Performance: Declare exposed functions as parallel safe

[yuri0sh]

What kind of change does this PR introduce?

Performance improvement

What is the current behavior?

Postgres treats all functions as unsafe by default

What is the new behavior?

Rust appropriate

https://www.postgresql.org/docs/current/parallel-safety.html#PARALLEL-LABELING

[yuri0sh]

Setup:

create table bench_test_pg_jsonschema(
    meta jsonb
);
insert into bench_test_pg_jsonschema(meta)
select
    json_build_object(
        'a', i,
        'b', i::text
    )
from
    generate_series(1, 200000) t(i);

Query:

select count(*) from bench_test_pg_jsonschema 
where jsonb_matches_schema(
  '{"type": "object", "properties": {"a": {"type": "number", "exclusiveMinimum": 100000}, "b": {"type": "string"}}}', 
  meta
);

Default:
10630.823 ms (00:10.631)
Parallel safe:
5445.342 ms (00:05.445) - utilizes Parallel Seq Scan

MacBook Pro M1 Pro 2021, macOS 14.4, Postgres 16.2

[olirice]

nice, thank you