add pgcron + scheduling primitives to Durable

[virajmehta]

Note

Medium Risk
Adds new database schema/migration and runtime integration with pg_cron, plus queue drop behavior changes to unschedule jobs; issues here could leave orphaned jobs or break scheduling in production databases.

Overview
Adds cron scheduling to durable via pg_cron, including a new client API (setup_pgcron, create_schedule, list_schedules, delete_schedule) with validation, upsert semantics, and automatic injection of durable::scheduled_by/durable::cron headers.

Introduces a persistent schedule registry table durable.cron_schedules (with metadata/task-name indexes) and updates durable.drop_queue to remove registered schedules and best-effort unschedule matching pg_cron jobs. Also adds new DurableError variants for cron/schedule failures, re-exports the new types in lib.rs, and expands README + integration tests covering scheduling, filtering, and error cases.

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[virajmehta]

do we want to leave pgcron optional? we could make it mandatory later

[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

Autofix Details

Bugbot Autofix prepared fixes for both issues found in the latest run.

• ✅ Fixed: README uses "PostgreSQL" instead of "Postgres"
  • Updated the README line to use "Postgres" in the pg_cron integration description to match project convention.
• ✅ Fixed: Dollar-quoting breaks when content ends with tag prefix
  • Adjusted pg_literal to fall back when input ends with $durable and added a unit test covering this delimiter-boundary edge case.

Or push these changes by commenting:

@cursor push 07c4b46d0a

Preview (07c4b46d0a)

diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -326,7 +326,7 @@
 
 **Key behaviors:**
 
-- **pg_cron integration** - Schedules are backed by PostgreSQL's pg_cron extension. At each tick, pg_cron inserts a task into the queue via `durable.spawn_task()`, and workers pick it up normally.
+- **pg_cron integration** - Schedules are backed by Postgres's pg_cron extension. At each tick, pg_cron inserts a task into the queue via `durable.spawn_task()`, and workers pick it up normally.
 - **Upsert semantics** - Calling `create_schedule` with an existing name updates the schedule in place.
 - **Origin tracking** - Scheduled tasks automatically receive `durable::scheduled_by` and `durable::cron` headers, so tasks can identify how they were spawned.
 - **Metadata filtering** - Attach arbitrary JSON metadata to schedules and filter with JSONB containment queries.

diff --git a/src/cron.rs b/src/cron.rs
--- a/src/cron.rs
+++ b/src/cron.rs
@@ -504,9 +504,10 @@
 // --- SQL escaping ---
 
 /// Dollar-quote a string using `$durable$` as the delimiter.
-/// Falls back to escaped single quotes if the content contains `$durable$`.
+/// Falls back to escaped single quotes if the content contains `$durable$`
+/// or ends with `$durable` (which would collide with the closing delimiter).
 fn pg_literal(s: &str) -> String {
-    if !s.contains("$durable$") {
+    if !s.contains("$durable$") && !s.ends_with("$durable") {
         format!("$durable${s}$durable$")
     } else {
         // Fallback: single-quote escaping (double up any single quotes)
@@ -725,6 +726,12 @@
         assert_eq!(pg_literal(content), "'has $durable$ and ''quotes'''");
     }
 
+    #[test]
+    fn test_pg_literal_fallback_when_content_ends_with_delimiter_prefix() {
+        let content = "test$durable";
+        assert_eq!(pg_literal(content), "'test$durable'");
+    }
+
     // --- Schedule name validation tests ---
 
     #[test]

_{This Bugbot Autofix run was free. To enable autofix for future PRs, go to the Cursor dashboard.}

[cursor]

README uses "PostgreSQL" instead of "Postgres"

Low Severity

The newly added line uses "PostgreSQL's pg_cron extension" instead of the preferred "Postgres's pg_cron extension", violating the project convention to prefer "Postgres" over "PostgreSQL" in documentation.

 

^{Triggered by team rule: Prefer "Postgres" instead of PostgreSQL"}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

[cursor]

Error message uses ticks instead of backticks

Low Severity

The error message in pg_literal wraps the technical term $durable with single quotes ('$durable') instead of backticks, which violates the project convention for wrapping technical terms.

 

^{Triggered by team rule: Prefer backticks (`) instead of ticks (') to wrap technical terms}