg_config --revision 186faea
PL/PRQL is built on top of the pgrx framework for writing PostgreSQL extensions in Rust. This framework comes with development tools that you need to install. Follow these steps to set up your development environment:
-
Install
cargo
.curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
-
Install
cargo-pgrx
.cargo install --locked --version=0.11.3 cargo-pgrx
The version of
cargo-pgrx
must match the version ofpgrx
inplprql/Cargo.toml
. -
Initialize
pgrx
for your system.cargo pgrx init --pg16 <PG16>
where
<PG16>
is the path to your system installation'spg_config
tool (typically/usr/bin/pg_config
). Supported versions are PostgreSQL v12-16. You can also runcargo pgrx init
and havepgrx
download, install, and compile PostgreSQL v12-16. These installations are managed bypgrx
and used for development and testing. Individualpgrx
-managed installations can be installed using e.g.cargo pgrx init --pg16 download
. -
Clone this repository.
git clone https://github.com/kaspermarstal/plprql
-
cd
into root directory and install the extension to the PostgreSQL specified by thepg_config
currently on your$PATH
.cd plprql/plprql cargo pgrx install --release
You can target a specific PostgreSQL installation by providing the path of another
pg_config
using the-c
flag. -
Fire up your system PostgreSQL installation and start writing functions right away! You can also try out PL/PRQL in an installation managed by
pgrx
:$ cargo pgrx run pg16 psql> create extension plprql; psql> create function match_stats(int) returns table(total_kills real, total_deaths real) as $$ from rounds filter match_id == $1 aggregate { total_kills = sum kills, total_deaths = sum deaths } $$ language plprql psql> select match_stats(1);
Run these commands to install PL/PRQL and all of its dependencies for PostgreSQL 16:
sudo apt-get update && apt-get upgrade
sudo apt-get install -y curl wget gnupg lsb-release git build-essential
sh -c 'echo "deb https://apt.postgresql.org/pub/repos/apt $(lsb_release -cs)-pgdg main" > /etc/apt/sources.list.d/pgdg.list'
wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add -
sudo apt-get update
sudo apt-get install -y postgresql-16 postgresql-server-dev-16
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
source ~/.bashrc
cargo install --locked --version=0.11.3 cargo-pgrx
cargo pgrx init --pg16 $(which pg_config)
git clone https://github.com/kaspermarstal/plprql
cd plprql/plprql
cargo pgrx install --no-default-features --release --sudo
You can try this out in a vanilla docker container using docker run -it --entrypoint /bin/bash debian:bookworm
and copying the code above into the terminal. You must remove all references to sudo as commands in docker are already running as root.
You can run tests using cargo pgrx test pg16
. Unit tests are in the main plprql
crate while integration tests are in the plprql-tests
crate. From the root source directory:
cd plprql && echo "\q" | cargo pgrx run pg16 && cargo test --no-default-features --features pg16
cd ../plprql-tests && echo "\q" | cargo pgrx run pg16 && cargo test --no-default-features --features pg16
Supported PostgreSQL versions are pg12
, pg13
, pg14
, pg15
, and pg16
.
Apache 2.0 License