fix: skip recorder and sqlite state creation when vchord extension is not created

When vchord is added to shared_preload_libraries without running
CREATE EXTENSION, the object_access_hook fires on any DROP TABLE
or DROP DATABASE and calls the recorder's get() function, which
lazily creates the pgsql_tmp_vchord_sampling/ directory and SQLite
files under PGDATA.

This is unnecessary and confusing when looking at contents of PGDATA
and seeing files from an extension that has never been enabled

The commit skips all recorder operations when the extension has never
been created (extension does not have an assigned OID)

Author: Ngalstyan4

src/recorder/worker.rs

@@ -32,6 +32,12 @@ fn get<'a>() -> Option<RefMut<'a, rusqlite::Connection>> {
     if database_oid == 0 {
         return None;
     }
+    // Skip if vchord extension is not installed in this database
+    if unsafe { pgrx::pg_sys::get_extension_oid(c"vchord".as_ptr(), true) }
+        == pgrx::pg_sys::InvalidOid
+    {
+        return None;
+    }
     let mut connection = CONNECTION.borrow_mut();
     if connection.is_none()
         && let Err(err) = || -> rusqlite::Result<()> {