Function SyncPreCheckpoint

src/backend/storage/sync/sync.c:195–213

* SyncPreCheckpoint() -- Do pre-checkpoint work * * To distinguish unlink requests that arrived before this checkpoint * started from those that arrived during the checkpoint, we use a cycle * counter similar to the one we use for fsync requests. That cycle * counter is incremented here. * * This must be called *before* the checkpoint REDO point is determined. * That ensures that we won't

 * that the checkpoint will be completed.
 */
void
SyncPreCheckpoint(void)
{
	/*
	 * Operations such as DROP TABLESPACE assume that the next checkpoint will
	 * process all recently forwarded unlink requests, but if they aren't
	 * absorbed prior to advancing the cycle counter, they won't be processed
	 * until a future checkpoint.  The following absorb ensures that any
	 * unlink requests forwarded before the checkpoint began will be processed
	 * in the current checkpoint.
	 */
	AbsorbSyncRequests();

	/*
	 * Any unlink requests arriving after this point will be assigned the next
	 * cycle counter, and won't be unlinked until next checkpoint.
	 */
	checkpoint_cycle_ctr++;
}

/*
 * SyncPostCheckpoint() -- Do post-checkpoint work