feat: add Idempotency to Postgres (#7750)

README.md

@@ -525,9 +525,26 @@ let api = new ParseServer({
 | `idempotencyOptions.paths` | yes      | `Array<String>` | `[]`          | `.*` (all paths, includes the examples below), <br>`functions/.*` (all functions), <br>`jobs/.*` (all jobs), <br>`classes/.*` (all classes), <br>`functions/.*` (all functions), <br>`users` (user creation / update), <br>`installations` (installation creation / update) | PARSE_SERVER_EXPERIMENTAL_IDEMPOTENCY_PATHS   | An array of path patterns that have to match the request path for request deduplication to be enabled. The mount path must not be included, for example to match the request path `/parse/functions/myFunction` specify the path pattern `functions/myFunction`. A trailing slash of the request path is ignored, for example the path pattern `functions/myFunction` matches both `/parse/functions/myFunction` and `/parse/functions/myFunction/`. |
 | `idempotencyOptions.ttl`   | yes      | `Integer`       | `300`         | `60` (60 seconds)                                                                                                                                                                                                                                                           | PARSE_SERVER_EXPERIMENTAL_IDEMPOTENCY_TTL     | The duration in seconds after which a request record is discarded from the database. Duplicate requests due to network issues can be expected to arrive within milliseconds up to several seconds. This value must be greater than `0`.                                                                                                                                                                                                              |
 
-### Notes <!-- omit in toc -->
+### Postgres <!-- omit in toc -->
 
-- This feature is currently only available for MongoDB and not for Postgres.
+To use this feature in Postgres, you will need to create a cron job using [pgAdmin](https://www.pgadmin.org/docs/pgadmin4/development/pgagent_jobs.html) or similar to call the Postgres function `idempotency_delete_expired_records()` that deletes expired idempotency records. You can find an example script below. Make sure the script has the same privileges to log into Postgres as Parse Server.
+
+```bash
+#!/bin/bash
+
+set -e
+psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-EOSQL
+    SELECT idempotency_delete_expired_records();
+EOSQL
+
+exec "$@"
+```
+
+Assuming the script above is named, `parse_idempotency_delete_expired_records.sh`, a cron job that runs the script every 2 minutes may look like:
+
+```bash
+2 * * * * /root/parse_idempotency_delete_expired_records.sh >/dev/null 2>&1
+```
 
 ## Localization