Function TestForOldSnapshot

src/include/storage/bufmgr.h:300–312

* Check whether the given snapshot is too old to have safely read the given * page from the given table. If so, throw a "snapshot too old" error. * * This test generally needs to be performed after every BufferGetPage() call * that is executed as part of a scan. It is not needed for calls made for * modifying the page (for example, to position to the right place to insert a * new index tup

 * exclude a page from old snapshot testing near the front.
 */
static inline void
TestForOldSnapshot(Snapshot snapshot, Relation relation, Page page)
{
	Assert(relation != NULL);

	if (old_snapshot_threshold >= 0
		&& (snapshot) != NULL
		&& ((snapshot)->snapshot_type == SNAPSHOT_MVCC
			|| (snapshot)->snapshot_type == SNAPSHOT_TOAST)
		&& !XLogRecPtrIsInvalid((snapshot)->lsn)
		&& PageGetLSN(page) > (snapshot)->lsn)
		TestForOldSnapshot_impl(snapshot, relation);
}

#endif							/* FRONTEND */