29b45dd234
- Adds `skills/postgres-best-practices/`: A new skill containing comprehensive Postgres performance optimization rules and guidelines from Supabase. - The skill includes rules for query performance, connection management, security (RLS), and schema design. - Updates `README.md` to include the new skill in the directory.
1.5 KiB
1.5 KiB
title, impact, impactDescription, tags
| title | impact | impactDescription | tags |
|---|---|---|---|
| Use Advisory Locks for Application-Level Locking | MEDIUM | Efficient coordination without row-level lock overhead | advisory-locks, coordination, application-locks |
Use Advisory Locks for Application-Level Locking
Advisory locks provide application-level coordination without requiring database rows to lock.
Incorrect (creating rows just for locking):
-- Creating dummy rows to lock on
create table resource_locks (
resource_name text primary key
);
insert into resource_locks values ('report_generator');
-- Lock by selecting the row
select * from resource_locks where resource_name = 'report_generator' for update;
Correct (advisory locks):
-- Session-level advisory lock (released on disconnect or unlock)
select pg_advisory_lock(hashtext('report_generator'));
-- ... do exclusive work ...
select pg_advisory_unlock(hashtext('report_generator'));
-- Transaction-level lock (released on commit/rollback)
begin;
select pg_advisory_xact_lock(hashtext('daily_report'));
-- ... do work ...
commit; -- Lock automatically released
Try-lock for non-blocking operations:
-- Returns immediately with true/false instead of waiting
select pg_try_advisory_lock(hashtext('resource_name'));
-- Use in application
if (acquired) {
-- Do work
select pg_advisory_unlock(hashtext('resource_name'));
} else {
-- Skip or retry later
}
Reference: Advisory Locks