deparser: ON DELETE SET NULL (column_list) loses its column list

[jasdeepkhalsa]

Summary

pgsql-deparser drops the optional column list from ON DELETE SET NULL (...) and ON DELETE SET DEFAULT (...). The output is still valid SQL, but it means something different from the input — the referential action is silently widened from specific columns to all foreign key columns.

The column list on SET NULL / SET DEFAULT was added in PostgreSQL 15.

Versions

• pgsql-deparser@18.3.6
• plpgsql-parser@18.5.8
• libpg-query@18.1.4
• Node 24

Reproduction

import { parse } from 'plpgsql-parser'
import { deparse } from 'pgsql-deparser'
import { loadModule } from 'libpg-query'
await loadModule()

const sql = `ALTER TABLE ONLY child ADD CONSTRAINT child_fk FOREIGN KEY (a, b) REFERENCES parent(a, b) ON DELETE SET NULL (b);`
console.log(await deparse((await parse(sql)).sql))

Expected

ALTER TABLE ONLY child ADD CONSTRAINT child_fk FOREIGN KEY (a, b) REFERENCES parent (a, b) ON DELETE SET NULL (b);

Actual

ALTER TABLE ONLY child ADD CONSTRAINT child_fk FOREIGN KEY(a, b) REFERENCES parent (a, b) ON DELETE SET NULL;

SET DEFAULT behaves the same way:

in : ... ON DELETE SET DEFAULT (b);
out: ... ON DELETE SET DEFAULT;

The parse tree is correct

Constraint keys: contype, conname, is_enforced, initially_valid, pktable,
                 fk_attrs, pk_attrs, fk_matchtype, fk_upd_action,
                 fk_del_action, fk_del_set_cols, location

fk_del_set_cols: [{"String":{"sval":"b"}}]
fk_del_action  : "n"

fk_del_set_cols is populated but does not appear to be consulted when rendering the ON DELETE clause.

Impact

This one is quiet — the output parses and applies cleanly, so nothing surfaces at apply time. The difference only shows up later, when a delete nulls more columns than the original schema intended.