pg_liquid

pg_liquid : Liquid-inspired Datalog graph query extension for PostgreSQL

Overview

Packages

Source

pig build pkg pg_liquid;		# build rpm/deb

Install

Make sure PGDG and PIGSTY repo available:

pig repo add pgsql -u   # add both repo and update cache

Install this extension with pig:

pig install pg_liquid;		# install via package name, for the active PG version

pig install pg_liquid -v 18;   # install for PG 18
pig install pg_liquid -v 17;   # install for PG 17
pig install pg_liquid -v 16;   # install for PG 16
pig install pg_liquid -v 15;   # install for PG 15
pig install pg_liquid -v 14;   # install for PG 14

Create this extension with:

CREATE EXTENSION pg_liquid;

Usage

Source: Docs site, README, Release v0.1.7, SQL install script

pg_liquid brings Liquid-style graph and compound queries into PostgreSQL. It stores graph state in the liquid schema and exposes SQL entry points for plain queries, principal-bound queries, and least-privilege reads.

Core query surface

CREATE EXTENSION pg_liquid;

SELECT *
FROM liquid.query($$
  Edge("a","b").
  Edge("b","c").
  Path(X,Y) :- Edge(X,Y).
  Path(X,Y) :- Edge(X,Z), Path(Z,Y).
  Path("a",Y)?
$$) AS t(y text);

• liquid.query(program text): executes Liquid facts, rules, and one terminal query.
• liquid.query_as(principal text, program text): principal-bound execution.
• liquid.read_as(principal text, program text): least-privilege read wrapper; intended for application-facing reads.

Language and modeling features

• facts and rules terminated by .
• one terminal ? query per program
• graph edges via Edge(...)
• typed compounds such as Type@(role=value, ...)
• query-local recursive rules
• built-in policy compounds such as CompoundReadByRole and liquid/acts_for

Row normalizers

SELECT liquid.create_row_normalizer(
  'account_profiles'::regclass,
  'account_profile_normalizer',
  'AccountProfile',
  '{"account_id":"id","display_name":"display_name","tier":"tier"}'::jsonb,
  true
);

• liquid.create_row_normalizer(...): projects relational rows into Liquid compounds.
• liquid.rebuild_row_normalizer(...): regenerates bindings after table changes.
• liquid.drop_row_normalizer(...): removes the normalizer and optionally purges generated bindings.

Caveats

• Upstream validates the extension on PostgreSQL 14 through 18.
• query_as and read_as are revoked from PUBLIC in the shipped SQL; grant them deliberately.
• read_as(...) is the safer application entry point when clients should not assert new facts.