PostgreSQL: support FOR NO KEY UPDATE and FOR KEY SHARE row-locking clauses #2778

Summary

PostgreSQL's row-locking clause has four lock strengths: FOR UPDATE, FOR NO KEY UPDATE, FOR SHARE and FOR KEY SHARE. sqlparser reads only FOR UPDATE and FOR SHARE. FOR NO KEY UPDATE and FOR KEY SHARE, which PostgreSQL's own referential-integrity triggers use (SELECT 1 FROM ONLY t x WHERE … FOR KEY SHARE OF x), are rejected.

Reproduction (current main, c6cec56)

use sqlparser::{dialect::PostgreSqlDialect, parser::Parser};

Parser::parse_sql(&PostgreSqlDialect {}, "SELECT id FROM t WHERE id = 1 FOR NO KEY UPDATE").unwrap();
Parser::parse_sql(&PostgreSqlDialect {}, "SELECT id FROM t WHERE id = 1 FOR KEY SHARE OF t").unwrap();

sql parser error: Expected: one of UPDATE or SHARE, found: NO at Line: 1, Column: 35
sql parser error: Expected: one of UPDATE or SHARE, found: KEY at Line: 1, Column: 35

SELECT id FROM t WHERE id = 1 FOR SHARE OF t SKIP LOCKED parses. All of these run on PostgreSQL (checked on 17.11):

CREATE TABLE t (id int PRIMARY KEY);
SELECT id FROM t WHERE id = 1 FOR NO KEY UPDATE;
SELECT id FROM t WHERE id = 1 FOR KEY SHARE OF t;
SELECT id FROM t FOR KEY SHARE NOWAIT;
SELECT id FROM t FOR NO KEY UPDATE SKIP LOCKED;

Grammar

From https://www.postgresql.org/docs/current/sql-select.html#SQL-FOR-UPDATE-SHARE:

FOR lock_strength [ OF from_reference [, ...] ] [ NOWAIT | SKIP LOCKED ]

where lock_strength can be one of
    UPDATE
    NO KEY UPDATE
    SHARE
    KEY SHARE

Proposed change

Add two variants to LockType, for example NoKeyUpdate and KeyShare, displayed as NO KEY UPDATE and KEY SHARE. Parse them in parse_lock, where FOR is followed by NO KEY UPDATE or KEY SHARE, in the PostgreSQL and generic dialects. OF …, NOWAIT and SKIP LOCKED then follow as they do for the other two strengths. Round-trip tests for each strength, with and without OF and the wait policy, would cover it.

This is independent of FROM ONLY t, which the same trigger queries use and #2770 addresses.