pg_grammar_guard

pg_grammar_guard : Catalog-derived grammars and approved grammar drift checks

Overview

Packages

Source

pig build pkg pg_grammar_guard;		# 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_grammar_guard;		# install via package name, for the active PG version

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

Create this extension with:

CREATE EXTENSION pg_grammar_guard CASCADE; -- requires pg_living_assertions

Usage

Sources:

• PGXN 0.4.1

pg_grammar_guard generates GBNF or JSON Schema from catalog identifiers and detects drift from approved grammars. It is pure SQL, needs no preload and is packaged for PostgreSQL 14–18. Its control file requires pg_living_assertions.

Generate a grammar

CREATE EXTENSION pg_grammar_guard CASCADE;
CREATE TABLE public.grammar_demo (id integer, label text);
SELECT grammar_guard.grammar_for_json(ARRAY[
  ROW('column', 'enum',
      grammar_guard.catalog_columns('public.grammar_demo'), true)
]::grammar_guard.grammar_field[]);

The catalog helpers enumerate actual tables, columns and enum labels. Generation supports nested objects and bounded arrays; open-ended values such as arbitrary SQL or file paths need separate validation.

Detect changes

grammar_guard.watch() stores the query that rebuilds a grammar, and grammar_guard.check_grammar() evaluates it against the live catalog. Results and their age are available through living_assertions.status.

Register baseline SQL only through trusted administrators. A grammar limits valid identifiers; it cannot prove that a selected table, join or answer is semantically correct. Baselines from the old 0.2 series lack the original generating query and require manual re-approval when upgrading.